THE BIOLOGICAL E OARD OF CANADA

UNDER THE rONTROL OF

THE HON. THE MINISTER OF FISHERIES

BULLETIN r\Jo. XXXVII

THE INDUSTRIAL CHEMISTRY OF FISH OILS WITH PARTICULAR REFERENCE TO THOSE OF BRITISH COLUMBIA

BY H. N. BROCKLESBY AND O. F. DENSTEDT Fisheries Experiment;al Station (Pacific)

(Foreword by J. J. Cowie)

OTTAiWA 1933 n

II THE BIOLOGICAL BOARD OF CANADA

UNDER THE CONTROL OF THE HON. THE MINISTER OF FISHERIES

BULLETIN No. XXXVII

THE INDUSTRIAL CHEMISTRY OF FISH OILS WITH PARTICULAR REFERENCE TO THOSE OF BRITISH COLUMBIA

BY H. N. BROCKLESBY AND

O. F. DENSTEDT Fisheries Experimental Station (Pacific)

(Foreword by ]. ]. Cowie)

OTTAWA 1933 The series of Bulletins is designed for the presentation in non-technical form oj subjects of interest to the general public, in particular that related to the fishing industry. FOREWORD

In a normal year over five million gallons of oil of various kinds are recovered from fish and marine animals caught by Canadian fishermen. Three-fifths of that quantity is procured from pilchards taken on the outer coast of Vancouver island, British Columbia. The production of oil from pilchards has developed only within the past seven years. A great dealof useful research on British Columbia fish oils has been carried on at the Board's Experimental Station at Prince Rupert. But, while research generally has already furnished us with much knowledge of the commercial uses to which certain of these oils are and may yet be put, the information has not been made so available to tIle industry, at least, as it should be, in view of the great increase in the output of the product in recent years and the need for finding new and wider outlets for it. I t was, therefore, felt that a short, comprehensive resume and discussion of what has been done and is at present being done through research towards widening the industrial use of fish oils would be of value not only to those engaged in the production of fish oils but to those who use oils of various kinds in their manufacturing processes and to farmers and feeders of cattle, pigs, and poultry. With this end in view the Board authorized Mr. H. N. Brocklesby, with the assistance of Mr. O. F. Denstedt of the staffof the Fisheries Experimental Station at Prince Rupert, to put together fqr publication the scattered information con-­ tained in the literature on this subject in addition to the results of their own researches. That has now been accomplished and their work is presented in the form of this bulletin. It contains a great amount of information on fats and oils, and I feel sure that the fishing industry on both coasts will find the sections which deal particularly with fish oils not only informative but of real economic value.

]. J. COWIE, Secretary-Treasurer, Biological Board of Canada. Ottawa, December 30th, 1932.

3

CONTENTS

SECTION I THE GENERAL CHEMISTRY OF FATS

SECTION I! THE PROPERTIES OF FATS AND OILS

PAGE Oxidation ...... 21

An tioxidan ts ...... 23 Action of light ...... 24 Hydrolysis or saponification.. . 25

Rancidity ...... 25

Bacteria and moulds...... 26

Polymerization...... 27

Hydrogenation...... 31

SuIphona tion ...... 33

Sulphuration...... 39

SECTION II! COMPOSITION AND OCCURRENCE OF FATS AND OILS

Vegetable fats and oils...... 39 Terrestrial animal fats and oils. 40 Marine animal and fish oils. 41

Blubber oils...... 41

Fish oils ...... 43

Stearine ...... 44

Unsaponifiable matter...... 45

SECTION IV PRODUCTION OF FISH OILS

PRODUCTION

Fish liver oils ...... 51

Rotting process...... 51 Direct steam process ...... 52

Vacuum methods ...... 52 Freezing methods...... 52

Electrolytic method...... 54 5 Fish body oils ...... 55

Discontinuous batch system ...... 55 Continuous system ...... 57

Cooking and pressing ...... 57 Separation of oil...... 58

Settling tank system ...... 58 Separating by centrifuging ...... 59

Miscellaneous methods of oil and meal recovery ...... 62

Solvent extraction process ...... 63

General ...... 63 Horizon tal extractors ...... 66

Vertical percolating extractors ...... 69

Oily fish offal...... 71

REFINING

Wintering of fish oils ...... 72

Alkali refining...... 73

Bleaching...... 76

Deodorizing ...... 77

Hardening ...... '" ...... 78

Preparation of catalyst ...... 79

Hardening process ...... 80 Removal of catalysts ...... 81

Continuous hydrogenation ...... 81

SECTION V UTILIZATION OF FISH OILS

Introduction ...... 87 Fish oils as foods ...... 87

Hardened fish oils ...... 89

Special fats ...... 90

Shortenings ...... 90

Margarine ...... , ...... 91

Confectionery fats ...... 91

Frying fats ...... 91

Salad oils ...... 92

Nutritive value of hardened fats ...... 92

Medicinal uses ...... 93

Cod liver oil ...... 93

Vitamin potency of other fish oils ...... 94

Fish oils in soaps ...... 97

Nature of fish oil soaps ...... 98

Odour ...... 98 Soaps from hydrogenated oils ...... 99 Soaps from polymerized oils ...... 99

6 Soaps from sulphonated oils ...... 100

Other soaps ...... 100

Fish oils in protective coatings...... 101 Nature of drying oil films...... 101

Processing fish oils for paints ...... 103 Refrigeration and refining...... 103 Polymerization ...... 103 By heating ...... 103 " blowing ...... 104 " simultaneous polymerization and steam distillation ...... 105

Miscellaneous methods of polymerization ...... 105 Sulphurization ...... 105

Condensation with ZnCb ...... 105 Ozonization ...... 106 Ultra violet light ...... 106

Use of driers and pigments ...... 106

Boiled oils ...... ; ...... 106

Driers ...... 106 Effect of driers on filmproperties ...... 107 Influence of pigments on drying films ...... 108

Fish oil paints ...... 109 Flexible coatings...... 110

Patent leather, enamelled leather ...... 110 Oiled fabrics ...... 111 Linoleum and floor cloths...... 111

Fish oils in tanning...... 111 Fat stuffing ...... 111

Chamois tanning...... 112 Fish oils in lubrication ...... 1 13 Properties of lubricating oils ...... 113

Spindle and light oils...... 1 14

Blended oils ...... 115 Greases and solid lubricants...... 115

Cutting oils ...... : ...... 116 Processing for lubricants...... 116

Polymerization ...... 116 Hydroxylation ...... 116

Hydrogenation ...... 117 Anti-oxidants ...... 117 Miscellaneous uses ...... 117 Printing inks and litho varnishes...... 117 Tin plate ...... : ...... 118 7 SECTION VI FISH OILS OF BRITISH COLUMBIA Pilchard oil ...... : ...... 125 Drying properties ...... 129

Polymerization ...... 130

By neat ...... 130

By blowing ...... 130

By sulphur and sulphur chloride ...... 130 By steam distillation ...... 130

Driers ...... 132

Pilchard oil paints ...... 132 Hydrogenation ...... 133 Commercial salmon oil ...... 135 Herring oil ...... 140 Grey fishli ver oil ...... 143 Miscellaneous fishand fish liver oils ...... 146 Eulachon...... 146 Black cod, ...... 147

Ling cod liver oil ...... 148

Rat fish " " ...... 148 Grey cod " " 148 Halibut " " 149

8 ACKNOWLEDGMENTS

The writers wish to express their thanks to the following firms and indi­ viduals who have furnished diagrams, cuts, and information regarding equipment, plants and processes ; the California Press Manufacturing Co., San Francisco, Cal. ; the DeLaval Pacific Co., San Francisco, Cal. ; C. Heim & Co., London, Eng. ; Robinson, Butler, Hemingway & Co. Inc., New York ; the Ernest Scott & Co. Ltd., London, Eng. ; the Sharples Specialty Co., San Francisco, Cal. ; and Wurster & Sanger Inc., Chicago, Ill. We also wish to thank the owners and managers of the many fish oil and fish meal plants and other industrial establish­ ments that we have visited, both in Canada and the United States, for their courtesy in showing us the details of their different processes. 'vVe are alsoindebt ed to H. R. Beard, N. M. Carter, F. Charnley, D. B. Finn, R. M. Winslow and others for helpful criticisms and many valuable suggestions regarding the preparation of the MSS. Thanks are also due to P. A. Sunderland for the preparation of the diagrams and to Miss R. Gillies for the typing of the MSS.

INTRODUCTION

Fats and oils are widely distributed throughout the animal and vegetable kingdoms where they usually form a reserve food supply. As such they possess a high calorific value, and therefore constitute a concentrated source of energy. In addition, they protect the organism against sudden temperature changes, water penetration and mechanical shock. In the vegetable kingdom fats* are synthesized from carbohydrates such as ' sugar and starch, which, in turn, are synthesized from carbon dioxide and water. This important and primary step is effectedby means of the green chlorophyll of the leaves, and the energy supplied by sunlight. Fats and oils stored in the animal body may be produced from fats contained in the diet or synthesized from the non-fatty materials eaten. In herbivorous animals, for example, the fats are generally produced by synthesis from the carbo­ hydrates (and proteins) while in carnivorous animals the fat in the food may also be a source of the body fat. Although fat is found in other parts of the body, that stored as a reserve food supply is deposited in the adipose tissue from which it may be drawn as occasion requires. An animal usually deposits fat only when the food eaten exceeds the amount utilized by the body for energy requirements. The nature of the de-

*The word "fat" is sometimes used in a generic sense to indicate both solid and liquid fats. In general descriptions where the subject matter applies to both, the word "fat" will be used. 9 posited fat depends to a certain extent on the nature of,the food eaten. By changing the diet of an animal the nature of the deposited fat can be changed. Corn-fed hogs, for example, produce soft lards due to the high oil content of the diet. Similarly, cattle fed on an oil-cake diet yield softer tallows than those fed on a grass (carbohydrate diet). The animal body has the ability to modify ingested fats before depositing them in the adipose tissue. When the energy content of the diet is in excess of that required by the animal (i.e. when it is not active) and the diet also contains an excess oj jat, the fat deposited in the body will closely resemble that ingested. On the other hand, an active animal, fed on a balanced diet, will produce a body fat typical to the species, no matter what character of fat is ingested. Since diet and life habits have a profound effect on the nature of the de­ posited fats, animals, broadly speaking, tend to form specific fats or oils only in so far as their diets and habits are specific. Since, however, any species lives on a more or less characteristic diet, the fats formed are, within certain limits, generally characteristic of that species. Thus tallows from cattle and sheep are similar in general nature irrespective of the country of origin, but differ slightly in composition and properties, due to differences in the diet. It is not known definitely whether fish synthesize fats and oils directly or obtain them from their food. Many marine algae, copepods and diatoms con­ stituting the basal diet of fish, contain relatively large amounts of oil similar in nature to that found in the fishthems elves. It is therefore possible that the fish derive at least a part of their oil from this source. On the other hand, the great difference in the oils from various species of fish suggests that even if fish do not actually synthesize fats and oils, they at least have the power. to modify the nature of the ingested fats before storing them. Fats and oils stored in fishes apparently serve principally as a reserve food supply. The salmon, before ascending a river to spawn, spends several months feeding and storing up oil reserves for its long and arduous journey. When migration begins the salmon ceases feeding and there is a gradual decrease in the oil content as the fish ascends the river until, after spawning, the "spent" fish is almost free of oil. The same phenomenon occurs in other species of fish, which are, in general, rich in fat before spawning, but very poor in fat after that period.

10 •

SECTION I

THE GENERAL CHEMISTRY OF THE FATS

The constituents of a fat, namely, fatty acids and glycerine, consist essen­ tially of carbon, hydrogen and oxygen, chemically united in different ways. Three fatty acid molecules unite with one glycerine molecule to form a trigly­ ceride, and mixtures of various triglycerides constitute natural fats. That, briefly, is the "family tree" of the fats and it will serve as a key to the following more detailed account. Atoms unite to form molecules through forces termed "chemical affinity". These forces can be likened to arms holding the atoms together. All atoms have not the same number of arms ; some have one arm, some two, three and so on, up to seven. The number of arms or chemical forces an atom possesses is sig­ nified by the term "valence", a univalent element possessing one arm, a divalent two, a trivalent element three, and so on. A univalent atom can unite with one other univalent atom while a divalent atom can unite with either one other divalent atom or two univalent atoms. The principal thing to remember is that none of these "primary valence" arms can be left unsatisfied ; they all must be linked up with the arms of other atoms. Fats, as mentioned above, consist essentially of carbon, hydrogen, and oxygen, of which carbon is tefravalent (-C -) , hydrogen monovalent (H-) , and I oxygen divalent (0 =) . Carbon atoms have the important property of being able to unite with each other to form long chains, as, for example I I I I I I I -C-C-C-C-C-C-C-* I I I I I I I These chains constitute the "backbone" of the fatty acids. It will be noticed that the carbon atoms other than the two at the end of the chain have two of their four bonds united to other carbon atoms, thus forming the chain. In the fatty acids, . the other two borids of these carbon atoms are united to two hydrogen atoms. At the end of the chain is the acidic group, called the "carboxyl" group. This contains the oxygen of the fatty acid. A fatty acid as described is repre­ sented as follows : H H H H H H H H H H H H H H H H H Ot I I I I I I I I I I I I I I I I I / H - C- C- C- c- c- c- c- c- c- c- c- c- c- c- c- c- c- c I I I I I I I I I I I I I I I I I '" H H H H H H H H H H H H H H H H H OH Stearic Acid

*The valence arms uniting the carbon atoms are represented in the illustration as linked together and therefore shown as one bond. tThese formulae are usually written in a more condensed form . Stearic acid can be written CJ7HssCOOH or as CHs.CH2.CH2.CH2.CH,.CH2.CH2.CH2.CH2.CH2.CH2.CH2.CH2.CH2.CH2.CH2• CH2.COOH, or even CH3.(CH2)n.COOH, where n=1 6.

13 This represents a molecule of a fatty acid known as stearic acid. The hydrogen attached to the oxygen is easily replaceable by metals, a property which characterizes the "acid" nature of the compound. This is true of all acids whether organic or inorganic. When neutralized with an alkali, the metal of the alkali replaces this "acidic" hydrogen to form a salt, and water, thus :

HHH HHH 0 H H H H H H o I I I I I I / I I I I I I / H-C-C-C-C-C-C-C + Na-O-H --+ H-C-C-C-C-C-C-C +H-O-H

I I I I I I � I I I I I I � HHH HHH OH H H H H H ONa H

Organic acid + Lye --+ Sodium salt of organic acid + Water (sodium hydroxide) (soap)

H-Cl + Na-O-H Na-C! + H-O-H

Inorganic acid + Lye --+ Salt + Water (hydrochloric acid) (sodium chloride)

The salts of the fatty acids are usually known as soaps. The potassium and sodium salts of the naturally-occurring fatty acids comprise the soaps of commerce.

Besides reacting with alkalies to form soaps, fatty acids may unite with the hydroxyl group of alcohols to form "esters". If the alcohol has only one such hydroxyl (i.e. - CH2 - OH) it can react with only one fatty acid thus : CH3.CH2.OH + HO.OC.CH, CH3.CH,.O.OC.CH, + H20 ::=': Ethyl Acetic An ester + + Water alcohol acid � (ethyl acetate)

But some alcohols contain more than one of these groups. Glycerine, for exam­ ple, is an alcohol with 3 hydroxyl groups. Therefore one glycerine molecule can react with 3 molecules of fatty acids.

CH,Ol-I HO.OC. (CH2)n.CH3 CH2.O.OC.(CH2)nCH3 I I CHOH + HO.OC.(CH2)n.CH3 CH.O.OC.(CH2)nCH3 3H20 + I I CH20H HO.OC.(CH')n.CH, CH2.O.OC(CH2)nCH3

3 molecules A triglyceride Glycerine + -+ + Water fatty acid or fat

(n represents any number from 1 to 20) Naturally occurring fats and oils are complex mixtures of such triglycerides of fatty acids. In the above reaction it will be noticed that the arrows point in both

14 directions. This means that the reaction can be reversed, that is, by acting with water on the triglyceride it is decomposed into free fatty acids and glycerine. This reverse action is accelerated by the use of small amounts of inorganic acids such as hydrochloric acid, and also by alkalies. When alkalies are used, the alkali soaps of the fatty acids are obtained, as follows :

CH2.O.OC(CH')nCH, NaOH CH20H Na.O.OC(CH2)nCH3 I I CH.O.OC(CH')nCH3 NaOH -+ CHOH Na.O.OC.(CH2)nCH3 + + I I CH2.O.OC(CH')nCH3 NaOH CH20H Na.O.OC.(CH')nCH3

1 glycerine molecules -+ 1 molecule molecules sodium 3 + 3 molecule + lye glycerine soap of fatty acids Such a splitting up of the glyceride is known as hydrolysis or saponification. In the formula for the fatty acid given above each carbon atom had each of its four bonds engaged. In some cases, however, the carbon atom bonds may not be fully "satisfied" . They are then said to be "unsaturated". Such un­ saturation occurs between pairs of carbon atoms, and is represented by drawing two lines between the carbon atoms concerned, thus : I I -C-C- -c=c- ! I I I Saturated bond Unsaturated bond* The double bond does not mean a union of twice the strength of a single bond but rather that each carbon atom concerned can take up one more univalent atom. A double bond can therefore take up two atoms of hydrogen, two of chlorine, iodine, bromine or other monovalent atoms, but only one of oxygen since the latter is divalent. This is shown as follows: H H I I + -c=c- 2H - -C-C- + I I I I CI CI I I -c=c- 2CI --+ -C-C- + I I I I

o /� -C=C- -C-C- + o --+ I *The following terms are synonymous: double bond or linkage; unsaturated bond or linkage; ethenoid bond or linkage; ethylene bond or linkage; ethylenic bond or linkage. 15 All elements do not react with the double bond with the same ease; Hydro­ gen will react only in the presence of chemical activators (catalysts). Chlorine, bromine and iodine, on the other hand, react very energetically without catalysts. Bromine and iodine can be made to react quantitatively with unsaturated oils and therefore this reaction constitutes a valuable means of measuring the amount of unsaturation. The unsaturation of an oil is usually signified by its "iodine number" which represents the percentage of iodine absorbed by the oil. Oxygen also readily attacks the double bond as shown above. Fatty acids containing from one to six double bonds in their molecules occur in natural fats and oils, and consequently the oxygen of the air will readily attack such acids. Continued oxidation may eventually cause the molecule to split at the unsatur­ ated bond. We are now in a position to consider the naturally occurring fatty acids. From the foregoing, it is evident that there are two general classes of fatty acids, saturated and unsaturated. The unsaturated fatty acids may be further sub­ divided acoording to degree of unsaturation. Some fatty acids may have only one double bond, some two, three, and so on, up to six. Fatty acids differ also in the number of carbon atoms they contain. Natural fats contain fatty acids with a carbon content rangi)1g from 4 to 24 atoms. Fatty acids with the same number of carbon atoms but differing in the number of unsaturated (or ethylenic) bonds are said to belong to the same carbon series. Thus in the CIS series (fatty acids with 18 carbon atoms in their molecules) there are known the fully saturated acid (stearic) , the mono-, di-, tri-, and tetra-ethylenic acids, that is, acids with one, two, three and four double bonds respectively. In the following list a few of the simpler naturally occurring fatty acids are given. I.-Some naturally occurring fatty acids TABLE Acid Formula Common source Appearance

Lauric . C,2H,,02 . Coconut oil . Wh ite soft solid Myristic .... C'4H2S0Z . Palm kernel . \Vhite solid, quite hard Palmitoleic . C"H"O, . Whale oil . Liquid Palmitic . CJOH3202 . Tallow . \Nh ite hard solid Stearic .. .C,SH360, Tallow . White hard solid Oleic . . .. C,sH340, . . Olive oil. Colourless liquid Linolic . C16H3202 . . Linseed oil . . Colourless liquid Linolenic . C,sH300, . Li nseed oil . . . Co lourless liquid Clupanodonic . ...C"H'40, . Fish oils...... Colourless liquid

As the number of carbon atoms increases, the solubility of the a cids decreases and the acid character diminishes. At the same time the respective melting points and boiling points increase. The fatty acids occurring in natural fats and oils are insoluble in water and because of this do not have the sour taste characteristic of strong acids. It will be noticed from the above table that the unsaturated acids are liquid while the saturated members of the same series are solid, i.e. oleic, linolic and linolenic acids are liquid, whereas stearic acid is solid. 16 Increasing imsaturation therefore changes the physical as well as the chem­ ical properties. This is shown by the solidifying points of the acids of the CiS senes: Stearic acid (saturated) ...... 710C. (160°F.) Oleic acid (1 double bond) ...... 14°C. (157°F.) Linolic acid (2 double bonds) ...... -18°C. (_4°F.) Linolenic acid (3 double bonds) ...... -30°C. (-22°F.) In general, therefore, an increase in the number of carbon atoms in a fatty acid tends to raise the melting point and lower the solubility while an increase in the number of double bonds lowers the melting point and increases the solubility. The formation of simple triglycerides from 3 molecules of a fatty acid and one of glycerine has already been mentioned. It will now be realized that a great variety of simple glycerides is possible owing to the large number of differentfatt y acids. This number becomes still greater since mixed glycerides may also be formed. This is shown in the following diagram where the possible combinations of three acids with glycerine are represented ; and stand for the non­ Rl, R2, Ra acid parts of each of the different fatty acids. /0.OCR! /0.OCR! /0.OCR1 C,H. 0. OCR! CaH. 0. OCR2 C,Hs 0.OCR, '" '" 0. OCR! 0.OCR! '"O.OCR! /O.OCR, /0.OCR2 /0.OCR1 C,H. " 0.OCR, C,H. " OCR! C,Hs 0.OCR, '" "0.OCR2 "0.OCR20. 0.OCR2 /0.OCR1 /O.OCR, /O.OCR, /O.OCR, C,Hs '" OCR, C,H. "" 0.OCR, C,H. " 0.OCR1 C,H. '" OCR, O.OCR,0. O.OCR, "O.OCR, O.OCR,0.

Possible arrangement of fatty acids in glycerides FIGURE 1. s Each of the glycerides shown above has its own peculiar properties such as melting point, solubility, etc. Furthermore, the relative posit'ion of the fatty acids in the molecule has an effect on the properties of the glyceride. For exam­ ple, glyceride 1 (below) will have properties slightly different from glyceride 2, although the composition is the same. /0.OCR1 /O.OCR! C,H. 0. OCR, C,H. 0.OCR! " ",O.OCR, 0.OCR2 1 2 Isomeric glycerides FIGURE 2. I t is evident then that the number of different mixed glycerides obtainable from relatively few fatty acids is very great. In natural fats and oils, simple glycerides are scarce, by far the larger number being mixed glycerides. Fats and oils are complex mixtures of various glycerides, these glycerides being mutually soluble in each other. The chemical characteristics of the fatty acids are exhibited to a great extent

17 2 by the fats in which they occur. A fat which has a preponderance of unsaturated liquid acids will be a liquid but if the chief acids are saturated, it will be solid. The generic name "fat" includes both liquid and solid fats but in industrial par­ lance a fat is a substance which is solid at ordinary temperatures and an oil, one that is liquid. This classification is evidently an arbitrary one as is shown in the case of coconut oil which may be an oil in summer and a fat in winter. (See foot­ note to page 9.) The double bonds react in much the same manner whether the fatty acid is free or combined as a glyceride. Thus, unsaturated oils will absorb oxygen, chlorine, bromine and iodine as do the component acids when in the free state.

SUMMARY FATTY ACIDS: They are composed of carbon, oxygen, and hydrogen. They are weak acids which may be neutralized by alkalies to form salts (soaps) and water. They unite with glycerine to form tri-glycerides. They may be saturated or unsaturated. Increasing carbon content decreases solubility and acidity but raises melting point. Increasing un saturation increases solubility and lowers melting point. Unsaturated bond reacts with oxygen, chlorine, bromine and iodine readily and with hydrogen under special conditions. The more highly unsaturated the acid, the greater its tendency to oxidize.

GLYCERIDES; They are neutral substances. They consist of glycerine combined with 3 molecules of fatty acids. They may be hydrolyzed to free fatty acids and glycerine. They may be simple or mixed, the latter preponderating in natural fats. They are the chief components of fats and oils. The behaviour of double bond similar to that in fatty acids.

REFERENCES

ALSBERG, C. L. AND A. A. TAYLOR. The fats and oils. Stanford l�niversity Press, California. 1928. ARMSTRONG, E. F. AND J. ALLEN. The fats. J. Soc. Chem. Ind. 43. 207T. 1924. HILDITCH, T. P. The industrial chemistry of fats and ·waxes. Van Nostrand & Co., New York. 1927. HOLLEMAN, A. F. A text-book of organic chemistry. John 'Wiley & Sons, New York. 1925. LEWKOWITSCH, G. and G. H. WARBURTON. Chemical technology and analysis of oils, fats and waxes, vol. 1. Macmillan & Co. 1921. 18 SECTION II

THE PROPERTIES OF FATS AND OILS

OXIDATION

In the preceding section it is shown how substances with an unsaturated bond may become saturated by the addition of hydrogen, oxygen and other elements. Unsaturated oils will not readily take up hydrogen except with the aid of a metallic catalyst under special conditions but they will all absorb oxygen. The more highly unsaturated the oil the more readily it will oxidize. It has also been pointed out (cf. page 15) that the iodine absorption is an index of the degree of un saturation ; the higher the iodine value the greater the unsaturation. The iodine values of a few common oils are given in table II.

II.-The unsaturat ion of oils as shown by their iodine value TABLE

Fat or oil Io dine value range

Coconut oil ...... 7- 11

Cacao butter ...... 32- 41

Mutton tallow ...... 35- 46

Beef tallow ...... 38- 46

Lard ...... 46- 70

Olive oil ...... 79- 88

Peanut oil ...... 83-100 Corn oil ...... 111-130

Shark-l iver, Grey-fish liver, etc ...... 110-135

Soya bean oil ...... , .... . 119-135

Whale oil...... 121-146

Polar bear fat .. .. : ...... -147 Seal oil ...... 127-141 Po rpoise blubber oil ...... 90-100 Salmon body oil...... 125-1 65

Herring oil ...... 123-142

Menhaden oil...... 139-173

Chinawood oil ...... 160-180 Pilchard oil ...... 176-186

Linseed oil ...... 173-185

The first six oils in this list, because of their low degree of unsaturation, do not readily absorb oxygen from the air. They are classed as non-drying fats or oils, and are relatively stable. The next few in the group absorb oxygen slowly but do not give a solid film. They become viscous and sticky and acquire an acrid odour. These oils are known as semi-drying oils. The drying-oil group' includes those oils that readily absorb oxygen and form tough elasticiiltns. f i China wood oil and linseed oil are the best known of the vegetable oils o th s 21 class while some of the fishoils such as menhaden and pilchard are also included in this group. The drying oils are used to a great extent in the paint and varnish industry and it is this property of oxidizing to form tough elastic filmsthat makes them so valuable. The rate of oxygen absorption can be greatly increased by means of catalysts known as "driers". These are usually compounds of lead, manganese and cobalt. The effectof these driers is shown graphically in figure3. I t can be seen that the oil A which contains no drier absorbs oxygen very slowly at first; afterwards the absorption takes place more rapidly. The period of relatively slow absorption is known as the "inductive period". On the other hand, the oil B which contains a metallic drier begins to absorb oxygen almost as soon as it is exposed to the air, the inductive period being extremely short. It will be noticed that the oil A absorbs o�ygen very rapidly once the inductive period has been passed. This is due to an accumulation of oxidized products (organic peroxides, see footnote*) in small amounts during the latent period. These act as catalysts in a manner similar to that of the metallic driers. This type of reaction, in which the substance manufactures its own accelerator, is known as "autocatalytic", or self-assisting. It will be understood, then, how the absorption becomes faster and faster since more of these catalytic substances are formed as the reaction proceeds. A balance is eventually reached between the amount being formed and the amount being used up to oxidize the unchanged oil. The rate then becomes constant until the oil approaches saturation, when the oxygen absorption gradually slows up. While the exact mechanism of the action of the oxidizing catalysts is not completely understood, these substances all act more or less in a similar way in that they can take up oxygen themselves by a loose type of linkage and hand it on to the substance undergoing oxidation.

*\Vhen the unsaturated bonds in the fatty acids of oils are oxidized, either one or two atoms of oxygen may be added, according to conditions of temperature, etc. The products are known as oxides and peroxides, respectively. The reactions may be represented as follows:

I I -c -C", ° --+ I/0 -CII + -C I I Oxide. I -CI -C--OI -C",

-+ I/0 ° -CII + 2° --+ -C-OI I -C + I I I Peroxide.

The peroxides are less stable than the oxides, breaking up to oxides and liberating free oxygen which may then oxidize another unsaturated bond.

22 ANTI-OXIDANTS

The catalysts so far described have been of the type that promote or accel­ erate reactions. However, there are many substances, known as "anti-catalysts", that have the opposite effect, that is, they retard chemical reactions. Substances that retard the action of oxygen are known as "anti-oxidants". Many of these are effective in preventing or at least hindering the oxidation of oils and fats. Amongst the most efficientof these are hydroquinone, pyrogallol, phenol, thymol, resorcinal and naphthol. As a rule anti-oxidants retard oxidation to a degree proportional to the con­ , centration. Equal amounts of each, however, do not have the same effect, for some are more active than others. The effect of 0.05 per cent. hydroquinone

B

A-Raw Oil 8-0il wifh Drier

FIGURE Oxygen absorption. 3.

and pyrogallol in retarding the oxygen uptake of pilchard oil is shown graphically in figure 4. For purposes of comparison the oxygen uptake of a sample of the raw oil and one containing 0.05 per cent. of cobalt-oxide drier are also given. Curve 1 (figure 4) represents the rate of oxygen absorption of pilchard oil alone; curves 2, 3 and 4 represent the absorption when cobalt drier, hydro­ quinone and pyrogallol, respectively, are added. It will be noticed that the raw­ oil curve is S-shaped ; this is typical of an auto-catalytic reaction. The cobalt drier, as mentioned previously, eliminates the period of induction, the oxygen absorption commencing immediately on exposure to the air. Hydroquinone and pyrogallol have a marked retarding influence on the rate of absorption, the latter substance being the mor:eeffective at the same concentration. By increasing the' 23 concentration, the oxygen uptake can be stopped entirely, at least for a certain period, after which the absorption 'willagain proceed. If subjected to high temperatures and high concentrations of oxygen the protective period afforded by the anti-catalyst is reduced. It appears that in preventing an oil from oxidizing, an anti-catalyst itself gradually becomes oxi­ dized. The degree and period of inhibition depends, therefore, not only on the nature of the oil and anti-catalyst but also on external conditions. On this account no general statement can be made regarding the use of anti-oxidants in industrial oils. vVhen considering the uses of fish oils it will be indicated 'where these substances may possibly be used.

b. ,

70 "....

5 2V ....- · II / : 5 V

· I 1/ ! 45 I · I V � f 5 II / ....- · � ....-3....- if IV l/ I V I-: l/ - : I / V 4 fo- f - I ,� V .,...... � i II ...,:� � , i "1 g 12 16 20 N .ell -'2 36 .fb 4-1 48 52 5", 00 64 68 7Z. -,0 80 (/.:; fiB 9ie! 96

Time '11 Hours

FIGlJRE 4. Effect of driers and antioxidants on 0, absorption.

ACTION OF LIGHT

Light is an active agent in effecting certain changes in fats and oils. Years ago artists used to prepare their own oils by exposing them to the air and sunlight for long periods. During this treatment the oils became almost colourless and increased considerably in viscosity. The action of light on oils has been utilized industrially chiefly for its bleaching action. The colouring matter in naturally occurring oils is very easily oxidized and light appears to aid this oxidation. The thickening of oil is known as "polymerization". It is brought about by the re­ action of one double bond \vith another. This subject will be considered in a later section.

24 HYDROLYSIS OR SAPONIFICATION

The process of splitting oils or fats into their component parts, glycerine and fatty acids, has already been mentioned. The reaction can be brought about by mineral acids and alkalies, or by steam under pressure. \Nhen acids are used, glycerine and the free fatty acids are obtained but unless special precautions are taken, the fatty acids become discoloured and are then of inferior value for indus­ trial purposes. The alkali process is commonly used in the soap industry. The hydrolysis or saponification of oils and fats by moisture at normal tem­ peratures is a very slow process. It may be hastened to a small extent by light but much more so by the presence of naturally occurring catalysts called "e'1zy­ mes". The particular enzymes that promote the hydrolysis of fats and oils are known as "lipases". They are of great importance in fat and oil technology. Lipases occur in the living organism and their function is to split up the oils and fats into their component parts prior to assimilation. The chief sources of these fat-splitting substances are the seeds of plants, the liver, and digestive organs of animals. They act on oils and fat at ordinary temperatures and their activity increases up to a certain optimum. Lipases from various sources have different optimal temperatures but they are all destroyed at 100°C. (212°F.). If the raw materials used for the production of oils contain lipases, care must be taken that their activity is destroyed, otherwise they may contaminate the finished oil and bring about a rapid increase in the free acidity. Artificial fat-splitting catalysts have been invented and several find use in industry. The best known of these is "Tvvitchell's reagent", used to some extent in the manufacture of soap. It consists of a sulphonated aromatic compound made from oleic acid, naphthalene and sulphuric acid. One-half to one per cent. is sufl1cient to effect hydrolysis, which is carried out with open steam at a tem- erature of 100°C. The reaction takes from 12 to 24 hours for completion.

RANCIDITY

The preceding paragraphs have indicated that oils are not stable but may undergo a variety of chemical changes. Some of these changes produce decom­ position products which may be detected by the sense of smell or taste even \\'hen present in extremely small amounts. \\Then such products develop, the oil is said to be "rancid". Rancidity is brought about by two general processes, chemical and biological. Chief among the former are the oxidation of the unsaturated bond, and the hydrolysis of the oil to glycerine and free fatty acids. The oxidative type of deterioration follows a course similar to that of the oxidation of drying oils. In order that oxidative rancidity may take place throughout the entire bulk of an oil or fat, the oxygen must be dissolved or mech­ ani cally entrapped. On exposure to air, traces of oxygen may become dissolved in amounts sufficient to cause rancidity even if the oil is subsequently stored away from air. The period of induction is very important since it represents the length of time an oil will keep before oxidation becomes noticeable. However, long

25 before the oil has reached the very active stage in the oxidative process, the pre­ sence of the decomposition products can be detected by the taste or smell. Once they have been formed, no matter how small the amount, they speed up the reaction until the material is extensively oxidized. The speed of oxidation is affected by heat, light, acidity and metallic cata­ lysts, as pointed out previously, and since the smallest traces of oxidation products are of importance in bringing about a rancid condition these agents take on a greater significance. With the increase of every ten degrees centigrade, the speed of a chemical reaction is accelerated from two to three times. Oils and fats intenc:ied for food or other special purposes should therefore always be stored at as Iow a temperature as possible. Light shortens the inductive period to a marked degree. Metallic catalysts, however, are much more active promoters of oxida­ tion. Remembering that traces of rancidity are most important in the case of edible oils and fats and that the slightest degree of oxidation can render these unpalatable, it will be realized that most minute traces of metallic catalysts can do considerable harm. The metals most active in this respect are iron and copper. Small amounts of these may become dissolved by the oils when they are processed in apparatus of these JJ}aterials. It is reported (Davies 1930) that from 0.8 to 10 parts per million of iron and copper definitely accelerate oxidative rancidity of edible fats. Another type of chemical reaction associated with rancidity is hydrolysis of the neutral fat or oil to glycerine and free fatty acids. The taste associated with this kind of deterioration is quite different from that associated with the oxidative type. Hydrolysis is brought about by traces of water remaining in the fat and also by too high a temperature of storage. Since the free fatty acids tend to speed up oxidation, it is evident that when hydrolysis occurs the oil becomes more susceptible to oxidative rancidity. However, since hydrolysis is relatively slow, an oil or fat which has been contaminated by traces of metals or exposed to light, may develop the oxidative type of rancidity without perceptible increase in the acid value.

BACTERIA AND MOULDS

Certain bacteria and moulds may also cause deterioration of fats by means of the enzymes they secrete. A few common bacteria produce lipases which split fats into glycerine and free fatty acids. Other bacteria (zymogenic) may then act on the free fatty acids, breaking them down to carbon dioxide and water. Certain bacteria which decompose proteins may also cause deterioration of fats. An oil or fat containing finelydivided particles of protein matter is susceptible to this type of rancidity since these particles form a very good nutritive medium for proteolytic bacteria. The products of the metabolism of these organisms are soluble in oil and usually have a very foul odour. These three types of bacteria mentioned may all act at the same time ; con­ sequently an oil under these conditions rapidly develops a high acidity and a dis­ agreeable odour. The free acidity can be removed easily by subsequent refining

26 but it is difficult to remove the odour, even by drastic treatment. It will there­ fore be realized that the keeping qualities of an oil or fat are to a large extent dependent upon its freedom from impurities. :'Ioulds cause more deterioration in fats and oils than bacteria. This is probably due to the fact that many of the former secrete fat-splitting enzymes. Moulds may be classified (according to the products formed) , as "ketone" and "acid" types. The firsttype of mould attacks only fats that contain fatty acids of low molecular weight since the fatty acids of high molecular weight are toxic to them. Coconut oil, butter and similar fats are very readily acted on by this type. The acid-forming moulds produce large quantities of lipase which liberate free fatty acids. These may then be oxidized by other enzymes (i.e. oxidases and peroxidases) present in the moulds forming fatty acids of lower melting point. The fatty acids liberated do not poison these moulds or prevent their growth. Consequently, this type is more apt to cause deterioration of oils than is the ketone type. In the production of both fish-liver and fish-body oils there is ample oppor­ tunity for contamination by lipase- and moisture-containing protein matter. In the manufacture of cod-liver oil great care has to be taken that the expressed oil is immediately freed from minute particles of liver material. Lund (1925) has claimed that cod-liver oil stored in contact with pieces of the liver keeps fresh for a longer period. This, Lund says, is due to the presence of substances in the liver that inhibit oxidation of the oil by absorbing the oxygen. Such a practice is not to be recommended, however, since the liver material forms a very good food for proteolytic bacteria. In the manufacture of fish-body oils for industrial usage every effort should be made to keep the equipment clean. The liquid mixture coming from the presses contains water, oil and dissolved protein matter, in the form of an emul­ sion. This, as already pointed out, is an excellent medium for bacterial growth. Consequently the oil rapidly develops a high acid number (high free fatty acid content) and a disgusting odour. As the protein matter decomposes, the emul­ sion breaks and the oil separates. It is obvious that the oil produced under such conditions is of inferior quality. Recognizing this fact, oil technologists usually separate the oil from the emulsion by special means. Furthermore, the keeping quality of the oil is greatly influenced by the cleanliness of the storage tanks. A "fermenting" emulsion usually deposits a coating of highly acid oxidized oil on the sides of the tank and the decomposing protein leaves a slime on the bottom. If these are allowed to accumulate they will contaminate any oil stored in the tanks and thus hasten the onset of rancidity. Frequent cleaning of tanks is therefore necessary in the production of first-class oils. POLYMERIZATION When fatty oils are heated they gradually become more viscous, and if heated a suitable temperature they may finally form a gel or jelly-like mass. to In the industry, this process is known as "bodying" and is much used in the pre-

27 paration of oils for use in varnishes and allied products. This phenomenon is the result of a chemical change knmvn as "polymerization", which is brought about by the linking up of unsaturated molecules at the double bond. It will be recalled that a "double bond" signifiestwo mutually bound carbon atoms each of which has a free valence bond temporarily united to the adjoining

HI H I H I H, H I H I .. · - O-O-O= C-C-C -··· I H H H H

HI H I H H - - - - .. ' 0 0 0==:0, 0-0-··· H H H H H H

Tw o unsaturated Bonds in acfjacent l'1o/ecules.

HI H H HI H H

- ...-C- I C-C I O-O-I O-' I " H H I I H H

� � � � · "------'" 0I 0 I 0 I 0f I 0 I 0I H H H H H H

iJn saturated Bon ds op "ned up (a ctivatecl)hy He at.

H H H H H H I I I I

· .. - -- - -0-0, 0 0-0I 0-'"I H H H H

H H HI HI

· .. - - - - 0-0-0 0 0I 0-'I "

H H H H H H

a Activated Do uble 80nds react to fo rm 4-Atom. COlnpounJ. FIGURE 5. Polymerization of unsaturated bonds.

carbon atom. 'When the compound is heated this extra bond is opened and the two double bonds may react to form a ring compound as shown in figure 5. Thus, in polymerization, unsaturated bonds become saturated by mutual inter­ action when they are activated by an agency such as heat, light, or chemical catalysts.

28 If the t,yO reacting unsaturated bonds are in the same glyceride molecule, the reaction is known as "intramolecular" ; if in different glycerides, it is called "intermolecular". The two types of polymerization, intra and intermolecular, are shuwn in a graphic form in figure 6. It will be recalled that each glyceride molecule contains three molecules of fatty acids. If these three acids are unsaturated, both intra-molecular and inter­ molecular reactions may take place. If the fatty acids have more than one double bond, one bond may react with one unsaturated bond within the same glyceride and the other with an unsaturated bond in another glyceride molecule. Consequently, big unwieldly molecules are formed. As they grow in size, their mobility decreases, until, after a certain complexity is reached, they are immobile and have a definite gel-structure. It is clear that as the number of unsaturated bonds in the fatty acids increases, the possibility of the formation of complex molecules also increases. It must also be realized that this representation can only be shown in two dimensions on paper, but it actually has three.

II

II

in termolecular Po(ymerization

FIGURE 6. Polymerization of glycerides.

In a fatty oil there may be unsaturated fatty acids containing from one to six double bonds. The ease with which these acids polymerize depends upon the relative positions of the double bonds and also upon the number present. In general, the more highly unsaturated an oil, the more easily it will polymerize. Fish oils are highly unsaturated and it is therefore of interest, at this point, to examine their behaviour when subjected to heat treatment. The following graph (figure 7) shows the changes that occur when British Columbia pilchard oil, cleared of stearine at 6°e. (42.8°F.), is heated in a vacuum. In the graph the iodine values and viscosities are plotted against the time of heating for two series of experiments, the firstcarried out at 200°e. (392°F.), and the second at 250°e. (482°F.). At 200°e. the iodine value falls gradually and uniformly from 190 to 170 during the 24 hours. At 250°e., however, the type of curve obtained is entirely different. The fall in iodine values is rapid for the first 29 6 hours and then gradually decreases until the 24th hour. The total decrease in iodine value in this case is 80 units. The viscosity of the sample polymerized at 200°C. changes very little during the 24-hour period. At 250°C., however, thickening starts immediately and increases during the whole period. On prolonged heating the sample sets to a gel. These experiments seem to indicate that there is probably a critical temperature above which polymerization takes place readily but below which practically no change occurs.

16 190

� 14 � I 180 I I ...... I r--- " � 170 12 �/ I

I I / , I , 180

I , to I , ,V " o / � rt>/ \ I � 150 � I , ,/ t: I / ,/ �0 I I -.. , 140 , , I , \ I _Iodine Va lues o. ____ ("> ,/ Vis cosity - " 130 �X ,/// 2. , 120 , , " � /' /:------?£'?..q�� ------� o � 110 12 /6 20 Z4 Time in Ho urs FIGURE 7. Polymerization of pilchard oi l in vacuo.

Although the degree of unsaturation is greatly diminished by bodying oils, it has been found that they will take up oxygen, though at a slower rate. It is possible that oxygen breaks up the ring formation, thus allowing oxidation to proceed as in the raw oil. -While the exact mechanism of polymerization and oxidation is as yet by no means clear, recent research work has done much to indicate the general process.

30 As previously stated, the molecules must be activated by heat before poly­ merization can take place. Other means may be used to bring about this activa­ tion ; one of the most powerful is light, particularly ultra-violet. Oils subjected to this treatment become viscous and much paler in colour than those polymerized by heat. The process, however, takes a longer time and is very costly. It has not yet been established that the changes occurring in the two cases are the same. Recently several patents have been taken out on the use of catalysts for the polymerization of oils. The most effective of these is benzidine, an aromatic amine. So far, however, no extended commercial use has been made of these catalysts for the polymerization of fishoils.

HYDROGENATION In a previous section it was pointed out that the difference between an un­ saturated liquid oil and a solid saturated fat (of the same carbon content) was that the latter had its full quota of hydrogen. If an unsaturated oil can be made to take up hydrogen to fully satisfy the unsaturated bonds in its glycerides it \vill be converted into a hard fat, since glycerides composed of the fully saturated fatty acids are solid. The addition of hydrogen to oleic acid to form stearic acid is shown in figure 8. Thus, if an oil like olive oil, which contains a large amount of oleic acid, is made to take up the remainder of its amount of hydrogen, it, too, will be changed into a solid fat. While this reaction appears to be very simple, consisting solely in the addition of hydrogen to the double bond, the bubbling of hydrogen through an unsaturated oil has no effect; the hydrogen merely passes off. Even at high temperatures and pressures hydrogen will not act on unsaturated oils. It was not until the famous French chemist, Sabatier, made his discoveries regarding catalysts that the hardening of liquid oils through hydrogenation became possible. Catalysts have been mentioned in a previous section as substances that modify the velocity of chemical reactions without being permanently affected themselves (chemically) . The catalysts that bring about the addition of hydrogen to unsaturated sub­ stances are chiefly compoundsof platinum, palladium and nickel. Nickel is used almost exclusively in the industrial application of this process. In brief, the hydrogenation process is as follows. An absorbent earth, such as Fuller's earth, is treated with a strong solution of a nickel salt and then mixed with an alkaline solution. Nickel hydroxide is thus precipitated on the surface of the Fuller's earth. The material is then dried and "activated" by treatment with hydrogen at temperatures between 300 and 450°C. (572 and 842°F.) until a part of the nickel is reduced to the metallic state. This activation may take place in the dry state or mixed in a small amount of oil. After activation the catalyst is mixed with the oil to be hardened, and the mixture treated with hydrogen at a temperature between 175 and 200°C. (347 and 392°F.). Hydrogen is then passed into the mixture and is rapidly absorbed. While the mixture is still hot, the catalyst is removed by means of filter presses 31 and the filtered oil, on cooling, sets to a solid fat. Some processes use higher pressures and lower temperatures. A typical hydrogenating plant will be de­ scribed in a later section.

H H I H-C-H H-C-H I I H-C-H H-C-H i H-C-H H-C-H I H-C-H H-C-H I H-C-H H-C-H I I H-C-H H-C-H

I H-C-H H-C-H i H-C-H H-C-H ! I H-C H-C-H

- II + I H-C H-C-H

I I H-C-H H-C-H

H-C-H H-C-H

H-C-H H-C-H I I H-C-H H-C -H

H-C-H H-C-H

H-C-H H-C-H

H-C-H H-C-H ! I H-C-OH H-C-OH II II o o FIGURE 8. Hydrogenation of oleic acid to stearic acid

When a fish oil is thus hardened by the addition of hydrogen it is changed into a different compound. Many of the properties also are changed. The colour is usually bleached white , characteristic odours are removed, and the solid fat is usually tasteless, since the highly unsaturated fatty acids to which the fishy odour and taste are due become saturated in the process.

32 The catalysts that bring about the addition of hydrogen to these unsaturated compounds are easily affected by certain substances that render them inactive. Some of these substanc.es occur naturally in raw oils. They may be partially removed by refining but a catalyst usually does not last very long in commercial practice and has to be continually reactivated. Some oils contain more of these interfering substances than others. The more important of these are : decom­ posed protein matter, sulphur compounds, free fatty acids, partially oxidized oils, and unsaponifiable matter. The better the quality of the raw oil the less refining it will require preliminary to hydrogenation.

SULPHONATION

Concentrated sulphuric acid reacts very energetically with unsaturated oils. The chief reaction takes place at the double bond where the sulphuric acid at­ taches itself, but a certain amount of hydrolysis takes place in which one or more fatty acids may be split from the glycerine and substituted by the sulphuricacid. The sulphonated* products when neutralized with ammonia in many cases give water-soluble oils. These so-called "soluble oils" are used to a great extent in the textile and tanning industries. The substance originally used as a raw material for the production of these soluble oils was castor oil, and the product was known as turkey-red oil, since it was first used in the dyeing process using turkey-red dye. Many other oils are now sulphonated but the products vary greatly with the oil used. The sulphonation process is fairly simple. The oil is agitated in a lead­ lined vessel, containing cooling coils, and concentrated sulphuric acid, to the amount of about 25 per cent. of the weight of the oil, is allowed to run in slowly. Since heat is evolved in this reaction, the temperature tends to rise but is kept *The two types of reaction may be shown by the following equations:

-CH =CH- + H2S04 - -CH-CH- + I I OH SOaH Unsaturated plus Sulphuric gives Sulphonated bond acid product This sulphonated product, however, is unstable in water. hydroxy compound is formed and A free sulphuric acid regenerated as follows: -CH-CH- + H20 -CH-CH. + I I --+ I OH SOaH OH Sulphonated plus Water gives Hydroxylated plus Sulphuric compound compound acid The second type of reaction in which a fatty acid in the glyceride is replaced by sulphuric acid can be represented as follows: CH•. COOR CH.COOR This type of sulphonated I I CH .COOR CH.COOR product is stable in the I I presence of water. CH2.COOR CH.OSO.H

33 3 down by the coils. The temperature at which the process is allowed to proceed depends upon the character of the oil treated. Castor oil may safely be treated at 35°C. (97°F.), but oils of a more unsaturated nature, such as linseed and fish oils, have to be treated at lower temperatures. vVhen all the acid has been run in and the mixture has cooled, the excess of sulphuric acid is removed by washing with water. The product is then dried and partially neutralized with soda or ammonia. The neutralization with these alkalies is carried just far enough to make the product soluble in water. The value of these sulphonated oils rests in their power of emulsification. Emulsions of oil and water produced by them will remain permanent for long periods of time. Sulphonated fish oils, when produced in the manner described above, do not always give completely water-soluble products but in general, they have great emulsifying powers. The particular properties and uses of these sulphonated fish oilswill be dealt with in later sections.

SULPHURATION

By sulphuration is meant the chemical addition of sulphur to an oil. In many ways sulphur reacts like oxygen. It forms many compounds similar to thoEe formed by oxygen and usually will react with those compounds with which oxygen reacts. Sulphur, however, does not act on oils in the cold and it is only after fairly high temperatures have been reached that it will attack unsaturated oils. Once the reaction has been started, it usually proceeds with considerable violence since heat is generated. If allowed to proceed without cooling, large amounts of hydrogen sulphide gases are formed and the mass stiffens and assumes an appearance like spongy rubber. If the temperature of the reacting materials is kept below 160°C. (320°F.), there is little, if any, gas formed and a viscous rubbery product is obtained. On ageing, the product loses its tensile strength and becomes "crumbly". Partially sulphurized oils have properties which make them of value as rubber substitutes for the waterproofing of various kinds of fabrics. REFERENCES

LEWKOWITSCH, J.,AND G. H. \VARBURTON. Chemical technology and analysis of oils, fats and waxes. Vol. II. London. 1922. :\TORRELL, R. S. AND H. R. VVOOD. The chemistry of the drying oils. New York. 1925. OXIDATION HILDITCH, T. P. AND J. J. SLEIGHTHOLME. Studies on the nature of an tioxygens present in natural fats. 1. Separation of fatty derivatives from anti­ oxygens by distillation. 1. Soc. Chem. Ind. 51, 39T. 1932. HOLM, G. E., G. R. GREENBANK AND E. F. DREYSHER. Susceptibility of fats to oxidation. Ind. Eng. Chem. 19, 156. 1927. MATTILL, H. A. AND B. CRAWFORD. Autoxidation of corn oil as related to its unsaponifiable constituents. Ind. Eng. Chem. 22, 341. 1930.

34 MOUREU, C. AND C. DUFRAISSE. Catalysis and autoxidation. Chem. Rev. Vol. III, No. 2 1926. POWICK, W. C. Compounds developed in rancid fats with observations on the mechanism of their formation, J. Agric. Res. 26, 323-62. C.A . 18, 1580. 1923. VIBRANS, C. Anti-oxidants in edible oil preservation. and Fat Ind. F. Oil 8, 223. 1931. RANCIDITY BARNICOAT, C. R. Rancidity changes and the flavour of fats. J. Soc. Chem. Ind. Vol. 50, 39, 361T. 1931. DAVIES, vV.L. Tests for the incipient rancidity of fats. J. Soc. Chem. Ind. 47, 185T. 1928. ENIERY, J. A. AND R. R. HE�LEY. Studies on rancidity. I. The influence of air, light and metals on the development of rancidity. Ind. Eng. Chem. 14 , 937. 1922. GRETTIE, D. P. AND R. C. NEWTON. Susceptibility of fats to oxidative rancidity. Oil and Fat Industries, 291. 1931. HUSA, vV.J. AND L. lVI. HUSA. Effectsof various compounds on rate of develop­ ment of rancidity in fats and oils. J. Soc. Chem. Ind., vol. 47, No. 19, 339. 1928. KERR, R. H. "The cause and prevention of rancidity". C.A . 15, 3404. 1921. LUND, A. The oxidation of cod-liver oil. Tids. Kemi. Berg. 5, 102, 1925. C.A . 19, 2366. 1925. POOL, W. O. Rancidity and stability in shortening products. Oil and Fat Indust. 331. 1931. POLYMERIZATION CUTTER, J. O. The polymerization of drying oils. J. Oil and Colour Chem. Assoc. 13, 66. 1930. ORRELL, R. S. Varnishes and their components. Oxford Technical Publica- ::VI tion, London. 1923. HYDROGENATION BOLTON, E. R. Recent advances in the hydrogenation of oils. J. Soc. Chem. Ind. v. 46, 444T. 1927. ELLIS, C. The hydrogenation of organic substances. Van Nostrand Co" New York. 1930. LUSH, E. J. Kinetics of hydrogenation. J. Soc. Chem. Ind., 43, P. 53T. 1924.

SULPHONATION LEWKOWITSCH, J. AND G. H. WARBURTON, lac. cit. "OMEGA". The sulphonated oil industry. Chem. Trade J. and Chem. Eng. 163. 1925.

SECTION III

COMPOSITION AND OCCURRENCE OF FATS AND OILS, WITH PARTICULAR REFERENCE TO FISH OILS

VEGETABLE FATS AND OILS

Fats and oils in plants occur chiefly in the reproductive structures such as the fruit and the seed. In the olive and palm, for example, the larger portion of the oil is contained in the fleshy pericarp surrounding the kernel. The kernel itself contains oil but usually of a different character. In the palm fruit, for instance, the pericarp yields a solid fat whereas the kernel yields an oil. In plants which do not bear fleshy fruits the oil occurs almost entirely in the seed, or distributed widely throughout the entire plant as in the cedar, spruce and pine. Fats or oils from the same or different species of plant may vary somewhat in composition with climatic conditions and soil fertility, but on the whole the variations are small. Thus linseed oils from various parts of the world,­ Canada, Argentine, the Baltic, India and Australia,-vary somewhat with regard to the proportion of the various fatty acids contained, but the variation is not of sufficient magnitude to affect the characteristic properties. As a rule, fats and oils of cooler climates are liquid and more highly unsatur­ ated than those of tropical regions. This may be seen from the iodine values of various fats and oils in the table on page 21. The relationship between unsatur­ ation and drying properties has already been pointed out, but will be seen more clearly from the composition of a few common fats and oils in table III.

TABLE IlI.-Composition of naturally occurring vegetable oils Semi- N on-drying oils drying Drying oils Cacao Palm Olive Cottonsee�1I Linseed China wo od butter oil oil oil oil oil ------Io dine Iodine Iodine Iodine Io dine Io dine values values values values values values Saturated acids 32-41 53-58 79-88 104-113 173-200 160-18 I o ------Myristic C14H2802 . ... 1.0 Trace Palmitic C16H3202 ... . 23 35 .5 7 23 .4 8.7 Stearic . ... C18H3602 . .. . 33 .6 8.5 2 Arachidic C2oH4002 ...... Trace I Behenic C22H4402 . . . Lignoceric C24H4802 .... '1. "

Unsaturated acids Oleic acid CSH3402 .. 41 .8 48 .0 85 23 .0 7.4 4.8 Linoleic acids ClsH3202 . .. 1.4 7.0 6 53 .4 62 .0 92 .6

Linolenic acids C1s ,0 ' . 24 .0 H 02 .. ,Ii 39 I t will be observed that the two drying oils-linseed and China wood-differ from the others in composition chiefly in containing a very large proportion of unsaturated fatty acids such as linoleic acid (2 double bonds) and linolenic acid (3 double bonds) which dry when exposed to the air. In linseed oil the propor­ tion of these acids is about 85 per cent. and in China wood oil, about 93 per cent. Cottonseed oil, on the contrary, contains only about 54 per cent. of drying com­ ponents ; hence its semi-drying character. Oils with still smaller amounts of drying fatty acids are practically non-drying. They never form a tough resinous film but merely thicken or become gummy and sticky even when exposed for very long periods. While the tendency of an oil to dry depends on the proportion of drying fatty acids it contains, the character of the dried film depends largely on the nature of the drying components. This, too, may be illustrated by linseed and China wood oils. The former, containing both linoleic and linolenic acids, gives a"tough elastic film,whereas China wood oil, consisting almost entirely of elaeo­ stearic acid (a differentform of linolenic acid) yields a filmwhich is very tough but lacks extensibility and tensile strength. Similarly in other drying oils, each drying fatty acid gives its specific properties to the resultant film. The quality of the film is influenced also by the manner in which the drying components are arranged within the glycerides, as will be shown later. The influence of solid saturated fatty acids on the melting points or solidi­ fying temperatures of fats and oils has been referred to on page 16. This is also shown in table II. Thus cacao butter, with a high content of palmitic and stearic acids, is solid at ordinary temperatures, whereas other fats with a preponderance of liquid unsaturated acids are liquid. �lost non-drying and semi-drying oils contain large proportions of oleic acid, which solidifies when cooled to 14°C. (57.2°F.). This explains why these oils congeal readily in the cold.

TERRESTRIAL ANIMAL FATS AND OILS

In mammals, fats are found chiefly in the adipose tissue under the skin and surrounding organs such as the liver, heart, and kidneys. The fats from these parts differ slightly in composition. (Lewkowitsch and Warburton 1922.) In fat animals, the fat of the outer part of adipose tissue tends to be more highly unsaturated than that of the inner parts. The character of the body fat may be influenced further by the nature of fats taken in as food. As previously po'inted out, the fat of cattle and hogs be­ comes quite soft and oily when corn and other oily foods are fed continuously. As a general rule, animals of the same species reared under normal conditions show only small variations in the nature of their fat, regardless of climate or geographical location. Any differences that occur are probably due more to conditions of feeding than to the influence of climate. Table IV illustrates the uniform composition of a few common edible fats from different geographical localities.

40 TABLE IV.-Composition of terrestrial animal fats and oils

Beef tallow Mutton tallow Lard Iodine value 38-46 Iodine value 35-46 - - - -- Iodine value ------52-57 North South South

Australian American American Australian American------Saturated acids � % % % % % Myristic ...... 2.0 2.0 2.5 2.0 1.5 Palmitic ...... 32 .2 26 .5 32 .5 25 .0 25 .0 21 .0

Stearic ...... 7.8 22 .5 14 .5 20 .0 23 .0 30 .0

Unsaturated acids Oleic ...... 60 .0 49 .0 48 .3 47 .5 47 .3 43 .0

Linoleic ...... 2.7 5.0 2.7 5.0

It will be noted that these fats contain large proportions of palmitic, stearic and oleic acids : this accounts for their solid or semi-solid nature at ordinary temperatures. The presence of oleic acid and traces of linoleic acid also explains the tendency of edible fats to absorb oxygen and become rancid on prolonged . exposure to air (oxygen). A detailed analysis of other animal fats and oils is not available. Most body fats, however, are of a low degree of unsaturation, with iodine values between 50 and 80. This suggests a composition similar to that of natural lard. Foot oils of the horse, sheep, cow and certain other animals are liquid with iodine values between 65 and 90. These contain large proportions of oleic acid with relatively little palmitic or stearic acids. Neatsfoot oil is chief among this group.

MARINE ANIMAL AND FISH OILS

Oils of this class may conveniently be divided into two main groups, (1) blubber oils from marine mammals and (2) fish oils. The latter group is usually further sub-divided into liver oils and body oils.

BLUBBER OILS In the whale, porpoise, dolphin and seal, most of the body fat is contained in the "blubber" or the fatty layer under the skin. In addition, the sperm whale contains considerable amounts of oil in certain cavities of the head. This oil differs greatly from that of the bl.ubber. Not only is it less highly unsatur­ ated but it contains a high proportion or-a wax-like substance known as "sper­ maceti"*. The oil from the jaw of the porpoise and dolphin likewise differs from that of the body both in unsaturation and in containing amounts of spermaceti. The blubber fat of the whale is almost entirely liquid, a fact that might be adduced from the low content of solid saturated fatty acids shown in table V.

*Spermaceti consists largely of the ester cetyl palmitate-a compound cetyl alcohol and of palmitic acid.

41 TABLE V.-Composition of marine animal and fish oils

---��-----.-� -.--�----�---.------,--,-�.,-- Body oils Liver oils Blubber oils ._ ------�--�------_.. _------_.- - - Whale Whale Herring Jap Men- Cod Cod Dogfish Skate oil oil Sperm oil Fish haden Nfld. Norge liver liver Nfld. Southern Head Blubber -�-- ---�- - -_.,------�- - _._------._-- -- Iodine Iodine Iodine Iodine Iodine Iodine Iodine Iodine Iodine Iodine value value value value value value value value value value 123-142 130-187 139-173 130-150 130-150 120-150 130-160 110-150 110-150 110-150 ------.. _ --- _._------�------Saturated acids 4 Capric C,oH2o02 . . 18 1 Lauric C,2H2402 ... . """ 4.0 7.5 8.0 12 3 t,:) Myristic C14H2802 . . . 6 6 6.0 5.0 6.0 8 8 Palmitic C,6H3202 . . 10 16 8.5 6.5 10 .5 14 .0 10 .0 12 .1 1.5 0.5 Trace 3.0 3.0 2.3 2 2 Stearic C,sH3602 .. 2

Unsaturated acids 6 Lauroleic C"H,202 .. Trace 1.5 1.5 16 Myristoleic C14H2602 . . Trace 0.5 :-l 9.0 10 .5 18 .0 15 .0 17 24 Palmitoleic C,6H,002 . ... 13 15 .5 20 .0 16 .0

Oleic C,sH3402 •.. 14 24 .5 20.5 44 .0 9.0 Linoleic C,sI-IszOz . . .. . 10 30 29 0 31 .0 Traces

Linolenic C,sH3302 ••. Trace 8.0 6 12 C20 acids (up to or more double bonds) .. 26 19 26 .0 30 .5 29 .0 32 .5 4 10.5 12 C'2 acids (up to 5 or more double bonds) .. 19 12 } 10 .0 10 .5 12 .0 18.5 16.0 6.0 C24acids (up to 6 or more double bonds) . A small proportion of the saturated glycerides, however, solidifies at ordinary temperatures and settles out in the form of a pale yellow fat commonly called "stearine". The liquid portion is composed largely of mono-ethylenic fatty acids (i.e. fatty acids with one unsaturated bond) of the CHi, CIS, C20 and C22 series. Amongst these , oleic acid is predominant, constituting from 25 to 30 per cent. of the total oil. The proportion of more highly unsaturated fatty acids is relatively small, consequently, whale oils, with few exceptions, are practically non-drying. Seal oil is slightly more highly unsaturated than whale oil, but the body oils of the porpoise and dolphin are considerably less unsaturated (table II, page 21).

FISH OILS Oil in fishes occurs chiefly in the layer directly beneath the skin, throughout the muscle and in the liver. Some fishessuch as the cod, haddock, ling and others possess very large oily livers which in some cases contain almost all the oil of the fish. This is also true of fish such as the shark, greyfish and others. These oils therefore are commonly called "liver oils". On the other hand many other fishes, notably the herring, sardine, pilchard and menhaden, possess very small livers but extremely oily muscle. In these the oil content of the livers is almost negligible. Oils from fish of this group are kno\vn as " body oils" . In larger fishes such as the halibut, salmon and others, the distribution of oil between the body tissue and liver may vary greatly, depending on the fish, its age, habits of feeding and availability of food. As a general rule, fish with oily livers contain only a small amount of oil in the tissue. Similarly, fishwith a large amount of oil in the muscle tissue have very little oil in the liver. During the spawning period the oil content of all fishes diminishes since at that time most fish cease feeding, and, for energy, depend entirely on the supply of oil stored in the body. Fish-liver and body oils differ from vegetable and animal fats and oils pre­ viously described chiefly in that they contain fatty acids of the C20 and C22 series. These fatty acids may be present to a slight extent as saturated acids but are more extensively present in the unsaturated form containing from one to six ethenoid linkages. Members with four and five of these linkages are common constituents of all fish oils ; it is chiefly by their presence that these oils are iden tified. Tsujimoto (1908) attributes the characteristic odour of fish oils to the presence of clupanodonic acid-one of the C22 series with five unsaturated link­ ages-since on hydrogenating for very brief periods the fishyodour is completely eliminated. The. drying nature of menhaden, pilchard, sardine and other fish oils, result­ ing from the presence of unusual proportions of drying fatty acids of the C20 and C22 series with more than three double bonds, will be dealt with further in a sub­ sequent section. It may be mentioned in passing, that the majority of fish oils fall in the semi-drying class. Liver oils being somewhat less unsaturated than

43 body oils, have usually only slight drying properties as may be inferred from iodine values given in table V, page 42. Ratfish-liver oil is among the few strictly non-drying fishoils. The unsaturated condition of fish oils varies considerably during the season. This may be due largely to feeding conditions and especially to the character of food available. An example of this variation will be found in the section dealing with pilchard oil.

STEARINE

Most fish body oils a�1d whale oils, when allowed to stand at ordinary tem­ peratures (20-25°e.) (68-77°F.), deposit a semi-solid yellow fat commonly called "stearine"*. On cooling still further, the amount of stearine steadily increases until at about O°e. (32°F.), the oil completely solidifies. This is explained by the fact that each individual component glyceride has a definite melting (or solidifying) temperature, and tends to become solid when this temperature is reached. Since, however, an oil is a solution of several glycerides each one of which affectsthe melting point of the other, there is no sharply defined temper­ ature at which any one glyceride will solidify, but rather a temperature range. The precipitation and the composition of stearine may be further illustrated by figure 9. /solid fatty acid /solid fatty acid Glycerine solid fatty acid Glycerine solid fatty acid ", ", "'solid fatty acid "'liquid fatty acid 1 2

/solid fatty acid /liquid fatty acid Glycerine;:::-liquid fatty acid Glycerine,,--liquid fatty acid "'-liquidfatty acid "'liquid fatty acid 4 3 FIGURE 9. Graphical representation of different types of glycerides

For the sake of clarity, "solid fatty acid" in the above has been taken to represent any fatty acid solid at ordinary temperatures and includes the saturated fatty acids above CIO and some of mono- and di-ethylenic members of the C20 and C22 series. The term "liquid fatty acid" represents any fatty acid above CIO liquid at ordinary temperatures and therefore includes only unsaturated members. Glyceride 1 is solid at ordinary temperatures and 4 is liquid. Whether 2 and 3 are solid or liquid depends on the relative melting points of the fatty acids present. If the solid acids in 2 have high melting points, the glyceride will

*"Stearine" and "stearin" are often used synonymously. In this paper the term "stearine" refers to the solid glycerides that form in an oil when it is cooled. The term "stearin", on the other hand, refers to the single substance, the triglyceride of stearic acid, represented as follows :

/stearic acid Glycerine '" stearic acid "'stearic acid solidify and precipitate. The precIpItate, however, may be only semi-solid be­ cause of the presence of the liquid constituent. If the liquid members in 3 pre­ dominate in influence, this glyceride will remain liquid. Fish oils consist of a mixture of all four types of glycerides. Consequently. the stearine at ordinary temperatures contains both saturated and unsaturated fatty acids with a preponderance of the former. Similarly, the liquid portion of the glycerides-that is, the remaining oil-will consist mainly of unsaturated members. These facts have an important bearing on the limitations of the use of drying fish oils as will be seen in a later section.

UNSAPONIFIABLE MATTER

All fats and oils, of both vegetable and animal origin, contain substances which cannot be saponified by alkalies. These are called collectively "unsapon­ ifiablematt er", or in industrial parlance, simply "unsaponifiables". These sub­ stances, though entirely different from glycerides, are not usually regarded as foreign materials because their presence in oils is natural and not accidental. :Most of the components, being fat-soluble, are present in true solution while certain others may be present in the colloidal form, that is, as a suspension of extremely small particles that never settle out. The latter may be removed more or less successfully from the oil by means of filtering earths but the com­ pletely dissolved materials cannot be removed without decomposing the oil in the process. The amount of unsaponifiable matter varies greatly with different types of oils, being highest in certain liver oils, particularly those from certain species of greyfish and shark. Chapman (1927) has reported instances of very abnormal cod-liver and shark-liver oils containing 70 and 90 per cent., respectively, of unsaponifiable components. Oils of this type, however, are not common. The following table (VI) gives the unsaponifiable content of a few common fish body and liver oils. TABLE VI.-Unsaponifiable content of fish oils Body oils U nsaponifiable matter Menhaden . 1 .6 - 2.2 per cent. Sardine . . ... 0.52- 0.86 per cent. Herring .. 0.99-10 .0 per cent. Salmon . .... 0.05- 2.0 per cent. Canadian pilchard ... 0.1 - 1.0 per cent. Eulachon (Oolachan) ...... 17 .0? per cent. Sunfish* . .... 22 .0 -24 .0 per cent.

Liver oils Cod ...... 54- 2.0 per cent. Haddock . l.1 per cent.

Halibut ...... 7.6 per cent. 5.0 -32 .0 Greyfish...... per cent. Shark (Arctic) .. 10 .2 per cent.

*The sunfish is a relatively scarce fish and not caught in commercial quantities. 45 Individual fish body and liver oils do not vary widely in unsaponifiable content as a general rule. Holmes and Clough (1927) examined 111 samples of cod-liver oil taken from the east coast of North America from New York to Labrador and found the unsaponifiable fraction in every instance to be between 0.97 and 1.40 per cent. Drummond and Hilditch (1930), comparing samples of cod-liver oil taken from Newfoundland, Scotland, the North sea, and Norway at different parts of the season, found a variation of only 0.65 to 0.79 per cent. Variations do occur, however, in oils from certain fish caught in widely separated localities. Such variations are shown in oils from fish like the greyfish (dogfish) which is widely distributed throughout the waters of the temperate zones. The unsaponifiable matter from the liver of this fish has been reported as low as 5 per cent. and as high as 32 per cent. The unsaponifiable fraction of marine animal fats and oils may include the following : (1) Higher straight-chain or aliphatic alcohols : cetyl, octodecyl, ceryl, and melissyl alcohols. (2) Sterols : Cholesterol (in animal and fish fats or oils) Ergosterol (precursor of vitamin D). (3) Hydrocarbons : Squalene (or spinacene). (4) Other constituents of unknown composition. These may include the natural pigments of oils, vitamin A, etc. The hydrocarbon squalene forms a large part of the unsaponifiable matter of the liver oils of the elasmobranchs,-greyfishes, sharks, etc. Cholesterol is usually a common constituent of all unsaponifiable matter, in some cases being present to the extent of 50 per cent. It is similar in nature to ergosterol which has been shown to be the precursor of vitamin D. Drummond and Hilditch have observed a close association between the vitamin A potency and the natural yellow colouring matter in cod-liver oil. They found that by partially removing the colour, the vitamin A potency was dimin­ ished accordingly. I t has been shown recently (Euler, Euler and Hellstrom 1929 ; Moore 1929 and 1930; Capper 1930; Olcott and McCann 1931) that carotene, which is a widely distributed naturally occurring pigment, is closely related to vitamin A. Rats, depleted of their store of this vitamin, resume normal growth when small amounts of carotene are fed to them. The liver of these rats yields an oil, which according to colorimetric tests, is rich in vitamin A. The vitamin A activity of vegetable substances, therefore, may be due to carotene which is transformed by the animal body to vitamin A. Carotene itself is easily oxidized and can be adsorbed by suitable charcoals (Ahmud 1931). The vitamin A of fish-liver oils is not so easily adsorbed, and in the oils in which it occurs, is much more resistant to oxidation. It is evident, therefore, that vitamin A is not identical with caro­ tene. This point has been emphasized by Drummond, Ahmud and l\Iorton 46 (1930), who state that the minimum dose of a vitamin A concentrate approx­ imates 0.00005 mgs., which is about 1 per cent. of the minimum dose of carotene. It appeflrs, therefore, that vitamin A can be synthesized by animals from the yellow pigment carotene, and that some animals, notably certain species of fish, have the power to store the synthesized vitamin in their liver, thus providing a very concentrated supply of this substance. The vitamin potency is not necessarily directly proportional to the content of unsaponifiable matter. Thus, some oils containing little of these substances are rich in vitamins, that is, the unsaponifiable portion must be of high vitamin content. This is obviously the type of oil preferred for prophylactic purposes since unsaponifiable constituents other than the vitamins are of little value and moreover tend to impart an unpleasant taste. The value of unsaponifiable matter, therefore, lies chieflyin its vitamin content. Where oils are to be used for other than medicinal purposes, unsaponifiable substances in large amounts are a decided detriment.

REFERENCES

ALSBERG, C. L. AND A. E. TAYLOR. The fats and oils. Stanford University, California. 1928. ARMSTRONG, E. F. AND J. ALLEN. A neglected chapter in chemistry : the fats. J.S. C.I. 43, 28 (207T) . 1924. BROWNE, B. AND G. D. BEAL. The highly unsaturated fatty acids of fish oils. J. Am. Chem. Soc. 45 (1289-1303). 1923. CHAPMAN, A. C. On the natural occurrence in certain fish-liver oils of high percentages of hydrocarbons. Analyst, May. 1917. HAAS, P. AND T. G. HILL. Chemistry of plant products. 4th ed. The Indus- trial Book Co. Ltd., New York. 1928. HILDITCH, T. P. Fats and waxes. D. van Nostrand, New York. 1927. HILDITCH, T. P. Recent advances in our knowledge of the structure of the more common fats. J.S. C.!. 48, 9 (212-216). 1929. HILDITCH, T. P. AND J. A. LOVERN. Head and blubber oils of the sperm whale. J.S. C.!. 48, 50 (359-368T). 1929. HOLMES, A. D. AND R. W. CLOUGH. The chemical and physical characteristics of cod-liver oil. Oil and Fat. Ind. 4 (403). 1927 . . LEWKOWITSCH, J. AND G. H. WARBURTON. Chemical technology and analysis of oils, fats and waxes. 6th ed., London. MacMillan & Co. 1922. MORRELL, R. S. AND H. R. WOOD. The chemistry of drying oils. D. van 5 Nostrand & Co., New York. 192 . TSUJIMOTO, M. On the cause of odours of oils and fats, especially of marine animal oils. J. Coll. Eng. Imp. Univ. Tokyo, 4 (181-191). 1908. C.A . 3, 1223. 1909.

47 VITAMIN A

AHMUD, B. Relation of carotene to vitamin A. J.S. G.I. 50, 12T. 1931. AHMUD, B . AND J. C. DRUMMOND. The relative vitamin A value of the body and liver oils of certain fish. Biochem. J. 24, 870. 1930. CAPPER, N. S. The transformation of carotene into vitamin A as shown by a study of the absorption spectra of rat-liver oils. Biochem. J. 24, 870. 1930. COLLISON, HUME, SMEDLEy-MACLEAN AND SMITH. The nature of the vitamin A constituent of green leaves. Biochem. J. 23, 634. 1929. DRUMMOND, J. c., AHMUD AND MORTON. Further observations on the relation of carotene to vitamin A. J. S. C. I. 49, 291T. 1930. EULER, B., H. V. EULER AND HElLSTROM. The relation of antimony trichloride V. reactions to vitamin A and carotin. G.A . 23, 3013. 1929. MOORE, T. The relation of carotin to vitamin A. Lancet, 2, 380, 1. 1929. MOORE, Vitamin A and carotene. T., Biochem. J. 23, 803. 1929. " 23, 1267. 1929.

" 24, 692. 1929. OLCOTT, H. S. AND MCCANN, D. C. Carotenase. The transformation of carotene to vitamin A. J.B.G. 94, 185. 1931. SEEL, HANS. The chemical nature of vitamin A. G.A . 24, 5805. 1926. G.A . 25, 4024. 1927.

48 SECTION IV.

PRODUCTION AND REFINING OF FISH OILS

4

PRODUCTION OF FISH OILS

In this section will be considered the various types of plants and equipment available for the commercial production, refining, and hardening (hydrogenation) of fish oils. Since many of the methods in general use for the technical produc­ tion and treatment of vegetable and animal oils can also be used for fish oils, a great variety of more or less standard equipment is available. It is obviously impossible to describe all the makes of machinery and equipment used for such purposes. As far as possible, therefore, the discussion has been limited to those that are typical of general practice. In one or two instances, reference will be made to methods or processes not used in general practice but which possess certain novel features. The type of plant equipment used for the production of fish oils depends to a great extent upon the kind of raw material and the character of the finished product. For the purposes of this discussion, raw materials may be classified as follows :- Fish livers, such as cod, hake, shark, greyfish, and others with an oil content of from 30 to 60 per cent. Whole fish, such as herring, sardines, pilchards, etc., with an oil content of from 5 to 20 per cent. Offal of high oil content, from sardine and salmon canneries, etc. Offal of a non-oily nature, from haddock, mackerel, whitefish , and the like, produced in filleting, smoking and drying establishments. The character of these materials differs considerably. For instance, fish livers when cooked do not lend themselves readily to pressing under high pres­ sures since the coagulated mass is very soft and may easily be squeezed through the pores of the filtering cloths. On the other hand, the cooked mass from fresh herring and pilchards can readily be put through a curb press. Also it is obvious that a raw material containing a large amount of oil may require a differenttreat­ ment to that containing only a small amount. Since this work deals primarily with the production of fish oils and not fish meals, only the first three kinds of raw material will be considered.

FISH-LIVER OILS

ROTTING PROCESS

Since the medicinal use of cod-liver oil extends back for hundreds of years, the earlier methods of production of this oil were somewhat crude. In these methods the livers were allowed to decompose in barrels and after the liberated 51 oil came to the top, it was skimmed off. The decomposition of the nitrogenou!? cellular matter of the liver gave rise to many undesirable and obnoxious by­ products which contaminated the oil and gave it a dark colour and a foul odour and taste. Many modifications of this rotting process have been used, such as suspension of the livers in sacks and collecting the oil as it dropped. Since these crude methods yielded inferior oil, they have largely been discarded and cod-liver oil is now produced by superior methods.

DIRECT STEAM PROCESS The bulk of the cod-liver oil of to-day is produced by steaming carefully selected fresh livers in deep conical tanks. These tanks are usually tinned and are kept scrupulously clean. Live steam is let in at the bottom of the tanks with just enough pressure to keep the contents in a state of gentle agitation. When the cell walls have been ruptured and the protein matter coagulated, the oil comes to the top and is either skimmed or pumped off. Drummond and Hilditch (1930) recommend the use of steam at a pressure of 80 to 100 pounds per square inch for the manufacture of medicinal cod-liver oil. They claim that the vitamin content of the oil does not appear to suffer in any way when high pressure steam is employed, while the yield of oil and its separation from the "foots" is better under these conditions. Owing to the high temperatures attained by the use of these pressures, the liberation of the oil from the livers is completed more rapidly, and, what is more important, the treatment ensures the complete inactivation of the enzymes present in the liver material. These authors findthat steam at a pressure of 30 to 60 pounds per square inch is also quite efficient, provided that the steaming time is extended.

VACUUM PROCESS On account of the susceptibility of the oil-soluble vitamins to oxidation, particularly at high temperatures, many processes have been devised for the pro­ duction of medicinal cod-liver oil from the livers under reduced pressure and low temperatures. In figure 10 is shown a vacuum boiler designed to produce first quality medicinal cod-liver oil. During the cooking process, a relatively high vacuum is maintained and the livers are heated by low-pressure steam or hot water, circulated through the jacketed kettle. The process can be watched by suitable glasses mounted at the side of the apparatus. Thermometers and vacuum gauges are provided and the operation can be closely controlled. The equipment provides for the decanting of the supernatant oil and the discharge of the foots through the bottom of the tank.

FREEZING PROCESS American Patent 1,519,779, June 14, 1924, describes a method for the pro­ duction of "non-freezing" medicinal oil from cod-livers without the use of heat. According to the patent this is accomplished by subjecting the fresh livers to a temperature several degrees below the freezing point and maintaining them in a 52 frozen condition until the oils are pressed from them. The apparatus described to accomplish this is a jacketed glass-lined tank in which the livers are placed. A freezing mixture is pumped through the surrounding jacket to freeze the contents. The frozen mass is pressed to extract the oil, the livers being kept frozen during

FIGURE 10. Sco:t's vacuum boiler.

the process. It is claimed that this procedure yields a larger quantity of first­ grade oil, having less odour and a lighter colour than that made by the steaming process. This particular form of manufacture of cod-liver oil has been examined by Mr. W. W. Stewart (1929) at the Fisheries Experimental Station (Atlantic) , of 53 the Biological Board of Canada. It was found that by freezing and pressing, more oil could be obtained from a given sample of livers than was possible by skimming it off in the cooking process. The "foots" (i.e. the residue left after refining an oil, or the solid material left, after removing oil from a substance), from the pressed frozen livers, still contained a quantity of oil, however, that could possibly be recovered as a second-grade material. It is claimed that the vitamin content of oil made by this freezing method was the same as that ob­ tained by the steaming process. Low temperature methods of extraction, however, are open to criticism on the following grounds. Always present in the liver are those fat-splitting enzymes called lipases. As explained elsewhere, these substances split up the fat into free fatty acids and glycerine. Lipases are destroyed by heat but in the freezing method of pro­ duction they tend to accompany the oil (dissolved in minute globules of water) in the active state, and consequently such oil may develop an acid type of ran­ cidity more quickly than if the oil were heated. Therefore, in any process where low temperatures are employed for the production of fish oils, it is better to heat the oil to such a temperature that those active enzymes are destroyed before the final storing. Another factor has been pointed out by Drummond and Hilditch (loc. cit.) namely, that it is quite possible that a part of the vitamins may not be originally in solution in the oil itself. Heat treatment would tend to dissolve these vitamins in the oil prior to extraction, but in the use of cold processes there would be the danger of some of the vitamins remaining in the cellular material of the livers.

ELECTROLYTIC PROCESS An interesting process for the production of fats and oils from animal and vegetable matter is that devised by Rogers, and described in the Chemical Age (1921). This process involves the use of an electrolytic cell composed of carbon and iron electrodes. The carbon is the negative electrode and the iron the posi­ tive. The cells are made of iron pipes, 2-inch diameter, through which passes axially a carbon rod 1 inch in diameter, thus leaving an annular space between the pipe and the rod through which the mixture to be extracted is passed. After passing through a chopper the oil-bearing material is mixed with a warm solution of common salt and the mixture pumped through the apparatus. Direct current is applied at a voltage of 90 to 120 volts. The amount of current passing may reach from 18 to 24 amperes. It is claimed that the passage of the electric current so changes the nature of the material that the oil cells are ruptured and the oil liberated. The mixture comes from this apparatus as a fine emulsion. The inventor recommends separation by a basket-type centrifuge. It is claimed that first-grade oil is obtained within ten minutes from the time the material enters the unit, in yields approximating 99 per cent. In a small unit built by one of the writers (H.N.B.) to test the feasibility of this process, it was found that a great deal of heat was generated during the passage of the current. The mixture coming from the extractor consisted of. a;

54 very fine emulsion that would not separate or "break" when centrifuged at five thousand revolutions per minute. A microscopical examination showed that the cells were indeed broken and the oil liberated, but whether this was due to the passage of the electric current or to the heat developed was not ascertained. It was necessary to break the emulsion by steaming. Solvent extraction processes that may be used for the preparation of fish liver oils are discussed at the end of this section.

FISH BODY OILS The production of oils from whole fishsuch as herring, sardine and pilchard, requires a differenttype of plant from tha� used for the manufacture of liver oils. This is due to the higher water content of the raw material and to the spongy nature of the cooked mass. Nlodern methods for the production of fish body oils may be divided into two types. In the first method the material is cooked, excessive moisture and oil pressed out and the residual matter dried. The oil and water mixture coming from the presses is separated either by heating or by centri­ fugal processes. In the second, the raw material is cooked and the excessive moisture evaporated under reduced pressure and the more or less dry oily material extracted by solvents. Both these systems may be operated as continuous or non-continuous units.

THE DISCONTINUOUS BATCH SYSTEM \Vhere the raw material for production of fish meal and oils is varied as in plants operating on general offal from salmon canneries, or fresh-fish packing establishments, a "batch" or discontinuous system may be operated to advan­ tage. Fish a fev\' days old require a different treatment from those processed in the fresh condition. \Vhen a of rmv material is it is quite often found that it is impossible to operate under strictly fixedcond itions. It is in its flexibility that a batch system proves of value. In this system, each individual is carried out independently and usually there is no arrange­ ment for the entire automatic operation of the whole plant. Unfortunately, most batch systems now operated have been built up gradually. This often r2sults in a plant that does not operate efficiently because the parts are not properly co-ordinated. Quite often during a glut of material, one part of the plant may hold up the remainder due to lack of capacity. A well-balanced batch system may be operated very successfully when the source of supply varies within wide limits both in kind and quality. The equipment of such plants usually consists of cookers, presses, driers, and tanks for settling and storage. Cookers available for batch systems include many of the designs intended for continuous systems. The earlier types consisted of open tanks heated by steam coils. The fishwere dumped in by the barrow load and cooked for a length of time that varied with the condition of the fish, usually about twenty minutes. The more modern cookers available include both pressure and vacuum 55 types. Of the former it is possible to obtain both direct steam injection and jacketed cookers which may be operated up to 60 or 70 pounds steam pressure. The advantage of such pressures is that the sterilization of the cooked mass and the rupture of the oil cells takes place more rapidly. The closed type is far more economical than the open type of cooker. If the cooker is equipped with sight­ glasses its operation can be controlled as closely as that of the open cooker. Vacuum cookers are usually indirectly heated by a steam jacket or closed steam coils. Adequate mixing of the material is provided for by baffles and paddles, the latter operating on a shaft running through well-packed glands. Horizontal or vertical types may be obtained but the former seem to be more commonly used. Such vacuum cookers may be used where it is advantageous to drive off some of the moisture as the material is being cooked. Where high quality oil is to be produced for edible purposes such a cooker may be of advan­ tage. The operation of this type is, however, more expensive than a pressure cooker since power must be furnished both to agitate the material and also to operate the vacuum pump. The latter must be of high capacity and capable of maintaining a partial vacuum of about 20 inches of mercury. The product from this type of cooker may be treated directly with solvents, or pressed and the solid material passed through a final drying process. Presses available for batch systems include the hydraulic and screw types. The former can be used with curbs or, more simply, by building up layers of the cooked material in folds of canvas. In this press, the pressure can be controlled within wide limits-a distinct advantage when a batch of very "soft" material is being treated. \iVith certain kinds of cartilaginous fish, such as greyfish and sharks, the cooked mass must be pressed very lightly and with a steady pressure, otherwise the jelly-like mixture will be squeezed through the filter cloths. This is easily accomplished with hydraulic presses by regulating the speed of the pump. Adequate control may be had over this part of the process no matter how the raw material may vary in character. Screw presses are much faster than hydraulic presses and, more important still, they are continuous. They consist essentially of a conical worm surrounded by a cylindrical curb. This curb may be constructed in either of bvo vv ays. In the earlier types of screw presses the curbs consisted of iron slats arranged radially around the worm. The oil and water was forced through the narrow spaces between the slats, and provision was usually made for the adjustment of the size of these openings. In more recent models the curb consists of a brass cylinder perforated with many fine holes. This cylinder is strengthened by a housing that permits the use of very high pressures. A typical continuous press of recent design is shown in figure 11. The material is fed into the hopper and is carried forward by means of the feed screw into the pressing chamber. The feed screw turns faster than the pressure screw and therefore the material is forced into the pressure chamber under considerable pressure. In the pressure chamber, the diameter of the shaft gradually increases, forcing the material against the brass screen. The outlet of the pressure chamber is closed by means of a cone which

56 holds back and creates a tremendous pressure on the material forced forward by the pressure screw. The clearance between the cone and the outer casing can be controlled by adjustments. Thus the pressure can be controlled to a certain extent. Further control is possible by varying the speed of the screw. The curb principle is also used with hydraulic presses, especially in those designed for the extraction of oil from seeds. Where the simplicity of the curb arrangement is desired, together with close pressure control, such equipment has been found suitable. Hydraulic curb presses, however, are not continuous. A great variety of driers are available for batch system operation. They include such types as steam-jacketed open driers, steam-jacketed vacuum driers, direct fire rotary drum driers and hot air continuous driers. Since this article concerns the production of fish oil, only those driers which are used in solvent extraction will be discussed.

• FIGURE 11. Continuous press (Courtesy of California Press Mfg. Co.).

CONTINUOUS SYSTEM COOKING AND PRESSING This system consists essentially of continuous cookers, presses, driers and oil separating equipment. The entire process is automatic, the material being fed to each unit by means of conveyors, usually of the screw type. Although not quite so flexibleas unit systems, the continuous fishmeal and oil plant has many advantages, chief of which is the large capacity obtainable with a relatively low investment. In industries where the run of fish is of a very short duration, large capacity plants are the only ones economically feasible. For this reason chiefly this type of plant has been used almost exclusively by the menhaden industry of the east coast of the United States, and by the pilchard and sardine industries of British Columbia and California. In figure 12 is shown a plan of a modern fishmeal and oil production plant. The fish are carried up from the hold of the vessel into a V-shaped storage tank by means of a chain and bucket conveyor. At the bottom of the storage tank there is a screw conveyor which leads the fish into the cooker. The entrance to the cooker is protected by an inlet valve. The cooker itself consists of a long 57 cylinder through which runs a conveyor screw. The shaft runs through a gland at the end of the cylinder. In the earlier models of continuous cookers the steam was fed in through a hollow perforated shaft. As the shaft revolved, however, the holes frequently became blocked up with particles of fish flesh. In more recent designs, the steam enters the bottom of the cylinder by means of a series of small inlet pipes placed at equal intervals along the cooker. The steam is thus injected directly into the mass which is propelled through the cooker by means of the screw conveyor. The pressure of cooking varies with the condition of the fish but is usually higher at the feed than at the discharge end. Some manufacturers recommend a pressure of ten pounds per square inch at the feed end and five at

FIGURE Continuous fish meal and fish oil plant. 12. the discharge end. From the cooker the material passes through the outlet valve immediately into the feed box of the continuous screw press, the construction of which has already been described. In the press the hot mass is subjected to a gradually increasing pressure which squeezes out the greater proportion of oil and water together with some dissolved protein and finely dispersed tissue ma­ terial. This mixture (in some cases an emulsion) is piped to the oil-separating system where a part of the suspended solid material is recovered and the greater part of the oil separated from the mixture. The solid material coming from the press is caught by a continuous conveyor and fed into the rotary drier. The dried product is then ground, cooled and sacked.

SEPARATION OF OIL SETTLING TANK SYSTEM In a plant operating on the batch system the separation of the oil from the press liquors usually. takes place in a single tank. This tan� is equipped with 58 heating coils by means of which the liquors from the presses are brought to a boil or to a temperature necessary to break the emulsion and allow the liberated oil to come to the surface. The oil is then pumped offthrough an adjustable pipe. The gurry remaining behind may then be further treated in order to recover the small quantity of oil and protein matter still remaining. In continuous-system plants a series of settling tanks is commonly used, the firsttwo or three being equipped with steam coils. Each tank (usually square or oblong in design) is equipped with adjustable gates which permit the direct over­ flowinto the next tank. Each successive tank is, of course, at a lower level than the one before it. The press liquors are pumped into the first tank and the contents heated, to facilitate separation. The upper layer becomes richer in oil and overflowsint o the second tank where further separation takes place. By the time the oil reache" the fourth or fifth tank it is usually free from water and sus­ pended solids. Each tank is equipped with an outlet pipe at the bottom, by means of which the level of the liquid in the tank may be adjusted. The gurry from the bottom is sometimes pumped to another tank where it is subjected to further heating, yielding another small amount of oil. The settlings from this tank may then be processed for the recovery of the dissolved and suspended pro­ tein matter or "foots". The settling tank system of oil recovery has several drawbacks, If the pressed liquors 'were uniform in consistency and easy to separate, such a system would be entirely satisfactory. This condition, however, does not exist, since the liquor varies from time to time in composition and in degree of emulsification. Sometimes emulsions are produced that are very difficultto break, requiring high temperatures for long periods of time. Then again, by simply allowing the oil to rise to the top, a certain amount still remains emulsified in the "stick" water below and in many cases is discarded. The oil coming from the last of the series of breaking tanks appears to be pure but in reality contains an appreciable amount of suspended tissue material and vv ater. These impurities in the oil seriously affect its keeping qualities and should be removed before final storage. Apart from the loss of oil by the use of the settling-tank system, there is the question of the loss of finely divided meal. It was vvith the object of recovering this meal and cutting down the losses in the oil that engineers applied centrifugal equipment to this industry.

SEPARATION BY CENTRIFUGING Centrifugal equipment has been applied to the production of fishoil and meal in several differentways . Some of these applications are as follows :-

(a) The oil and water is removed from the cooked fish by means of hori­ zontal centrifuges. No presses or settling tanks required. (b) Primary centrifuges capable of removing large amounts of solids are used in conjunction with high-speed clarifiersthrough which is passed all the liquor coming from the screw presses. (c) High-speed centrifuges are used after the press liquor has passed through 59 vibrating or rotating screens. These screens replace the primary centri­ fuge in (b). (d) Centrifuges are used to recover the last traces of oil in the gurry ("stick water") drawn from the bottom of the settling tanks. (e) Centrifuges are used to "clean up" the oil going to storage tanks. Since these methods have been applied with success to the production of fish oil both in Europe and in America, a brief description of each will be given. The Scott centrifugal system. A centrifugal machine designed to treat the whole of the material coming from the cookers, with the eli�ination of presses and settling tanks, has recently been introduced. The centrifuge is of the hori­ zontal type and is continuous. The cage is a solid one, driven by a 15 h.p. motor. The cooked mass is introduced while the machine is in motion and the oil is con­ tinuously removed as it is separated, by means of a decanting pipe which is con­ trolled from the outside of the machine. When it is desired to remove the solid material from the centrifuge, a knife is brought into action which de­ taches the mass from the cage. The distance of the knife from the cage of the centrifuge can be controlled with accuracy. The process consists simply in intro­ ducing the material, centrifuging, decanting the liquid, and stripping out the residue. The meal may then be treated in a solvent ext�action plant, if the oil content is to be further reduced. No operating data regarding this new system are yet available but if the separation of oil and water from the meal proves to be more efficientthan pressing, the simplicity of this method has much to commend it. A sample of herring oil made by this process has been examined in these laboratories and found to be of excellent quality. The Sharples system of oil and meal recovery. A diagram of this system is shown in figure 13. This does away entirely with settling tanks. The liquid direct from the press is fed immediately to a primary centrifuge of the vertical solid-basket type. This machine is driven by a vertical motor directly connected to the shaft by a flexible coupling. This centrifuge takes out the larger amount of finelydisp ersed fishmeal and thus tends to reduce the amount of protein matter going into solution. The liquid discharged from this unit is then pumped through a specially designed heater and then passes through a super-centrifuge which separates the oil from the water. This oil goes direct to storage and is tolerably free from moisture and protein matter. The oil thus reaches the storage tanks in a very few minutes after leaving the screw press, and therefore the danger of oxidation and hydrolysis of the oil during production is to a great extent elim­ inated. The oil content of the discarded waste water is very small and does not warrant further treatment. DeLaval centrifugal system (with vibrating screens). In this system, the liquors coming from the continuous press are passed through either a series of vibrating screens or through a rotating screen. These screens are now supplied by press manufacturers. The greater amount of suspended meal is thus removed and the mixture is then pumped into settling tanks which are steam heated. The separ­ ated oil coming from the last of the settling tanks passes through a centrifugal oil

60 purifier which removes the last traces of moisture and finely dispersed material. The settlings from these tanks may either be discarded or put through the oil purifier. This is necessary especially when fish arrive at the plant in a stale condition. Under these circumstances persistent emulsions are often formed in the presses. It is sometimes necessary to put the greater part of the liquor

Supe,. CenlrifuseOil ,,,,J For�e Ft::lrQfins Wa ler

-Wafer..- ? -Oil -+ Co n veyor Neal

FIGURE 13. Sharples system of oil and meal recovery.

Conf,nuous press . Bowl Handling Tackle

Oil Pu ri flel'

FIGURE 14. eLaval centrifugal system. D

through the centrifuge to prevent the loss of oil. By the use of these screens, the oil and water emulsion is freed from the greater amount of solid materials and consequently the centrifugal machines can be run longer without cleaning the bowls. This system is shown in figure 14. It is estimated that one centrifugal purifier is required for every five tons per hour press capacity. DeLaval system (with breaker tanks). Another system utilizing a centrifugal

61 oil purifieris shown in figure 15. In this method, settling tanks are used to break the emulsifiedliquor coming from the continuous press. The oil from the settling tanks may either be put through the purifier or pumped direct to the storage tanks, depending upon its condition. The emulsion sometimes formed between the oil and water layers may also be put through the oil purifier, after passing through a heat exchanger. The oil-free residue in the settling tanks is discarded.

MISCELLANEOUS METHODS OF OIL AND MEAL RECOVERY The amount of oil and meal remaining in the liquors of the separating tanks varies considerably and is dependent upon a number of factors. First among these is the condition of the fishwhen received at the plant. Fish that have been feeding on so-called "green feed" are prone to give emulsions of oil and finely-

Conti• nuous Pr ess

0;/ Pu rifier OSoffwins at dePi!,sirede fOr Lev draelwing

FIGURE 15. DeLaval system with breaker tanks. divided protein matter which are hard to separate. Stale fish or fish that have been improperly cooked also give these emulsions. Certain cartilaginous fish such as greyfish and sharks yield press liquors very dif-ficult to process. Con­ siderable efforthas been made to finda simple method of coagulating the protein matter causing these emulsions. In addition to the application of heat and centrifugal force described in the preceding sections, some attention has been given to the use of chemical coagulants. The results of some tests made by R. S. Taylor and quoted by R. W. Harrison (1930) are of interest in this connection. Taylor found that aluminum sulphate combined with a small amount of acid, broke the emulsion and precipitated some of the nitrogenous material. Using aluminum sulphate alone, it was found that one pound of the material to twelve gallons of liquor from the presses of a menhaden plant was sufficientto break the

62 emulsion and gives a mixture easy to filter. Ferric chloride was found to be still more efficient. Using a recessed-plate type of filter press to remove the coagulated protein, aluminum sulphate gave a flow of 0.80 gallons per square foot per hour as compared with 1.08 gallons for ferric chloride. Two or three recessed-plate filter presses, therefore, would have sufficient area to handle the effluent from most plants. In this way, the most troublesome emulsions can be broken. Furthermore, suspended solids and about one-third of the dissolved substance can be saved. Since most of the oil lost is contained in these emulsions it is apparent that these losses can be reduced by coagulation. Another simple method found to be fairly efficient in breaking emulsions is to filter the press liquors directly through a filter press as described above, but with the use of a filter-aid, such as filtercel. This material assists in breaking the emulsion and so leads to a high recovery of oil but does not coagulate much of the dissolved protein. A study of the waste liquors from the pilchard reduction plants of British Columbia has just been completed by D. Beall (1933). The following data (table VII) taken from his report show the losses occurring in the effluentfrom settling tanks and from vibrating screens. The weights are based on an average flow of two thousand gallons of effluent per hour.

TABLE VII.-The losses per hour from tank and screened effluent Tank effluent Screened effluent

Oil .. " . . .. 17 gallons 16 gallons

:VIeal...... 2g2 pounds 15g pounds

Soluble nitrogenous material ...... 583 pounds 545 pounds

The vibrating screens retain approximately one-half of the suspended meaL The loss of oil is not greatly reduced. It is apparent that more efficientm eans of oil should be adopted as a loss of 17 gallons of oil per hour is a serious matter.

SOLVENT EXTRACTlON PROCESSES GENERAL In a solvent extraction system the material is usually firstheated to sterilize the material and rupture the oil cells. In this process a certain amount of water is removed. The cooked mass can then be extracted immediately or a part or whole of the remaining water evaporated before subjecting to the action of solvents. The exact place in the process to apply solvent extraction can only be found by actual experiment. In Great Britain, it has been found that the offal from the kippering of herring can be handled by a solvent extraction plant after a short treatment in a steam-jacketed cooker. This offal is very fluid in nature and after a portion of the water has been removed in the cooker, the proteins are coagulated to a thick paste. A portion of the oil separates and may be decanted. The coagulated mass is then extracted without further removal of moisture. The dry finished product contains not more than 2 per cent. of oil. Whole herrings are processed 63 in a differentmanner . There is a greater percentage of solids present in this raw material than in the offal and the characteristics of the cooked masses are quite different. The procedure found to be satisfactory is to cook the herring under a vacuum and at a low temperature until the moisture content has been reduced to about 25 per cent., the exact figure being determined by practical tests. The material is then subjected to solvent extraction. A different method is used in the treatment of such fish as the bream. The fish are macerated and treated in the raw state with a solvent which both de­ hydrates the protein and dissolves out the oil. The meal is freed from traces of solvent and at the same time sterilized by treatment with dry steam. The oil recovered by this process is of excellent quality. It will be realized that the process of solvent extraction is one which can be varied and that the material may be extracted in any condition from the original wet state to the completely dry. A very important factor in the success of any solvent extraction process, therefore, is the kind of solvent used. A solvent for treating a wet material must have the property of taking out moisture as well as dissolving out oil. On the other hand, a solvent used for treating dry material does not have to possess the moisture-extracting property but must be a good oil solvent. There are certain properties, however, which all oil solvents must possess. They must be low boiling in order that the oil and meal may not be damaged during the removal of the solvent. Solvents for this purpose must be non-toxic and without chemical action on the plant itself. A good solvent must also be easily purified, and should have a low latent heat of evaporation and a low specificheat . Finally, it should be cheap and available in large quantities. The properties of a few solvents used in extraction plants are tabulated below (table VIII).

TABLE VII I.-Properties of some commercial solvents

, I Boiling Boiling I Latent , point point Specific Specific heat of Solu- Solubility I Solvent range range gravity heat evapor- bility of water °e. OF. ation of oils Petroleum spirit , ---1-- benzine (Iigroin) . 60-120 140-248 0.67-0.70 ' Good Very slight. , Ethylene dichloride . 80-86 176-187 1. 25 .305 88 cals. Good 0.5% at 20oe . Trichlorethylene .... 87-88 188-190 1.47 0.223 57 cals. Good Very slight. Carbon tetrachloride 76.8 170 1.46 0.203 47 cals. Good Slight. Acetone ...... 56.3 133 0.79 0.506 124 cals. Fair Soluble. Dioxane ...... '" . . 101 .1 214 1.03 Good Soluble.

I

In choosing a solvent for extraction purpI oses, it is necessary to consider the chemical effect of the solvent on the material of which the equipment is con­ structed. The first and last two solvents in the above group have practically no action on iron or other like metals. The three chlorinated compounds all attack iron slightly when moist. Carbon tetrachloride is the most active in this

64 respect. All solvents are more or less toxic in the vapour phase, but of those shown above, carbon tetrachloride is the most toxic. There are a large variety of commercial solvents now available and consequently there is no great difficulty in obtaining one suitable for extraction purposes. The selection of a solvent for the extraction of medicinal oils from fishlivers , however, requires considerable care. Not only must the toxicity of the solvent be kept in mind but its effecton the vitamin content of the oil must also be con­ sidered. In table IX are given the results of a series of experiments made in the

TABLE IX.-Extraction of halibut liver oil with various solvents

Behaviour SbC1, Solvent during Yield Colour Dilution blue Method of extraction and oil removal of per ----at 5 B.U. units per sepanited solvent cent. R Y mgm. oil

-- -- Raw liver Ethyl ether...... 140 cc. foamed 11.3 0.9 22 .0 6/100 67 Ethyl acetate ...... 133 bumped 10 .3 5.0 28 .9 6/160 67 Petroleum ether ...... 124 good 3.4 0.8 13 .5 9/160 44 Carbon tetrachloride ...... 110 good 4.5 40.0 10.0 12/160 33

Cooked liver Ethyl ether ...... 135 foamed 12 .3 1.6 23 .0 11/160 36 Ethyl acetate ...... 1 30 good 10 .5 3.5 25 .0 7/160 57 Petroleum ether ...... 141 good 7.4 2.3 25 .0 13/320 62 Carbon tetrachloride ...... 131 good 10.9 8.5 29 .0 6/160 67

Centrifuged ...... 1.7 0.2 12 .5 7/160 57 Pressed with 50% NaCI ... 2.0 0.5 16.0 7/160 57

Vacuum dried at 80cC. Ethyl ether ...... 113 foamed 16.0 very dark 9/320 88

Petroleum ether ...... 119 foamed 17.2 very dark 9/320 88

Raw frozen

Ethyl ether ...... 143 19 .6 4.3 25 .0 6/160 67 Petroleum ether ...... 128 12 .9 2.0 25 .0 7/160 57 authors' laboratories in which the properties of four types of solvents were investigated. The experiments were made on a large quantity of halibut liver which had been minced and thoroughly mixed. The mixture has an oil content of 23.8 per cent. and a moisture content of 61.6 per cent. 100 gram samples were prepared as shown in the table and extracted first with 100 cc. and then with 150 cc. of solvent. The vitamin A potency of the oils was determined by the SbCla re­ action, and the units calculated to a basis of 1 mgm. of oil (Bailey 1933). I t will be observed that there is considerable variation in the colour and vitamin potency of oils extracted by various solvents, and that the vacuum-dried 65

1) material yields the most potent oils. Furthermore, the absorption of the solvents by the liver material varies greatly with each solvent and also with the prelim­ inary treatment of the liver!'>. These results illustrate the necessity of experi­ mental work in connection with the choice of a solvent for liver oil extraction.

HORIZONTAL EXTRACTORS In figure 16 is shown an illustration of a horizontal digester \yhich may be used for pressure or vacuum cooking. It is steam-jacketed, but cooking may also be effected by open steam under pressure. An efficient condensing system is supplied, and when cooking under a vacuum the amount of uncondensable gases is very small. Thorough mixing is asmred by the rotating blades of the agitator.

FIGL"RE Hi. Horizontal digester.

An oil-decanting pipe and an outlet for the meal is furnished. These cookers may also be used for solvent extraction. Strainer boxes are fitted to the bottom of the extractors and are readily accessible for cleaning or rene\yal. The material can thus be digested, partially or wholly dried, and extracted by a solvent, all in one unit. The last traces of solvent in the meal can then be removed by direct or indirect steam. A vacuum can be used in conjunction with the latter. The solution of oil and solvent is usually pumped to a solvent recovery unit. When first-grade oils are desired, the recovery of the solvent is carried out under a partial vacuum. A compact vacuum distillation plant is shown in figure 17. The steam-heated evaporator is shown at the right. The solvent vapours coming over are caught and condensed in the catch-all and the liquid solvent flows into the receiver. Suitable glasses and gauges make it possible to control

66 FIGURE 17. Solvent recovery system (Courtesy of Ernest Scott and Co., London).

67 the process very closely. The solvent· free dry oil may be pumped or run out of the evaporator when all the solvent has been removed. Where small varying quantities of material are to be handled the two units described above are satisfactory. The solid material is only handled twice, that is, raw material being charged into, and the finished meal coming from the digester. Since it is possible to do both the cooking and solvent recovery under a partial vacuum exhaust steam may be used. A fishmeal and oil plant designed to extract the material in the wet condition is shown in figure 18. The solvent used in this process is acetone, which takes out the water and free fatty acid before dissolving the neutral oil. The steps in this process are as follows. The fishare delivered into the sterilizing macerator where

FIGURE 18. Wilhelm extractor. they are heated to 100°e. (212°F.) for a short period. The material is then dropped into the rotary extracting drum where it is extracted with a definite quantity of acetone at 60°e. 140°F.). After this treatment, the extract is drawn off by means of filter pipes into receiving drums. The solid material is in the meantirpe treated with a fresh amo.unt of acetone. The firstextract is passed through the filter to a recovery still, where the acetone is distilled off and used for another charge. The liquors remaining behind are mainly water and some free fatty acids, since they are dissolved more easily by the acetone than is the neutral oil. The liquid from the second extraction is distilled and the neutral oil recov­ ered. A third and fourth extraction are then carried out until the oil content of the meal has been reduced to the desired level. The last traces of solvent are removed from the meal by indirect heat and steam. Samples of herring oil and 68 meal made from whole fresh herring by this process have been examined in these laboratories and proved to be of good quality.

VERTICAL PERCOLATING EXTRACTOR Horizontal extractors as described above are of value in the treatment of dense material that is liable to pack. Moist or wet material can also be handled by these types of agitated extractors. \iVhere the material is in a coarse dry

FIGURE 19. Simple solvent extraction plant-percolator type (Courtesy of Ernest Scott and Co., London). conditjon , percolation methods can be resorted to. A simple plant based on this principle is shown in figure 19. In this plant there is no agitation of the material. The solvent used is trichlorethylene which is non-inflammable and one of the least toxic of the chlorinated solvents. Consequently the plant can be operated in any locality. The extractor is not jacketed and open dry steam is used for the elimination of the last traces of solvent from the meal. The solvent is recovered from the oil by vacuum distillation. 69 A percolating solvent extraction plant of novel design is shown in figure 20. In this plant dry material, even when very finely divided, can be treated by the percolation process. The material is charged into the percolating tubes (A) of which there may be from one to four. In these tubes the material is treated with warm solvent, which in this case is petroleum benzine, b.p. 90 to no°e. (194 to 230°F.). The solvent containing the dissolved oil is withdrawn through special patented valves (B) . The upper parts of these valves are

FIGURE Semi-continuous solvent extraction plant, percolating 20. system (Courtesy of Ernest Scott and Co., London). perforated, thus allowing the liquids, but not the solids, to pass out to the recovery vessel where the solvent is recovered. The lower part closes off the recovery vessel (C) immediately underneath. The plant becomes semi-continuous, for while the fish meal is being extracted in the percolating tubes above, the extracted material of the previous charge is being subjected to dry heat and vacuum in the recovery vessel below. The last traces of solvent are thus removed. The recovered solvent is then ready to run through the percolating tubes again. Meals of low oil content and oils of excellent colour and low acidity are produced by such equipment. 70 OILY FISH OFFAL The greater part of the fish offal produced in British Columbia consists of halibut and salmon waste, the latter being available in the larger quantity. Halibut are eviscerated at sea and when landed, only the heads are removed. These heads, together with a small amount of "culled" or undersized fish consti­ tute halibut offal. Salmon offal, on the other hand, while consisting chiefly of heads, also contains fins, tails and varying amounts of viscera. Good grades of fish meal can be made from both these materials. A high­ grade oil can also be produced if the raw material is fresh. On account of the high content of fat-splitting enzymes in salmon offal, oils with a high acid content usually result if this material is stale. Both halibut and salmon offal have been successfully treated by "batch­ system" plants. One plant in British Columbia operates almost exclusively on this type of material, the offal being collected from fresh-fish shippers and from salmon canneries in the vicinity. \iVhen sufficient raw material is available to warrant the construction of a moderately large-sized plant, the "batch-system" of reduction presents no great difficulties. The production of fish oil and meal from salmon offalby the above scheme is successful only when a number of canneries are grouped together within close hauling distance of the "reducing plant". vVhen hauls, taking longer than 24 to 48 hours have to be made, the arrangement is not possible, partly because of the added expense, but chiefly because of the rapid deterioration of the offal. Col­ lections of offal have been made from canneries as far as 250 miles from the re­ ducing plant. This long haul was only possible because of the coolness of the weather, but, even at that, the oil produced had a high free fatty acid content and the meal had to be sold as fertilizer. In warm weather, offal brought dis­ tances as short as 15 miles sometimes is badly decomposed. :Vl any schemes have been suggested for reducing salmon offalat canneries in isolated areas. Proposals have been made that each cannery sterilize and partly dehydrate its own offal, sending the half-finished material to a central plant for de-oiling and drying. This arrangement is not practicable on account of the difficulty and expense of shipping the semi-processed offal. The most logical scheme appears to be the installation at each cannery of small compact units for the complete preparation of meal and oil. The economical and technological application of this idea, however, is by no means easy to put in practice. The operating season of a cannery is very short and consequently the overhead and depreciation is very high. Such a unit should therefore be reasonably cheap to install, rugged, compact, and simple of operation, of low operating cost and of such capacity to take all the offal as it comes direct from the cannery. Unfortunately, there is no equipment manufactured that approaches this ideal. The continuous type of plant produces a very good grade of oil and meal from salmon offal. It is too costly, however, and, as shown by the experience of British Columbia canneries, is not particularly well adapted to this type of material. The solvent extraction system possesses the same disadvantages as 71 those of the continuous system in addition to the necessity of a solvent recovery plant. Solvent extraction plants, while capable of producing high-grade fishmeal and oil cannot be operated economically by individual canneries. The successful utilization of salmon offal is a difficult problem. In the opinion of the writers a thorough investigation of the physical and chemical pro­ perties of salmon offal should be carried out. The information gathered would at least indicate the most economical treatment of the material. The work should eventually be done on a semi-commercial scale in order that the results may be directly related to industrial practice.

REFINING

For convenience of discussion, the refining of fish oils will be considered under the following headings-wintering, alkali refining, bleaching, deodorizing, and hardening. The combination of these processes used in the refiningof fish oils depends a great deal upon the use to which the final product is to be put. Thus, if a paint oil is being produced, the process would consist of wintering, alkali refining and decolorizing. Deodorizing may be added, if necessary. The solid stearine removed during the wintering treatment may be processed for hardening. When a raw oil is prepared for the manufacture of shortening itis usually put through the alkali refining, decolorizing, hardening and deodorizing processes in the order named. Many kinds of equipment are used for these processes but since the under­ lying principles are the same, a typical plant for each refining step will be de­ scribed. Since two distinct types of equipment are available for hydrogenation, both will be dealt with.

WINTERING OF FISH OILS By "wintering" is meant the cooling of the oil to such a temperature that a certain amount of the solid glycerides (the so-called "stearine") crystallizes out. This is accomplished in some plants by allowing the oil to stand for a long time at ordinary temperatures. This process, known as "tanking", gives an oil only partly free of stearine but usually very free from moisture and mucilaginous matter. During the tanking process the oil should be kept covered to minimize oxidation. With some fishoils, it is necessary to remove the "stearine" at lower temper­ atures than is possible by drdinary tanking. For this purpose, tanks equipped with coils are used, through which cold water or brine is circulated. It is better to cool the oil slowly so that the more saturated glycerides may be completely precipitated. If the cooling is done too quickly, the oil in the neighbourhood of the cooling coils becomes much colder than that more remote. Some of the less saturated glycerides will then be precipitated in the colder part, while in the warmer the more saturated oil will settle out. In addition, too-rapid cooling brings about a condition known as super-cooling. An oil cooled quickly will remain liquid at a lower temperature than necessary to precipitate the stearine.

72 Precipitation of the solid stearine is a slow process and the slower the oil is cooled the more saturated will the resulting stearine be, that is, the higher will be the yield of stearine-free oil. Various oils require cooling at different temperatures, depending upon the quantity and nature of the solid stearine present. There is a temperature, below which the less saturated, more liquid glycerides start to solidify, and at lower temperatures the stearine produced will contain more and more unsaturated glycerides. The table below gives the yields of clear oil ob­ tained from crude pilchard oil cooled to various temperatures.

TABLE X.-Yield of pilchard oil stearine at various temperatures Temperature Yield of clear oil °e . OF. Per cent. 25 77 96 19 66 91 14 57 84 10 50 71 8 46 45 6.6 45 43 It will be noticed that between 10° and 8°C. (50 and 46°F.), the amount of stearine steadily increases and than tends to become constant. Analysis of the stearine deposited at these temperatures shows that the composition also tends to become constant. That is, 8°C. (46°F.) is sufficient to precipitate the greater part of the stearine. If lower temperatures are used the oil will solidify also. Therefore, for the removal of the maximum amount of stearine in pilchard oil it is recommended that a temperature of about 8°C. (46°F.) be used. The influence of the rate of cooling on the physical character of the precipitating stearine is shown in the following photomicrographs taken through crossed nicols. I t will be noticed from figure21 (1) that the rapidly cooled sample deposits very minute crystals. These take a long time to settle and in doing so carry down appreciable amounts of the liquid glycerides with them. The second photograph shows crystals of stearine deposited by slow cooling. These crystals are large and quite granular ; they settle rapidly and are easy to filter. Figure 21 (1) and (2) represent samples of oil previously alkali-refined and decolorized with an earth. Figure 21 (3) shows the characteristics of the stearine crystals deposited by an unrefinedraw oil, when slowly cooled. These crystals are not as granular or as large as those of a slowly cooled refined oil but are much larger than those obtained by the quick-cooling process. It is obvious, then, that the slowly cooled refined oil gives the best separation of stearine.

ALKALI REFINING The principal object of alkali refiningis to remove the free fatty acids present in the oil. The soap thus formed has certain adsorbent properties and usually carries down with it a certain amount of colouring matter, finelydisper sed tissue material, etc., and finally, a small portion of the oil itself. A certain amount of decolorization is therefore effected by this treatment. A typical alkali-refining

73 FIGURE 21. Photomicrographs of pilchard oil stearin, taken with polarized light 150. 1 ,-quickly. X cooled refined oil; 2,-slowly cooled refined oil; 3,-slowly cooled raw oil.

74 set-up is shown in figure 22. A charge of oil is pumped to the refining tank, which is equipped with agitators to mix the caustic soda thoroughly. The caustic soda solution is pumped from the dissolving tank to a measuring tank placed above the refining apparatus. The amount of lye added depends upon the free fatty acid content of the oil. The strength of the caustic soda solution varies from 16° to 24° Be. The darker the oil and the higher the free fatty acid content the stronger must the solution be. The refining tank is equipped with steam coils and the oil is heated to about 24°C. (75°F.) and maintained at that temper­ ature during the addition of the alkali solution. The mixture is stirred rapidly for half an hour, after which the temperature is raised to between 43 to 46°C. (115 to 120°F.). The treatment is finished when the sample shows a clear oil

FIGURE 22. Alkali refining plant. carrying flocculent black specks in it. To facilitate the separation of the soap or foots, a small amount of sodium silicate may be added and after the foots have settled out completely, the clear oil is drawn through a swinging suction line and pumped to a storage tank. The foots left in the refining tank may be heated to obtain a further separation of neutral oil. They are then drawn offand another charge pumped in. To minimize the loss of oil during this refiningproc ess, careful control should be maintained over the amount of alkali added, the strength of the alkali solu.­ tion, and the temperature at which the process is carried out. The rate at which the mixture is stirred is also of importance since too rapid agitation sometimes produces emulsions that are difficult to separate. 75 BLEACHING The bleaching of an oil is usually effected by using a Fuller's earth or a highly activated decolorizing earth. Activated carbons are also used in small quantities in conjunction with the earths. This process is quite simple and the apparatus required is shown in figure 22. I t consists of a bleaching tank in which the oil may be heated and agitated with the decolorizing earth used; The amount of earth required varies from three to eight per cent., depending upon the type of earth used and the amount of colour to be removed. In vegetable oil refining and decolorization, it is found that the addition of four per cent. of a decolorizing carbon to three per cent. earth will sometimes give the same amount of decolor­ ization effected by six per cent. earth. The temperature at which the decolor­ izing takes place also depends upon the type of earth used. The time of mixing usually runs from 15 to 30 minutes and the oil is then pumped through the filtering press and allowed to drain back into the bleaching tank until it runs clear. To facilitate the filtering, a small amount of filter-aid such as filtercel may be added. With such a material, the oil runs clear from the press very shortly after starting and can then be run directly to the storage tank. While studying the decolorization of British Columbia fish oils, Brocklesby and Moore (1933) investigated the effect on commercial pilchard oil of various earths found in Western Canada. Table XI is taken from their data.

TABLE XL-Quantities of British Oolumbia earths required to give 80 per cent. decolorization pilchard oil

Quantity Colour Colour Type of earth %H2O Opt . of earth removed remaining in earth temp. used (Duboscq) (Lovibond)

Standard activated earth ...... 20 .0 65- 85°C. 30 88 .6 y=1.5 149-180°F. r=O

B.C. diatomite ...... 10 .5 90- 92°C. 5.0 79 .8 y=2.3 194-198°F. r=O.l

B.C. bentonite ...... 8.0 90- 92°C. 7.0 80 .2 y=3.1 194-198°F. r=O.l

B.C. diatomite No. 2 ...... 7 .6 70- 80°C. 5.0 80 .2 y=1.9 158-176°F. r=O.l

B.C. volcanic ash No. 2 ...... 8.9 90-125°C. 7.0 75 .0 y=2.7 194-257°F. r=O.2

Activated B.C. bentonite acid earth ... 3.1 75°C. 3.0 88 .4 y=1.3 167°F. r=O ---- Activated B.C. bentonite washed neutral 4 .2 93°C. 3.0 85.0 y=1.5 199°F. r=D

76 The standard used in this work was an imported high-grade activated earth. I t will be seen that the local earths were all inferior to this standard but since they are all very much cheaper they could be us�d in larger quantities. By a simple acid activation (the details of which are included in the above paper) the efficiency of these low priced earths was made equal to that of the standard. A great many runs have been made with various combinations, and optimal temperatures and amounts of earths found. For further details the original paper must be consulted.

DEODORIZING If the fishoil is to be used as a drying oil the next step in the refining process is deodorization. When it is desired to harden the oil for use in shortenings, the deodorizing procedure follows hydrogenation. Although hydrogenation com­ pletely removes the natural taste and odour, there is imparted to the hardened oil a slight but characteristic "hydrogenation taste" which must be removed when the fat is to be used in food products. This taste is imparted to all hard­ ened fats whether of animal or vegetable origin. There are a great many patents covering the deodorization of oils but the most successful method consists in blowing the oil with superheated steam while under a vacuum. A plant operating on this principle is shown in figure 23. The oil or fat is charged into the deodorizer and heated from 175° to 235°C. (350 to 450°F.) in a high vacuum. The heating may be done by high pressure steam, superheated st�am, electric immersion heaters or by circulating the treated oil through a heater. The latter method is shown in the diagram. When the de­ sired temperature has been obtained, the oil is "blown" with open steam for a short time. In general, the higher the temperature and vacuum (within certain limits) the quicker is the deodorization accomplished. After deodorizing, the hot oil is run to a tank where it is allowed to cool in a vacuum. It is then passed through a filter press and from there to the storage tank. Hardened fish oils offer no difficulties in deodorization. In treating the natural oils, however, some care has to be exercised. The process should be carried 'out at as Iow a temperature and in as high a vaouum as possible. Too long heating of these highly unsaturated oils at high temp,eratures tends to polymerize them. Hydrolysis also takes place if the treatment is carried out at excessively high temperatures. For some purposes, where a highly bodied oil of pale colour is required. this method with the use of higher temperatures is oj value. Reference to this modification is made in a later section of this bulletin. Koro Hashi, of the Physical and Chemical Research Institute at Tokyo, has deodorized fish oils by several methods. One of these cot:lsists in heating the oil for about 14 hours at 280-290°C. (536-554°F.) in an atmosphere of hydrogen. In this process considerable polymerization takes place and the characteristic odour disappears. The author claims that on saponification, heating, or stqring, the fishyodour does not recur. The other methods investigated by Hashi involve polymerization followed

77 by steam distillation in a vacuum and blowing the oil with cold air. The product from each process is claimed to be relatively free from the fish-oil odClur, and if kept at ordinary temperatures does not regenerate it. The deodorization, how­ . ever, is not absolutely permanent since samples treated with sunlight develop an odour, different, however, from that of the original oil.

HARDENING The process by which liquid oils are converted into solid fats by the addition of hydrogen in the presence of a catalyst has been described in a preceding section. Briefly, the commercial process consists in treating heated oil with hydrogen

FIGURE 23. Oil deodorizing plant. under pressure in the presence of a nickel catalyst. There are many types of plants available for carrying out this process, but as they differ chiefly in mech­ anical details, only two types will be dealt with here. The hydrogen for use in the hydrogenation process may be obtained from an electrolytic hydrogen-oxygen plant or from a steam-iron process plant. The latter system has been developed particularly for the production of hydrogen of sufficient purity for hardening purposes. The details of this system cannot be described in this bulletin. BATCH SYSTEM The first hydrogenation plant to be described is the non-continuous type.

78 I t can be obtained in capacities ranging from 1,000 to 30,000 pounds per charge. A diagrammatic layout is shown in figure 24. In this process the equipment is so designed that the oil-catalyst mixture is circulated by pumping and is sgrayed through the top of the convertor into an atmosphere of hydrogen. The convertor is equipped with an agitator for stirring the oil, catalyst and gas. An intimate mixture of the reacting materials is thus effected which hastens the reaction considerably.

PREPARATION OF CATALYST Equipment is available for the preparation of the nickel catalyst either by the "wet" or ,"dry" process. In the wet process, nickel salts are reduced in oil.

FIGURE 24. Layout for hydrogenation plant.

This method yields a very active catalyst, strongly resistant to poisons and there­ fore of long life. Furthermore, the method is simple and economical. A charge of refined oil, mixed with the proper quantity of dry, pulverized nickel salt, is pumped into the catalyst-reduction-tank. The nickel salt is kept in suspension by means of an agitator and the mass brought to the reduction tem­ perature (275-350°C. or 527-662°F.). A small quantity of hydrogen is then blown into the oil and vented to the atmosphere to carry off the gaseous reaction pro­ ducts-water, carbon dioxide, and carbon monoxide. Reduction is continued under controlled temperature until a sample (drawn from the sampling tube) shows a change in colour from green to black. This reduction requires from two to four hours, depending on the time required to bring the oil to the reduction temperature and the speed at which the reaction is allowed to proceed. 79 During the reaction, the oil itself is partially hardened. The reduced mass, on cooling, can be very conveniently cast into blocks and stored for future use, or transferred directly to the catalyst mixing tank. Because of the great activity and the high resistance to poisons, it is seldom necessary to make more than one or two batches of catalyst a week when the plant is operating to capacity. The temperature used in the wet reduction process is considerably below that used in dry reduction ; this is one reason for the greater activity of the catalyst. The preparation of the catalyst by the dry-reduction method requires more elaborate equipment. Because of the high temperature used and the nature of this process, there is an clement of risk involved that does not exist in the wet reduction process. The apparatus is a revolving tube set in a direct-fired furnace. The metallic salt is charged into the tube and the reduction carried out in an atmosphere of hydrogen till the vent gases show little or no moisture. Eight to ten hours are usually required for the reduction, after which the tube is allowed to cool with hydrogen passing through it. The tube is then opened and the reduced nickel transferred to oil or melted fat.

HARDENING PROCESS The catalyst is first mixed with a small portion of the oil to be hardened in a small mixing tank. This mixture is then heated and pumped from the mixing tank to the convertor and the balance of the charge added. The oil is first heated to the required temperature by circulating it through the furnace. With the agitator in motion, hydrogen is blown into the charge through a perforated coil until a pressure of 60 lbs. per square inch is reached. Using a freshly prepared catalyst, such a pressure is not usually attained since the gas is often absorbed as fast as introduced. Since the reaction is exothermic, it is necessary to cool the oil during hardening in order to prevent discolouration of the fat. This is done by circulating the charge through cooling coils and . returning it to the convertor through a spray coil. The temperature of the charge is controlled by the speed of the oil-circulating pump. The convertor may be vented and a vacuum created periodically to remove moisture and inert gases accumulating from impure hydrogen. The time necessary to complete the hardening varies from 20 minutes to 10 hours and depends upon the following factors. 1. Activity and amount of catalyst. 2. Purity of hydrogen. 3. Character of oil or fat,-whether crude, refinedor semi-refined. 4. Type of oil or fat,-whether cottonseed oil, fishoil , etc. 5. Unsaturation of original oil, and degree of hardness desired in finished product. 6. Temperature. The completion of the hardening is usually determined by testing a sample from the convertor for refractive index or melting point. Either test can be made in a few minutes.

80 REMOVAL OF CATALYST After the hardening has been completed, the hydrogen is shut off but the circulation of the hardened oil through the cooling coil is continued until the oil is cool enough to filter. \Vhen this temperature is reached the valve to the filter press is opened and the return valve to the convertor is closed. The charge is then pumped directly from the convertor through the filter press where the catalyst is completely removed from the fat. The press is opened and the nickel removed from the cloth and returned immediately to the catalyst mixing tank for use in the next batch. If the hardened oil is to be stored for any length of time, it is usually put through a chilling roll. This roll is cooled either with brine or cold water. The fat comes from the roll in the form of flakesand can be conveniently sacked. The fat can be stored in a tank in the melted condition but if handled in this way usually darkens in colour. vV hen the hardened oil is to be used for soap-making, it may be pumped direct to the kettles from the filter press . . Oils hydrogenated for shortening are only partially hardened. They are then deodorized and blended with other suitable oils.

CONTINUOUS HYDROGENATION There has been developed recently a hydrogenation plant* with many unique features. I n this system, nickel turnings, nickel wool or nickel wire re­ places nickel powder as the catalyst. The surface of the nickel is first oxidized to form a filmof peroxide. This is done electro-chemically by making the nickel the anode in an electrolytic bath of sodium carbonate. The surface is then activated by reducing it in an atmosphere of hydrogen at 180°C. (356°F.). The construction of this plant is shown in figure This plant is designed 2.5. to hydrogenate five tons of oil a week. The nickel turnings are contained in cylindrical cages, the walls of which are made of nickel gauze. These cages fit into the reaction chambers which are steam-jacketed cylinders. The raw oil is forced by hydrogen pressure through the exit on top of the tank shown at the left of the picture. Here it is mixed with hydrogen and forced up or down through the reaction tubes and then to the separator where the hydrogenated oil is freed from hydrogen by gravity, and cooled. The liberated hydrogen is passed through a trap and recirculated through the system. The reaction is carried out at temperatures between 130 to 180°C. (266 to 356°F.) and at a pressure of 60 lbs. per square inch. The oil is heated for only 10 to 15 minutes during the period of hydrogenation. There are two methods of operating this plant. The oil may either be forced up the reaction tubes by the hydrogen and allowed to overflow into the bottom of the next tube, or it may be fed in the top and allowed to trickle down over the catalyst in an atmosphere of hydrogen, the hydrogenated oil being col­ lected at the bottom of each tube. The firstis known as the "overflow" method and the second the "drip". It is interesting to note that while the rate and

*Bolton and Lusch Patents. Held by Technical Research vV orks Ltd.

81 amount of hydrogenation are the same in both cases, the overflow method pro­ duces a larger amount of "iso-acids" than the drip method. For hydrogenation of highly unsaturated fish oils by this process, therefore, the drip method would be preferable. Since the catalyst is a part of the apparatus and is not mixed with the oil, the latter comes from the apparatus in a sparkling-clear condition, thus eliminating the necessity of filtration. Furthermore, it is claimed that since no earth sup­ porters are used for the nickel catalyst there is scarcely any hydrolysis of the oil during the process. However, the chief advantage of this plant lies in its con­ tinuous action, long life (the nickel cages should last indefinitely) , and the ease

FIGURE 25. Continuous hydrogenation plant. of reactivation of the catalyst. Furthermore, hydrogenated fats of almost un­ varying composition can be produced. Finally, being continuous, the process is easy to control. Using this process, plants with capacities of 25 to 50 tons a week have been constructed and have proven very satisfactory.

REFERENCES

ALSBERG, C. L. AND A. F. TYLOR. loCo cit. ANON. Electrolytic recovery of fats and oils. Chem. Age, 1921 , C.A . V. 15, 954. 1921. ANON. The non-flammable chlorine solvents from ethane and ethylene. Chem. Markets, XXXI , (3) 227. 1932. BAILEY, B. E. The nutritive value of marine products. V. The vitamin A content of ling cod liver oil. Preliminary note. Contr. Canad . BioI. Fish. 7 (31) . 1933. BEALL, D. Losses in the effluent of pilchard reduction plants in British Col- umbia. Bull. BioI. Bd. Can. 35. 1933. 82 BRANION, H. Some observations on the manufacture and vitamin content of cod liver oil and allied oils. Biol. Bd. of Canada MSS. Rept. Exper. Stns. No. 25. . 1928. BROCKLESBY, H. N. AND L. P. MOORE. The decolorization of pilchard oil. Cont. Canad. Biol. Fish. 7 (32). (Ind. Series). 1933. DRUMMOND, J. C. AND T. P. HILDITCH. The relative values of cod-liver oils from various sources. Empire Marketing Board, London. 1930. DURRANS, T. H. Solvents. D. van Nostrand Co. New York. 1931. HILDITCH, T. P. Fats and waxes. Loc. cit. LEWKOWITSCH, J. AND WARBURTON. Loc. cit. MiTCHELL, C. A. Edible oils and fats. Longmans, Green & Co., London. 1918.

83

SECTION V

UTILIZATION OF FISH OILS

INTRODUCTION Prior to the Great War, fish oils other than cod-liver oil, were of little industrial importance. During the war, when the scarcity of oils and fats neces­ sitated the search for new sources of supply, whale oils and to some extent fish oils, came to be recognized as valuable raw materials. To-day, whale oils finda fairly stable market, chiefly because of their usefulness as an ingredient of soap and edible fats. Fish oils, however, have not been developed to the same extent. This may be attributed partly to their peculiar properties and also to the fact that in the early days of the fish-oil industry, little care was given to methods of production. Consequently, low-grade oils were the rule rather than the excep­ tion. Within recent years interest has again been shown in these oils and now that their particular properties are becoming known, their industrial use is increasing. Tables XIIa and XIIb shows the consumption of fats and oils in the United States in 1929 and will give the reader an idea of the relative importance of fish oils. The table includes also the statistics for fishoils in 1925. Similar statistics fOF Canada were not available. The leather industries in 1925 absorbed almost the entire amount listed under "Miscellaneous Industries" for that year and the amount consumed by this industry in 1929 was about the same as in 1925. The amount over and above this in 1929 was taken up in the manufacture of leather substitutes, water­ proof materials, lubricating compounds, animal and poultry feeding and other uses. The following sections will show in more detail the application of fish oils in the various industries referred to in tables XIIa and XIIb.

FISH OILS AS FOODS The utility of fats and oils in the diet lies in their high energy value. When ingested, they are oxidized or "burned" to provide heat necessary to maintain the body temperature and also to supply energy for work done by the various organs and muscles. Any amount in excess of that immediately required for these purposes may be stored in the body, thus forming a reserve supply of food. All fats and oils have approximately the same calorific·val ue. When burned in air their average heat of combustion is 9.3 calories per gram, as compared with 4.0 calories for carbohydrate foods such as sugar and starch. Burned in the body, the available energy is the same, since the oxidation �f the fats is complete. As a rule, oils, being more unsaturated, are more easily oxidized and therefore yield their energy more readily.

87 TABLE XIIa.*-Factory consumption of fats and oils by industries : 1929. (Quantities in thousands of pounds)

I All industries I "Shortenings" Margarine S -, ------.------.- � .-�----- .------Cottonseed oil . - 1,372,295--- 1,161,848 30,173 �5 33 Peanut oil . 11,851 3,586 6,306 1 :1,��667 I Coconut oil . 652,617 72,145 185,507 393,914 Corn oil. 56,755 25,459 25,602 Soya bean oil . 17,903 82 11 6,396 Olive oil, edible . 2,067 23 O live oil, inedible . 5,858 2,375

Sulphur oil or olive foots ...... 38,875 38,448 Palm-kernel oil .. 56,598 11,824 1 44,532 Rapeseed oil .. 13,327 138 132 Linseed oil . . . 501,235 1,916 Chinawood oil ... 97,474 Vegetable tallow . .. 8,470 I 8,404 Castor oil ..... 28,835 3,730 Palm oil .. 198,017 1,191 1,523 178,851 Sesame oil . 10,076 5,215 4,835 Perilla oil .. 2,639

Other vegetable oils . ... 2,588 102 29 1,714 Lard ...... 45,869 23,123 22,628 Edible animal stearin . 52,245 44,138 6,135 503 Oleo oil . .... 56,360 7,553 48,226 339 Tallow, edible . 28,452 25,556 21 1,782 Tallow, inedible 514,755 451,835 Grease . .. 227,612 154,288 Neat's foot oil .. 6,330 Fish oils. 188,102 14,921 130,634

Total 4,197.175 1,396,881 300,560 1,618,953

.- Fish oil statistics--1925 . 129,653 94,754 !

Fats have further importance as foods because of their intimate association with three important accessory food substances, namely, vitamin A, vitamin D, and vitamin E. These, while not foods in themselves, are necessary in the diet for the proper utilization of foods by the body. Vitamin A is essential to growth and resistance to disease ; vitamin D, the anti-rachitic factor, is necessary for the proper calcification of bone, teeth, etc., and vitamin E is the anti-sterility factor. All three are fat-soluble and are found to a greater or less degree in fats and oils of animals. The firsttwo are present to an exceptional extent in fishoils , notably in certain liver oils. This explains the medicinal value of these oils. Vitamin E occurs along with certain vegetable oils, especially in the wheat germ. Raw fishoils , despite their energy value and vitamin content, are not suitable as commercial edible oils for two reasons. First, because of their highly unsatur­ ated character, they are very susceptible to rancidity and rapidly become un­ palatable when exposed to air. In the second place, solid rather than liquid fats

88 TABLE XIIb.*-Factory consumption of fats and oils by industrials: 1929. (Quantities in thousands of pounds) Miscel­ Paint and Printers' Linoleum Textiles laneous varnish ink and oilcloth industries

Cottonseed oil ...... 96 12 3 13,130 Peanut oil ...... 43 249

Coconut oil ...... 49 1,002

Corn oil ...... '" ...... 364 46 5,284

Soya bean oil ...... 5,815 71 3,229 267 2,032 Olive oil, edible ...... 2,044 Olive oil, inedible ...... 2,508 975 Sulphur oil or olive foots ...... 262 165 Palm-kernel oil ...... 179 62

Rapeseed oil ...... ' .... 95 148 12,814 Linseed oil ...... 340,166 23,894 112,855 161 22,243 Chinawood oil ...... 88,386 437 5,963 17 2,671 Vegetable tallow ...... 42 24 Castor oil ...... 3,287 36 522 13,11� 8,145 Palm oil...... 7 7 540 15;898 Sesame oil ...... 2 , 24 Perilla oil ...... 2,573 10 56 Other vegetable oils ...... 240 301 172 Lflrd ...... 118 Edible animal stearin ...... 1,469

Oleo oil ...... 17 27 1 187 Tallow, edible ...... 9 1,084 Tallow, inedible ...... 42 6 1,351 61,521

Grease ...... , 524 381 344 72,075 Neat's foot oil ...... 21 6,309 Fish oils ...... 10,602 50 10,141 1 21,753

------·------·1 1-----1 --1 - Total ...... 452,207 29,950 133,018 19,100 251,506

Fish oil statistics-1925 ...... 9,029 9,154 16,716 are preferred in the modern diet. For these reasons raw fish oilsare not used as foods except by natives in certain isolated coastal regions, such as along the coast of northern British ' Columbia and Alaska. There, the oil of the eulachon (oolachon) or candle fishhas always formed an important part of the diet of the Indians, although its use is diminishing as other foods are becoming more easily available. HARDENED FISH OILS While not suitable as commercial edible oils in their raw state, many fish oilst can be converted by the hydrogenation process into solid or semi-solid fats. These fats are wholesome and palatable and possess all the qualities of a pure

*Table by courtesy of U.S. Dept. of Commerce. tThose fish oils of low unsaponifiablecontent are more suitable for this purpose.

89 food product. The process, as described on page 78, is essentially one of con­ verting unsaturated oils into saturated fats. Thus, hardened fish oil is entirely differentfrom the original oil ; it is solid, odourless, tasteless, and much less prone to become rancid. The hardness and melting point of the product depends on the degree of hydrogenation as well as on the composition of the original oil. Therefore, by regulating the treatment, products ranging from liquid to hard fats may be obtained. Hardened fish oils as a rule are not used alone in the manufacture of edible products but are blended with vegetable oils such as cottonseed, peanut, sesame, and soya bean oil. The blending may be done either before or after hydro­ genation, according to the product desired. In the manufacture of certain types of fats, the oils selected are first blended and hydrogenated to the desired con­ sistency or melting point. For other types, the reverse procedure is used : a single oil or a mixture is first hydrogenated to a hard fat of comparatively high melting point. The product is then reduced to the desired consistency by mixing it with refined oils, or partially hydrogenated oils. The latter are preferable, being less subject to rancidity. By varying the selection of oils and controlling hydrogenation, the manufacturer can, within limits, adjust the properties of the product to suit specificpu rposes.

SPECIAL FATS The following are some of the special kinds of fats used in the preparation of modern foodstuffs. SHORTENINGS l\I anufactured shortenings may be "simple", i.e., a single oil hydrogenated, or "compound"-consisting of a number of oils blended and hardened as de­ scribed above. In either case the hardened product is usually finished off by subjecting it to an intensive mixing operation in which air is beaten into the fat to form an emulsion. The amount of air thus incorporated may run as high as 10 per cent. by volume. The finished material is very uniform and much whiter and smoother in appearance than the original . As yet no satisfactory method has been developed for measuring the short­ ening quality of fats ; this property can be determined only by actual baking experiments. It is well known, however, that the shortening efficiency of a fat depends chieflyon its emulsifying properties which in turn depend on the melting point and the consistency, particularly the latter. As a rule, these two properties are very closely related in individual fats but may diverge considerably in blended products. Thus, shortenings may have the same melting point but may vary in consistency all the way from firm to soft. It is on this property that the emul­ sifying power of a shortening depends. By the emulsifying property of a fat is meant its capacity to form an emulsion with air, water, milk, etc., when beaten together. Some fats, mixed with sugar, eggs, etc., and beaten or stirred vigorously, will hold enough air to increase the volume of the batter 70 per cent. This emulsification-commonly known as

90 "creaming"-is mainly responsible for the proper distribution of fat throughout the baked goods and also for the texture and "lightness" of the product. When the batter is placed in the oven, the fat melts and the air collecting in small cavities or pockets throughout the baking mass expands, giving it a light spongy structure. The creaming properties of fats are furthermore influenced greatly by temperature and the rate of mixing. Most commercial shortenings have their maximum creaming efficiency at about 75°C. (167°F.).

MARGARINE This name is given to various types of butter substitutes made by blending suitable fats with milk. The composition may differ widely and may include animal fats, "revived" butter, hardened vegetable fats and hardened whale and fish oils. If the product is to be for table use, the fats are blended so as to give a compound melting at about 25°C. (lOO°F.). The mixed fats are first melted and thoroughly emulsified with "ripened" (specially soured) milk. The fluid emulsion is then solidified by chilling between cold rollers. It is finallysalt ed, coloured and "plodded", giving a product often difficult to distinguish from butter in taste and appearance.

CONFECTIONERY FATS These are used in chocolates, toffee and other kinds of confectionery. Cer- tain natural vegetable fats such as palm-kernel oil and cacao butter are preferred for this purpose because they possess the desired brittleness and at the same time have a relatively low melting point. Oils hydrogenated to the same degree of brittleness usually have too high a melting point. Fats used in chocolates are nowadays usually subjected to a very slight hydrogenation treatment since it has been found that the troublesome defect known as "blooming" can be over­ come in this way.

FRYING FATS The main drawback to most natural fats for frying purposes is the ease with which ·they are broken down by heat. Thus, when used in the frying pan they smoke readily, giving rise to irritating volatile products, and also to an accumul­ ation of free fatty acids of low molecular weight. Hardened oils, on the other hand, are much more stable to heat. This is particularly true of hydrogenated fish and marine animal oils because of their relatively high content of the higher­ melting C20 and C22 fatty acids. The smoking temperature of lards ranges from 188 to 204°C. (370 to 400°F.) while that of hydrogenated oils ranges up to 260°C. '(500°F.), depending on the oil and the extent of hydrogenation. 'With these fats, higher frying temperatures can be used, and the surface of the material in the pan is seared, thus preventing the loss of juices, and reducing the penetration of the fat into the product. I t is becoming a common practice

91 among lard manufacturers to hydrogenate natural lard, thereby saturating the unsaturated glycerides and Improving the stability of the product towards oxygen and heat as well as improving the shortening qualities.

SALAD OILS

Oils for salads and mayonnaises consist chiefly of vegetable oils slightly hydrogenated. The hydrogenation treatment given is just sufficient to partially saturate the more highly unsaturated fatty acids of the linolic and linolenic types, thus producing oils which are less susceptible to rancidity. From the foregoing it is seen that the hydrogenation process has made it possible not only to use a great many oils hitherto of little commercial importance but also to produce fats with many qualities lacking in natural fats.

NUTRITIVE VALUE OF HARDENED FATS

In hardening oils for food purposes, the digestibility of the product must be considered. To be completely digestible, fats should melt readily at body tem­ perature so as to be easily emulsifiable by the gastric juices of the stomach ; other­ wise they cannot be completely hydrolysed in the time available. Oils, being liquid to start with, are more easily emulsified than fats, and consequently more easily digested. The relationship between melting�point and digestibility is illustrated by the following data (table XIII) obtained from experiments with animals. (Langworthy 1923.)

TABLE XII I.-Digestibility of hardened fats

Digestibility Fat or oil used Melting point (Per cent. utilized)

Cottonseed oil ...... Liquid 97 .6

Cacao butter ...... 28-33°C. (82-9PF.) 94 .9 · Hardened peanut oil .. 52.4°C. (125°F.) 79.0

(Body temperature 37°C. or 98.9°F.)

The hardened fats of commerce have melting points ranging from 33 to 41°C. (91 to 106°F.) and are equal in digestibility to common natural fats such as lard (m.p. 38 to 40°C. [100 to 104°F.]) and butter. Fats melting very much above body temperature are only partly utilized by the body. It is evident that the diges­ tibility of hardened fats can be ensured since their melting points can be con­ trolled by the manufacturers. On this continent fish oils hardened for edible purposes are used chiefly in the manufacture of shortenings. To qualify for this purpose they must be of low unsaponifiablecont ent and also be available in large quantities. Among the fish

92 oils that meet these requirements are Canadian pilchard oil, California sardine oil, menhaden and certain herring oils. According to statistics available, the amount used annually in shortenings now exceeds 7500 tons. As yet, no hardened fish oils are used on this continent in the manufacture of margarine nor is whale oil used in the manufacture of edible fats. In Europe, on the other hand, particularly in the Netherlands, Germany and Russia, the manufacture of margarine from hardened fishoils and animal fats has become an established industry. Whale oil from the Norwegian south-sea fisheries is the chief oil used, but fishoils from the United States and Canada are also imported. Much research is being conducted in various countries on the selection, blending, and hardening of natural oils for food purposes. In addition, much attention is being given to the incorporation of vitamins and other substances (anti-oxidants) to improve the nutritive and keeping qualities of fats. Fish oils will no doubt be used to an increasing extent in this field.

MEDICINAL USES

COD LIVER OIL

Fish-liver oils have been used for medicinal purposes for many hundreds of years but until lately little attention has been paid to colour, odour and general quality of the product. Indeed for many years, the pharmacist judged the quality of the oil by the depth of its colour. \Vhen the rotting process, by which these oils were obtained from the livers of the fish, was superseded by more modern extraction methods, a paler oil with almost no odour or taste was pro­ duced. At first,this nevv product was regarded with disfavour at the dispensary, but later, when the nature of the active constituents was understood, the modern product became appreciated. The beneficial values of cod-liver oil feeding had been variously ascribed to its iodine content, its high content of unsaturated acids, and other constituents. It was not until 1912 that the class of substances now called "vitamins" became known. These substances are very important in the diet since they control the assimilation and use of certain foods taken into the body. Three vitamins, A, D, and E, are soluble in oil and the first two are found in their greatest potency in certain fish-liver oils. Vitamin A is necessary for the growth and maintenance of the body. Furthermore, it serves to increase the resistance of the body to bacterial infection. Recent work has shown that ade­ quate amounts of vitamin A in the diet reduce the possibility of bacterial invasion of the mucous membranes of the ear and nasal cavities. Vitamin D is the anti­ rachitic vitamin necessary for the proper development of bone in the young animal. In children suffering from malnutrition, the lack of vitamin D is evi­ denced by rickets, faulty tooth formation and sometimes by defective hearing

93 due to improper formation of the ear bones. For many years cod-liver oil has been recognized as an efficientremedy for these troubles. The other oil-soluble vitamin, of interest to poultry and stock-breeders, is the anti-sterility vitamin E, essential for normal reproduction. This vitamin is pre­ sent in cod-liver oil in extremely small amounts. Since cod-liver oil has become so widely used for medicinal purposes because of its high potency of vitamins A and D, it has become a standard with which other oils are compared. It must be remembered, however, that the vitamin potency of cod-liver oils varies considerably. Modern producers, therefore, usually test each batch of oil before putting it on the market and guarantee a certain minimum vitamin content. The use of vitamin-potent oils for animal feeding is becoming more general. Stock-raisers, poultrymen, and breeders of fur-bearing animals have come to realize the benefits derived from feeding these substances. Manning (1929) lists the following possible benefits that may be obtained by the use of these oils : promotion of growth, improvement of calcium assimilation, increase in the iodine content of milk, reduced mortality in baby chicks, prevention of ruffled plumage in poultry, increase in egg production, and the prevention of leg weakness in chicks. I t has not yet been shown conClusively that cod-liver oil feeding improves the hatchability and fertility of eggs. Breeders of fur-bearing animals find that cod-liver oil improves the general health of their animals and also brings about a marked improvement in the fur. The use of medicinal grade cod-liver oil for animal-feeding purposes is pro­ hibitive, owing to the high cost. A lower grade oil known as poultry-grade oil, or simply cod oil, is sold for this purpose. It consists of second grade cod-liver oil mixed with oil from other fish livers. This oil is usually of a dark colour and disagreeable odour and resembles the cod-liver oil produced by the rotting process. Samples of this oil tested in these laboratories have shown vitamin D potencies ranging from 50 to 60 per cent. of that of medicinal cod-liver oil.

VITAMIN POTENCY OF OTHER FISH OILS Large quantities of fishoils other than cod-liver oil are now being produced commercially and can be obtained more cheaply than either medicinal or poultry­ grade cod-liver oil. The determination of the vitamin potency of these oils, therefore, becomes of great importance since, if in any way comparable, with cod­ liver oil in their prophylactic efficiency, they will be of value in animal feeding. In the following paragraphs a chronological account is given of some of the more recent work done on these oils. This is not exhaustive, but will show the pos­ sibilities of these cheaper oils in animal feeding. Holmes (1924) showed that 0.8 mg. per day of hake-liver oil was sufficient to cure rats sufferingfrom vitamin A starvation, while more than 1 mg. per day of haddock-liver oil was required to effect a cure. The author states that 1 mg. 94 of a good grade of cod-liver oil was required to bring about the same amount of recovery. Holmes and Piggott (1925) investigated the vitamin A content of oil extracted from three spawning sockeye salmon-one male and two females. They found that doses of this oil as high as 11.6 mg. per day were not sufficientto bring about a r�sumption of growth in rats sufferingfrom vitamin A starvation. They point out, however, that this does not necessarily mean that there is no vitamin A in canned salmon. The liver oil of the puffer-fish was shown by Hess and Wienstock (1926) to be a very potent source of anti-rachitic vitamin D. On testing this oil biologically, it was found to be at least fifteen times as potent as the most active cod-liver oils. The vitamin A content of Pacific coast dogfish (greyfish) was reported by Brocklesby (1927). Comparison was made with a sample of medicinal cod-liver oil and it was found that the vitamin A potency of the dogfish-liver oil examined was greater than that of the standard cod-liver oil samples used. Bills (1927) investigated a large number of fish oils for their vitamin D �ontent. The following list (table XIV) , taken from his data, shows the relative vitamin D potency of some of the more important commercial fish oils.

TABLE XIV.-The vitamin D potency of various oils in comparison with cod liver oil

No. of Relative Source and description of oil samples potency

Cod-liver, Newfoundland medicinal ...... 500 100 Goosefish-liver (Lophius piscatorius) Boston ...... 1 100 Herring, Newfoundland ...... 4 100

Menhaden, Chesapeake bay ...... 5 75 Sardine, California ...... 2 75 Shark-liver, Newfoundland ...... 1 75

Salmon trimmings, Pacificcoast ...... 3 20 Dogfish-liver, Newfoundland ...... 2 3

The vitamin D potency of the liver oil of the dogfish was also investigated by Brocklesby (1929). Several samples from different localities were examined and the value varied from less than 10 to 30 per cent. of the potency of medicinal cod-liver oil. Asmundson, Allardyce and Biely (1929) investigated the use of dogfish-liver oil and pilchard oil in the feeding of poultry. They report that dogfish-liver oil contains vitamin D but the potency varies rather widely and is decidedly lower than that of cod-liver oil. Pilchard oil gave more uniform results but was not so potent as cod-liver oil. Vitamin D potency of commercial pilchard oil was reported by Brocklesby and Denstedt (1930). A highly uniform potency was found and the oils exam­ ined were equal, if not superior, to a medicinal cod-liver oil, used as a standard.

95 An examination of six of the more important commercial fish oils has been reported by Nelson and Manning (1930). In the vitamin A tests it was found that sardine, Alaska herring and tuna oils contained about li10th the amount of vitamin A found in cod-liver oil. Maine herring oil contained about half as much as the Alaska herring oil. The authors were unable to demonstrate the presence of vitamin A in menhaden oil. They found that salmon oil had the highest vitamin A content of the commercial fish oils examined, being one-third as potent as medicinal cod-liver oil. Assigning to the vitamin D value of cod­ liver oil the arbitrary figure of 100, the oils tested are listed as having the following proportions ; Tuna ...... 125 Sardine .... . 100 Menhaden ...... 75 Salmon ...... 50

Alaska herring ...... 30 Maine herring ...... 15 ' The vitamin A content of commercial pilchard oil was reported by Finn (1931). No attempt was made in this report to evaluate the oil quantitatively, but the author concludes that the results indicate that it is possible to produce an oil containing vitamin A from the pilchard. In a preliminary report on the vitamin content of Canadian canned salmon, Bailey (1932) showed that the vitamin D content of the oil of canned pink and sockeye salmon very high. Table tak�n from his report, tends to show 1 is XV, that there is hardly any difference between the potency of the two sorts of oil but that there might be a slight difference due to locality. However, conclusions regarding this geographical variation cannot be made until a larger number of samples has been examined.

TABLE XV.-Vitamin D value of canned salmon oil

. �.-- ---... ����������- Vitamin D potency Kind of salmon Locality caught (relative to cod-liver oil 100) Pink. Butedale . 67 Pink ... Johnstone straits 88 Pink. Fraser river ... 88 Sockeye . .. Skeena river . 67 Sockeye .. Rivers inlet . 88 Sockeye ... Fraser river ... 88

It will be seen from the above account that many oils other than cod-liver oil may be used to advantage in animal feeding. Since none of the above samples were prepared particularly with the view to conserving their vitamin content, the values reported should represent the potency of the average commercial oils as now produced. It is quite possible that a higher and more uniform grade of oil may be produced when improved methods of manufacture are adopted. 96 Quite recently (1931), some of the more progressive firms producing Cali­ fornia sardine oil have placed their product on the market for animal feeding purposes. The oils offered �re biologically tested for vitamin D potency, using a standard technique, 'with chickens as the experimental animal. Extensive tests have shown that sardine oil gives results which are equal, if not superior, to those obtained when equal amounts of cod-liver oil are fed. In eight weeks, chickens fed the Wisconsin Rachitic Diet gained 500 grams on one-quarter per cent. sardine oil and 460 grams on one-quarter per cent. cod-liver oil. The ash content of the leg bones was 46.00 and 45.87 per cent., respectively. Up to the present no extensive use has been made of similar oils in Canada. Canadian pilchard oil has a vitamin D potency equal to that of medicinal grade cod-liver oil and therefore constitutes a cheap source of this anti-rachitic factor. ' Samples of pilchard oil tested by the Department of Agriculture, Ottawa (1932) have proven to be equal to cod-liver oil for poultry-feeding purposes. There is no doubt that this oil will find a large Canadian market when its prophylactic value becomes more widely known. In regard to oils with a high vitamin A content, an interesting development has recently taken place. It has been found (Schmidt-Nielsen 1929) that the oil from halibut livers is extremely potent in vitamin A, colorimetric tests showing a value 50 to 100 times that of good medicinal grade cod-liver oil. Halibut livers contain from 10 to 20 per cent. of oil but the yield of livers is very small, averaging about 25 lbs. per 1200 lbs. of. fish. The fishermen collect the livers and obtain a fair price for them. The livers are steamed and drained at Prince Rupert and the sterilized material is frozen and shipped to the laboratories of an eastern pharmaceutical company where the oil is extracted for medicinal use. Other liver oils of high vitamin A content are obtained from the black cod, ling cod and the long-jaw. These will be discussed in detail in a later section.

FISH OILS IN SOAPS Soap is made by treating mixtures of fats and oils with alkalies such as lye (sodium hydroxide) or potash (potassium hydroxide), as described on page 25. The mixture of soaps thus produced is the "soap" of commerce. The sodium soaps are harder and less soluble than the potassium soaps and are used in the manufacture of ordinary household soaps. The potash soaps are used for such special purposes as liquid soap, surgical soap and certain kinds of toilet soaps. Soap may be made either by the boiling process or by the so-called cold process. In the former the -requisite amount of fat and lye is boiled by open steam coils until saponification is complete. In the cold process the oil and lye, previously heated to prevent stiffeningwhen mixed, are stirred together without any additional heating. The heat Qf the reaction is usually sufficientto carry the process almost to completion. Soaps made by the latter process usually contain free fat and free alkali and consequently all the finergrades of soap are made by the boiling process. 97

7 Since very few fats and oils yield entirely satisfactory soaps when saponified by themselves it usually is necessary to blend them and thereby combine their properties. The proper selection of suitable fats and oils to produce specific properties in a soap requires much experience and some knowledge of the pro­ perties of the soaps of the individual fatty acids.

THE NATURE OF FISH-OIL SOAPS Soaps from fish oils are in general similar to those from other oils but as a ' rule differ from them in certain characteristics. In the first place, being of more complex composition, the "soap" from individual fish oils includes a wider range of soaps than that from other oils. Secondly, fish oils are characterized by their relatively high content of fatty acids of the C20 and Cn series. The sodium soaps of the saturated members-arachidic and behenic acids, are soluble only at higher temperatures. Those of the monoethylenic acids are slightly soluble at ordinary temperatures while the more highly unsaturated soaps are softer and quite soluble. The potassium soaps especially possess good emulsifying properties at ordinary temperatures. Comparing the composition of fish oils and other oils, therefore, it is fairly easy to anticipate the difference in their respective soaps. That from fish oil is usually softer and has a greater capacity to take up water. More important still, soap from fishoils usually has a greater temperature range ; that is to say, because of its more complex composition, the temperature optima of the component soaps are spread over a wider range. The potassium soaps are very soft and soluble, and are used extensively in industry as emulsifying agents. Furthermore, they make excellent soft soaps. Despite their valuable qualities, however, fish oils until recent years have been used only to a limited extent in the soap industry, and only in the manu­ facture of low-grade soaps. The factors limiting their use were chiefly two, namely, (1) the fishy odour, and (2) inferior keeping qualities of the soap.

ODOUR In former times when little care was taken in their production, fish oils usually possessed a very disagreeable odour due to decaying tissue matter left in the oil. This odour could not entirely be eliminated by saponification ; conse­ quently, soaps made from these oils were of inferior quality. To-day, with im­ proved methods of production and refining, the odour of putrid fish is entirely eliminated. Fish oils of good grade possess a characteristic odour which is not unpleasant and which may be masked by aromatic substances. Tsujimoto (\oc. cit.) attributes the odour to the very highly unsaturated fatty acid-clupan­ odonic acid (5 double bonds)-present in most fish oils. He discovered, further­ more, that the odour can be eliminated entirely by hydrogenating these oils for a very short period. The second factor, i.e. the inferior keeping quality of fish-oil soaps, is the chief objection to the use of raw fish oils to-day. As pointed out previously, fish oils are very susceptible to oxidation. Consequently, when exposed to air, the 98 soaps readily absorb oxygen and develop a disagreeable, rancid odour. Further­ more, the more highly unsaturated components on oxidation deteriorate or break down and slowly change in properties. These defects also can be entirely over­ come by hydrogenation. Certain fishoils , notably the liver oils of some species of shark and greyfish, are further limited in their usefulness for soap purposes by their high content of unsaponifiable matter. These constituents, as previously pointed out, are not glycerides and cannot be saponified. Furthermore, they are removed only with difficulty. Consequently, fats and oils containing more than about three per cent. of these substances are generally avoided by the soap-maker. Practically all commercial fish-body oils contain about the same amount of unsaponifiable matter as do commercial vegetable oils, that is, less than one per cent.

SOAPS FROM HYDROGENATED OILS With the introduction of commerCial hydrogenation it became possible to use fish oils for the manufacture of high-grade soaps. The hardening process used for the production of edible fats from fish oils is described in Section IV. As a result of the treatment, the highly unsaturated fatty acids responsible for odour and deterioration are converted into less highly unsaturated or completely saturated fats, depending on the extent of hydrogenation. The product is no longer a fish oil, but a solid or semi-solid white fat free from the original colour and odour. When saponified, it yields a pure white soap, with excellent keeping qualities. As in the manufacture of edible fats, fishoils are usually blended with vegetable and other oils either before or after hydrogenation. By regulating the treatment, fats can be produced that yield soaps of the desired hardness and solubility. The properties of soap from hardened fish oils are obviously very different from those of the soaps of the untreated oil. As the unsaturated acids become saturated, their melting point is raised. Consequently, the solubility of the derived soap is diminished and the emulsifying and other properties changed. The sodium soap from completely hardened fish oil usually contains a large amount of sodium arachidate and sodium behenate, which are soluble only at higher temperatures. This type of soap, therefore, is especially useful for laundry purposes where steam and boiling water are used. Soaps made from vegetable or animal fats are less economical for this purpose because of their high solubility.

SOAPS FROM POLYMERIZED OILS Some interesting results have recently been reported by Hirose (1929) and others workers (Ellis, loco cit.) with regard to soaps made from polymerized fish oils. Instead of saturating the ethenoid linkages of the fatty acids with hydrogen · as in the hardening process, the oil is subjected to prolonged heating in an inert atmosphere such as carbon dioxide. In the treatment the various glyceride molecules become polymerized or joined together through the unsaturated link­ ages, thus giving a structure to the oil, usually making it more viscous and more . stable towards,oxygen. Soaps made from these products are said to be free from:

99. objectionable odour and to possess good keeping qualities. By regulating the degree of polymerization, soaps with lathering qualities almost equal to those of the original oil are said to have been obtained.

SOAPS FROM SULPHONATED FISH OrLs Fish oils and whale oils are used extensively in the sulphonated form (d. page 41) in the preparation of special soaps. In the initial sulphuric acid treat­ ment, some of the unsaturated bonds of the highly unsaturated fatty acids are sulphonated while the greater proportion are polymerized. The sulphonated product is usually saponified by the cold process because the soaps are not easily saltetl out when made by boiling. The most outstanding properties of these soaps are their high solubility and extraordinary emulsifying properties. Being fairly soluble even in brine, they are useful in the preparation of marine soaps for use with sea water. Furthermore, th.ey have the property of holding large amounts of liquid fillers. In Europe partially hydrogenated and sulphonated fish oils and whale oils are used extensively in common household soaps, but on this continent these oils and their soaps find their chief use in industry as emul­ sifying agents for oil-water mixtures.

OTHER SOAPS So far in discussing the properties of soaps, attention has been confined to only two of the large number of soaps, namely, those of potassium and sodium. These are among the commonest of all commodities in daily use. There are, however, others such as ammonium soaps and soaps of iron, copper, lead , mag­ nesium, calcium, nickel, cobalt, manganese, and in fact, every metal that is cap­ able of forming an alkaline hydroxide. Ammonium soaps are compounds of fatty acids and ammonia. They are even softer and more soluble than potassium soaps but decompose slowly with the liberation of ammonia. When mixed with potassium soaps, however, they are more stable. They are used in this form chieflyfor cleansing surgical instruments. Soaps of other metals, unlike those of potassium, sodium and ammonium, are almost insoluble in water and, therefore, are not usually recognized as soap� when met with ordinarily. The preparation of these soaps is easily accomplished. For example, to obtain a magnesium soap, a solution of a magnesium salt is added to a common sodium or potassium soap solution. In the reaction that follows, the magnesium exchanges places with the sodium and itself combines with the fatty acids to give magnesium soaps, which being insoluble, coagulate and precipitate out. This is commonly met with when hard water containing iron, calcium or magnesium salts is used for washing ; the soaps of these metals precipitate as a sticky insol­ uble curd which adheres to the container and the materials in the wash. Soaps of the heavier metals are horny and tough or brittle. The majority of them are completely insoluble in water but fairly soluble in oils. Many soaps of the heavier metals have an important application in industry. I t will be recalled that the soaps of manganese, cobalt and lead and a few other

100 metals, catalyze the oxidation of drying oils. Were it not for these "driers" in paints, varnishes and enamels, the use of these materials for interior decorating would be greatly limited. Copper and other soaps are used widely in anti­ fouling and anti-corrosive paints for ship bottoms, and also as preservatives for fish nets. Still others are important constituents of antiseptics and cosmetics. Fish-oil soaps of lead, calcium and other metals are used chiefly in insecticide spraying emulsions and lubricating greases.

FISH OILS IN PROTECTIVE COATINGS

THE NATURE OF DRYING OIL FILMS As pointed out in previous paragraphs (cf. page 21), all drying oils owe their special properties to certain highly unsaturated fatty acids, namely, linolic acids (C1s -2 unsaturated bonds) , linolenic acids (C1s-3 unsaturated bonds) , elaeos­ tearic acids (isomer* of linolenic acid) and still more highly ·unsaturated members of the C20 and C22 series with three to six double bonds. The first three occur in drying vegetable oils while those of the C20 and C22 series, along with small pro­ portions of linolic adds, are the chief drying components of fish oils. While the above fatty acids are directly responsible for the drying properties of various oils they are not the only factors determining the rate of drying and the characteristics of films. In addition are the following important factors : (1) the kind and proportion of non-drying fatty acids present, and (2) the way these are distributed among the various glycerides. The influence of distribution will be understood from the following types of glycerides.

non-drying fatty acid drying fatty acid Glycerine - non-drying fatty acid Glycerine - non-drying fatty acid [non-drying fatty acid [ non-drying fatty acid 1 2

drying fatty acid drying fatty acid Glycerine - [drying fatty acid Glycerine - drying fatty acid non-drying fatty acid [ . drying fatty acid 3 4

FIGURE 26. Types of glycerides

It is apparent that glycerides of the fourth type will be superior to all others in drying qualities. In the other types, the drying properties will diminish as the number of drying components in the glycerides decreases. The first type shown, of course, possesses no drying qualities. Obviously, then, the drying qualities of an oil containing all four types of glycerides will depend on the proportions of each type present. Some non-drying oils, notably olive oil, contain large pro-

*Isomers or isomerides are chemical compounds which have the same molecular formula but differ in constitution or structure. Elaeostearic acid differs from linolenic acid in the positions of the unsaturated boncl.s in the carbon chain. Similarly, there are different isomers of linolic acid and of the highly unsaturated acids of the C,o and C'2 series. 101 portions (80 per cent. or more) of glycerides of the first type while many drying oils, including poppy seed, China wood and linseed oils, are composed largely of the fourth type. Semi-drying oils such as cottonseed and others contain both drying and non-drying glycerides. The influence of different fatty acids on filmcharacteristics such as hardness, toughness, elasticity, tensile strength, extensibility, water permeability and so forth, is apparent on comparing the films of different oils. China wood oil, for example, is composed largely of simple tri-glycerides (fig. 26, 4) of elaeostearic acid and gives a tough dull film, somewhat lacking in extensibility. The film is especially noteworthy, because of its toughness and low water permeability. Poppyseed oil is composed chieflyof linolic acids and gives a light-coloured trans­ parent filmthat dries hard and becomes brittle. Linseed oil also consists largely of drying glycerides (type 4) but differs from the above oils in that it contains two distinct types of fatty acids-linolic and linolenic-in the same glyceride mole­ cules. This arrangement combines the specific drying properties of both fatty acids and accoun ts for the special properties of linseed oil films. They are trans­ parent, tough and elastic, of good tensile strength and, when new, will withstand considerable elongation. They are also fairly impermeable to moisture. On ageing, however, the filmsbecome harder and more brittle, especially when they contain driers. [Jnder certain extremes of temperatures and on surfaces subject to great expansion and contraction, therefore, they often crack. \"ery little is known about the distribution and arrangement of the fatty acids in the glycerides of fish oils. It has been shown previously that these oils contain fatty acids ranging from saturated members of the C14 series to highly unsaturated acids of the series with as many as six double bonds. The dis­ tribution and arrangement of these in the glycerides is no doubt very but there is reason to believe that of all four sent. and that even after the removal of the most of the solid a considerable proportion of non-drying or components remain in the oil. This partly certain undesirable characteristics of 113h­ oil such as softness, dullness and tackiness. Although these can be cor­ other means, there is no doubt that the qualities of these films would be much improved if the non-drying components could be removed. The chief merits of fish-oilfilms are their flexibility and extensibility. These qualities may be attributed to the highly unsaturated drying fatty acids of the C20 and C22 series, but are no doubt enhanced by the small amounts of linolic acid usually present. Because of these properties, fish-oil films are much less liable to crack and peel on surfaces subject to expansion and contraction than are the more brittle films of linseed oil. \Yhile possessing many valuable qualities, fish-oil films have certain draw­ backs. As previously pointed out, they are some\vhat softer, tackier and less tough than the films of vegetable drying oils. Softness is partly due to the in­ herent nature of the drying components of the films and is a necessary accom-

102 paniment of flexibility : it therefore cannot be considered a total defect. The softness of films, however, is only partly due to this cause. The chief cause of softness and other defects such as lack of toughness and tensile strength in fish-oil (and other oil) films is the presence of non-drying glycerides. These comprise the higher-melting glycerides (types 1 and 2, page 101 which form most of the stearine at ordinary temperatures. As mentioned previously, the bulk of these components can be removed by refrigerating the oil and removing the solids, but the separation is never complete because of the high solubility of these and other non-drying components in the liquid portion. By refrigeration at a lower temperature, more of the undesirable glycerides* may be precipitated and removed.

PROCESSING OF FISH OILS FOR PAINTS Since the preparation of fishoils is similar for the various kinds of protective coatings, a few of the common processes will be outlined before discussing the various fields of application.

REFRIGERATION AND REFI�l"G These processes are described in detail in another section (d. page 72). It ""yill suffice to say, therefore, that fish oils, to be suitable for most protective coating purposes, must be "wintered" or refrigerated and refined to remove the stearine and suspended materials. Oils thus treated give harder, stronger and glossier films and, furthermore, are free from the odour of unrefined oils.

POLY:\ IERIZATIO� OR "BODYI::\G" Fish oils to be used in gloss paints, baking enamels, printing inks, linoleum and other materials, are first "thickened" page or rendered more viscous. The process IS essentially one of and in is commonly

knO\YD as i It D1a y be any one of the methods.

POLY\IEIUZATlON BY HEATING The oldest method consists in heating oil in an open kettle until its vapours on being ignited continue to burn. The container and oil are then removed from the fireand the oil permitted to burn until it reaches the desired thickness. The flameis then extinguished by covering the kettle. This method, as applied to linseed oil, is known as "burning", and is a very old one. It gives a very dark product because of the accumulation of unburned carbon. For this reason, it has been superseded almost entirely by improved methods. To-day, bodied oils of this type are produced by heating raw oils in open or closed kettles over a fire for seyeral hours. If pale oils are desired, the ordinary copper and iron kettles are replaced by aluminum and plated- or enamelled-iron kettles. Heating by means of coils carrying super-heated steam or hot oil

"The glycerides with the highest melting point (and hence the poorest drying qualities) form the greater part of the precipitate each time. 103 instead of direct fire also improves the colour. "Bodied" products of specially pale colour are obtained when oils are heated in vacuo, since this eliminates oxid­ ation and removes volatile products of decomposition. Fish oils, polymerized by these means, correspond to the "stand oils" or "lithographic varnishes" made in the same way from linseed oil. The very viscous products that no longer leave a grease spot on paper, are used in printing inks, lithographic varnishes and baking enamels. The less viscous types may be used in paints and enamels to improve flmving qualities and gloss. Furthermore, being more stable towards oxygen, these oils improve the durability of films.

POLY:vlERIZATION BY BLOWING This treatment involves both polymerization by heat and oxidation by air (oxygen). It consists in blowing air through oil heated to about 100°c:. (212°F.). Sometimes heated air is used and its temperature regulated. \Vithina short time after commencement of the treatment, the rate of oxidation increases very rapidly with liberation of heat. During this period, the temperature is usually controlled by cooling coils or by regulating the air supply. As oxidation proceeds, the oil darkens rapidly and increases in viscosity, and if allowed to proceed to the limit, becomes a plastic rubbery mass. The rate of oxidation and polymerization may be greatly accelerated by the addition of catalysts or "driers" (d. page 22). Oxidation of the oil is accompanied by decomposition. :\I any of the oxid­ ation products being volatile, are driven off by the air ; nevertheless, the final product is usually of high acidity. Being already partly oxidized, it dries readily, but the films are less durable than those from oil polymerized by heat alone. Furthermore, these oils when mixed \vith pigments that do not neutralize the free acidi ty are of ten tacky. Other methods of simultaneously oxidizing and polymerizing oils to the gel state are used in industry, particularly in the manufacture of linoleum. In brief these are as follows : Scrim Oil. Oil containing a drier is allowed to flow down a suspended cotton fabric (scrim) in a room maintained at about 38°C. (100°F.). Because of the large surface exposed, much of the oil dries before it reaches the bottom. That dripping from the fabric is collected and again allowed to flowove r the surface until finally the fabric is coated with a half inch or more of "solidi­ fied" oil. In the process the oil takes up about seven per cent. of its weight of oxygen. The product is used in linoleum as described later. Shower Bath and Smacker Process� Walton. In this process the oil containing driers is allowed to fall continuously in the form of a shower from a tank with a perforated bottom, the temperature of the room being maintained at about 50°C. (122°F.). When the oil becoines too thick to run easily, it is transferred to a steam-jacketed "smacker" in which it is blown intensely with air at 55°C. (131°F.) until it becomes a granular rubbery solid. It is then "stoved" (i.e. heated) for a few days at about 40°C. (104°F.).

104 Taylor Oil. Boiled oil containing lead and manganese is blown ivith air for two or three days at a temperature of about 150°C. (302°F.). The dark product is then divided into smaller lots and heated for six or seven hours at about 250°C. (482°F.) un til the mass solidifies.

SnlULTANEOUS POLY:VlERIZATION AND STEAM DISTILLATION lvlodified Kronstein procedure. This treatment is not used to a great extent in industry. However, the writers have found it of value in the polymerization of drying fish oils. The process consists in maintaining oil at a temperature high enough to cause decomposition (200 to 250°C., 392 to 482°F.) and at the same time steam distilling the decomposition products. The latter, with the steam, are condensed together in the form of a very stable white emulsion. After a time, the residue in the distillation flask suddenly polymerizes to a pale, tough and transparent rubbery mass, extremely sticky and elastic. It consists almost entirely of the more highly unsaturated polymerizable components of the original oil. The nature of the polymerized residue differs with different drying oils but . in every case it shows the chief characteristics of the filmproduc ed by the oil on drying, particularly with regard to elasticity , elongation and toughness. The product from drying fish oils is practically insoluble in most organic solvents but absorbs them readily with great swelling. On prolonged standing or refluxing with certain solvents, such as benzene and xylene, the substance gradually disin­ tegrates and goes into a colloidal solution. vV hen cobalt drier is added to the oil before distillation is started, the final product is dark and, if exposed to air, dries within a few minutes to give a very glossy surface. If dissolved in a solvent and spread on a surface, the resulting films are tough and entirely free from the char­ acteristic tackiness of fish-oil films. The toughness may be improved further by the incorporation of gums.

MISCELLANEOUS METHODS OF POLYMERIZATION Fish oils may be bodied also by any of the following means : Sulphuration -(cf. page 34). vV hen fishoils are heated with sulphur to about 350°C. (662°F.) a violent reaction takes place accompanied by a rapid thickening of the oil and a copious evolution of hydrogen sulphide gas. The latter becomes imprisoned in the thick rubbery material, giving it a sponge-like structure very much like rubber sponge. Polymerized products of this type are important ingredients of lubricating and cooling oils for steel cutting. Fish oils may be polymerized rapidly also by means of sulphur chloride. The reaction commences very slowly at firstbut as heat is liberated the temper­ ature rises rapidly and the reaction takes place with increasing energy. The final rubbery product, like similar products from other highly unsaturated oils, is commonly called iifactice". Condensation by stannous chloride. Certain chemicals such as stannous chloride, amorphous phosphorus, and phenol, facilitate the polymerization of unsaturated bonds on heating. This method, however, is not used commercially to any extent in bodying oils. 105 Ozona/ion. Fish oils blown with ozone* polymerize to give very viscous, pale-coloured and highly-oxidized products. vVhen heated, these oils decompose rapidly \vith considerable charring. Ozonation is used to some extent com­ mercially. Polymerization by ultra-violet radiation. Drying fishoil s may be polymerized and bleached somewhat by exposure to strong ultra-violet light. The process, however, is too slow and costly to be of commercial application.

THE "GSE OF DRIERS AND PIGMENTS BOILED OILS It has been pointed out previously that the rate of drying of oils may be speeded up, and the quality of films improved, by the incorporation of certain metallic salts or "driers". Oils containing these are commonly known as "boiled oils"·t :c\Iethods of preparing these oils differ somewhat with different manufac­ turers but in the main the procedures are the same. In general, the oil is first heated to about 77°e. (207°F.) and maintained at this temperature to drive off moisture. 'When ,frothing ceases, the temperature is raised to about 260°C. (500°F.) to coagulate mucilaginous impurities. The heat is then shut off and driers are added in small amounts at a time with constant stirring until dissolved. To prevent undue darkening the heating is usually done by means of steam coils and the temperature carefully controlled. Boiled oils are usually somewhat higher in viscosity than raw oils because of polymerization during the heat treatment. \\Then to air they dry more rapidly than raw oils and give harder and more'lustrous films.

DRIERS Cobalt and manganese are the hyo most active metallic known for the rate of oxygen absorption and drying of unsaturated oils. Other metals such as cerium, lead, uranium, copper and iron also accelerate oxidation but to a very much smaller These driers are never used in the metallic form although as such, if reduced to a very fine powder, they exert a marked catalytic effect. The follovying compounds of these metals, however, being fairly soluble in oils, are used extensively in industry. (1) Oxides. (2) Soapst�such as linoleates, tungates, resinates. (3) Salts�such as acetates, borates, sulphates, oxalates.

*An ex,tremely active form of oxygen produced by passing an electrical discharge through either air or oxygen. tPrior to the discovery of driers, boiled oils were made by heating linseed oil in contact with air for several hours. tF or example, the cobalt soaps of the fatty acids of linseed oil are known collectively as "cobalt !inoleate"; those of the fatty acids of tung or China wood oil as "cobalt tungate", while corres­ ponding soaps of the fatty acids of rosin are known as "cobalt resinate" or "rosinate". Similarly there are !inoleates, tungates ane! resinates of manganese, lead, etc. 106 The oxides of manganese and lead are commonly used in the preparation of boiled oils and concentrated driers. These products, especially the lead solu­ tions, are usually dark in colour and contain a considerable portion of the oxide in the form of a colloidal suspension. On standing, the coarser particles slowly precipitate out. The metallic soaps are readily soluble in oils and the solutions are very active driers. Concentrated solutions are dark in colour but not as dark as those made from the metallic oxides. The salts of cobalt, manganese, and lead produce very pale driers. As a rule, however, the solubility of these salts in oil is somewhat less than that of the oxides and soaps and the activity of the drier is therefore less. These driers are particularly useful in enamels and clear varnishes where a light-coloured product is desired. 'When lead and manganese oxides are dissolved in linseed oil by heating, large proportions of them combine with the oil to form soaps of the various fatty acids. Some of these soaps become insoluble when the oil is cooled and, after standing for some time, gradually sink to the bottom of the tank to form a brown fatty layer which may be redissolved by heating. A similar action takes place with fish oils, only to a much greater extent. This is due to the higher proportion of glycerides containing solid mono-ethylenic fatty acids that are not removed by refrigeration. All lead driers and even lead pigments cause this precipitation but oxides produce the largest amount. Nlan­ ganese gives less precipitate than lead while cobalt driers give practically none. " Driers" of other metals such as iron, copper, zinc, and aluminum are also used. They are of little importance as accelerators of oxidation but are valuable because of their influence on filmqualit ies.

EFFECT OF DRIERS ON FILM PROPERTIES -While the action of driers in catalyzing oxidation is imperfectly their influence on film qualities is better knovvno As might be expected, the ex­ active driers such as cobalt and manganese, particularly the former, tend to cause surface drying, that is to say, the surface in contact with air dries readily to a skin which hinders the further entrance of oxygen into the interior of the filmo Consequently, the under portion of the film remains liquid for some time after the surface has dried. Such filmsma y easily be "skinned", if rubbed or knocked. \\'hen thoroughly dry, however, they are usually very hard. Manganese driers confer a characteristic pinkish tint to white paints, while the cobalt colour tends to mask the natural yellow colour of the oil and thus improves whitenesso Driers such as cerium, lead, etc., on the other hand, while being less active as accelerators of drying promote uniform drying. Under their influence, liquid oil films thicken gradually and uniformly, finally passing through the gel state into a rubbery film. The last transition takes place fairly rapidly when cerium is present. The films, however, do not dry as hard as those containing cobalt or manganese. Cerium and lead, especially the latter, have a great tendency to

107 combine with solid fatty acids and precipitate out as soaps, thus giving the film a dull appearance and a more tacky surface. The influence of this group of driers is of further use in correcting the ten­ dency of fish-oil and other films to "unspread" or gather into localized areas during drying. This phenomenon, knovvn as "cissing", is not so prevalent in filmsconta ining pigments but the tendency nevertheless may be present and may possibly affect the degree to ,;yohich the oil wets the pigment particles. In oil films alone, particularly ,vhen manganese driers and resinates are used, cissing is very pronounced. It may be corrected, however, by adding very small amounts of cerium or lead driers to the original oil or by polymerizing it to a slight degree. From the above it is evident that the defects of the two groups of driers are somewhat compensating and therefore these driers may be used together with advantage. This is done extensively in the paint industry, manganese and lead being the combination generally used in ordinary paints. Thus, the tendency to surface-dry when cobalt or manganese is present, is corrected by the addition of lead driers. Cobalt is used more extensively in varnishes than in paints. Certain driers such as resinates, tungates and iron Ealts are valuable for hardening fish-oil films. Recalling that fish-oil films are softer than those of linseed oil, it may appear desirable to make use of these hardening agents. Un­ fortunately, however, the quality of flexibility is usually impaired when films are hardened, and therefore hardening agents must be used with discrimination. Resinate driers tend to harden 111ms andmake them brittle. Cobalt tungate has been recommended (Toch 1925) and has been found by the writers to be a desir­ able drier from the standpoint of hardness and water permeability. This drier, however, tends to make films dry dull and greatly increases their tendency to become yellmv in diffused light. From experiments in these laboratories has it been found that cobalt linoleate gives the best results considering the film as a whole. Driers continue to promote oxidation even after the oil film has "dried" throughout. This oxidation, though very slow, gradually brings about the dis­ integration of the film material. The same thing is true of oil films containing no driers, but to a much less degree. From the standpoint of the stability of films to oxidation, therefore, driers should be used as sparingly as possible.

INFLUENCE OF PIGyIENTS ON THE DRYING OF FILMS Pigments also exert a very pronounced influence on the rate of drying and qualities of films. Some act as driers to accelerate the rate of oxidation of oil while others act as retarders. Brown pigments such as siennas and umbers are accelerators, since they contain up to 15 per cent. or more of manganese. Other pigments such as white-lead and certain yellows contain lead, while still others contain large proportions of iron, copper, etc. All these react more or less readily with oils and exert a marked effect on drying. �White-lead (carbonate) and the oxides of lead have an affinity for oil, thus explaining the smooth working quali­ ties of these paints. The accelerating or retarding effect of various pigments controls to a large extent the kind and quantities of driers required. 108 Pigments further influence drying by hindering the diffusion of oxygen from the air into the film. Those of the retarding type and also those of an inert character interfere more with oxygen transfer than pigments of the accelerating or "oxygen-carrying" type. Furthermore, the effect is more pronounced the more finely divided the pigment. A third influenceexerted by pigments, particularly when very finelydiv ided, is the tendency to attract catalytic substances in the oil to their surface, thus reducing their influenceon drying. Admixed with oil, pigments adsorb catalytic substances such as free fatty acids, peroxides, etc., as well as a considerable pro­ portion of the driers present. All pigments have this property to a greater or lesser degree, but certain ones, especially carbon black, silica and other neutral pigments, are extremely active "adsorbent" materials. While the extent and influenceof adsorption is not marked with most pigments it is obviously a factor to be considered in the selection of driers. In addition to their effect on the rate of drying, pigments impart rigidity and hardness to films. The use of hard "pigments" such as silica, etc., as fillers, also enables the film to withstand abrasion. Additional reference to driers is made in a later section (page 132).

FISH OIL PAINTS While it is generally held that fish oils (at least as far as our present knowl­ edge goes) are not suitable by themselves as a vehicle for ordinary paints, their value as adjuncts of linseed oil in special paints is widely recognized. It has been shown that the life of linseed oil paints (under conditions that cause them to crack because of brittleness) is greatly prolonged by the use of drying fish oils. These, as previously pointed out, give flexibility and stretching capacity to films. Paints containing up to 75 per cent. of a good drying fishoil are said to possess excellent durability (Toch 1925). It has been reported also that paints containing a liberal proportion of properly treated fish oil are valuable in localities along the sea coast where the moist atmosphere is especially destructive to films. In addition to imparting flexibility to linseed oil films, drying fish oils also reduce the tendency of the latter to "chalk" with certain pigments such as white­ lead. This defect is due to the disintegration of the surface of the filmliberating the pigment as a fine powder. The phenomenon, while detrimental to protec­ tion, tends to keep the surface bright since adhering dust and dirt are released with the pigment. The use of drying fish oil reduces the tendency to chalk, thereby improving the protective value of the film, but frequently detracting from brightness, because of the dust that remains on the surface. Drying fish oils are useful also for reducing the tendency of certain pigments to "cake" or set hard in the can during storage. Fish oils have been used for many years in the manufacture of heat-resistant paints for boiler fronts and smokestacks. For this purpose they are superior to all other drying oils with the exception of China wood oil. The superior qualities are attributable partly to the high boiling points of the component fatty acids of 109 the C2J and C22 series, but chiefly to the stability of their oxidized polymers. During drying on very hot surfaces, a considerable portion of the lower-boiling constituents, including the non-drying components, is driven off,leaving a hard, tough, residual film. Litharge (lead oxide) is usually incorporated in the oil as a drier and hardener for this purpose. The filmswhen dry are more elastic than those of China wood oil, and consequently more durable. A reference might be made to the reputed "fish odour" which, in the minds of many, is the chief objection to the use of these oils in paints and other com­ modities. Fish oils when fresh and properly refined are pale-coloured products with a characteristic but not an unpleasant odour. This odour is not to be con­ fused with the "putrid fishy odour" characteristic of oils of former days when little care was taken in their production. Such oils are to-day the exception rather than the rule. Like many other oils, however, fish .oils oxidize when exposed to air and liberate pungent aldehydic and other decomposition products that irritate the membranes of the eyes, nose and throat. This is noticeable in an ill-ventilated, freshly-painted room. The odour of oxidizing fish oils can be made less notice­ able by the addition of a small amount of pine oil. Fish oils develop rancidity more rapidly and extensively than do linseed and other less highly unsaturated oils. Consequently, the odour is more pronounced and for this reason fish oils are not so well suited for interior paints. \Vhen dry, however, such paints are odourless.

FLEX�BLE COATINGS Drying fishoils are of value in paints for metal and other surfaces subject to great expansion and contraction. They are generally used along with linseed oil to impart flexibility and extensibility to films, thus diminishing the tendency to crack and peel. Similarly, in paints for cloth and other flexible materials subject to folding, drying fish oils impart the necessary flexibility.

PATE�T LEATHER, ENAMELLED LEATHER The enamel used for these purposes consists usually of polymerized boiled linseed oil containing suitable driers, usually lead, manganese, Prussian blue (hardener) and suitable pigments. The preparation of the enamel and the con­ ditions of its application depend on the nature of the product desired. Usually three coats are applied, each being dried under special conditions. After the third coat is dry, the product is exposed to the sun or ultra-violet radiation for several hours to make the coating more flexible. Drying fish oils have been used to a small extent in enamelled coatings for leather and have been found satisfactory except for the tendency to develop a dull whitish coating or "bloom" on the surface. The bloom may be removed by wiping the surface with a solvent but it reappears in the course of a few days. Consequently, these oils are only used in coatings that are to be polished fre­ quently. Cellulose lacquers are being used to an increasing extent in this field to replace oil coatings. 110 Blooming is not peculiar to fish oil filmsalone but is usually more pronounced when these oils are present. The writers have observed that when refrigerated fish oils are baked, the films are free from bloom, but if driers are added, or if polymerized oils are baked with or without driers, blooming is quite pronounced. The bloom itself consists of countless numbers of microscopic crystals, presumably solid free fatty acids which gradually emerge from the interior of the film. These are beautifully iridescent when viewed through the microscope. They usually melt between 45 and 55°C. (113 and 131°F.) and are volatilized at temperatures above 200°C. (392° F.).

OILED FABRICS These include materials such as used in raincoats, tarpaulin, "American" cloth, table baize, etc. They are manufactured by applying several coats of boiled oil containing suitable pigments and allowing each coat to dry thoroughly. Here again drying fish oils are· used extensively for imparting flexibility to the coating.

LINOLEUyl, FLOORCLOTH In the manufacture of these products, oil containing driers is oxidized and polymerized to the solid rubbery state by various methods (d. page 104). The product is then thoroughly ground and kneaded with powdered cork, gums, pig­ ments and fillers, and the resulting plastic mass pressed in a uniform layer on to a jute canvas backing by means of a series of steam-heated rollers. After cooling, the canvas surface is given a coating of paint containing varnish gums and pig­ ments, which solidifies on cooling. The linoleum thus produced is finally stoved or "seasoned" for two or three weeks in rooms at about 23°C. (73°F.). Drying fish oils are used extensively on this continent along with linseed oil in the manufacture of these commodities, the product being more flexible than that from linseed oil alone.

FISH OILS IN TANNING The annual consumption of fish oils in the leather industries on this con­ tinent is in the neighbourhood of 8,000 tons. These oils are used for two purposes :

FAT-STUFFING AND FAT-LIQUORING Hides freshly tanned with bark or synthetic tanning materials are porous, stiff andbri ttle. To render them soft and flexible, therefore, they are impreg­ nated with greases and other fatty mixtures. The manner of treatment depends on the nature of the desired product. If the finished leather is to contain more than 20 per cent. of grease, the hide is usually "stuffed", that is, the grease is worked or "drummed" in by hand or machines. If a lower fat content is desired, the raw hide, either in a wet or dry condition as the case may require, is "fat­ liquored" with an emulsion of oil and water. As the water evaporates, the oil penetrates into the leather, leaving the surface dry and non-oily. Fats and oils incorporated into hides by these methods not only lubricate the fibres, imparting flexibility to the product, but also render it waterproof by fillingthe pores. 111 Mixtures used for stuffing and liquoring consist largely of "degras" from chamois tanning, compounded with tallow, fish stearine, bone fat and other greases. Blown whale oil, and raw and sulphonated fishoils, are also used exten­ sively in certain mixtures. Sulphonated fish oils are employed chiefly as an emulsifying agent for fat-liquoring emulsions.

CHAMOIS TANNING

For this type of work drying fish oils are used exclusively. Here they serye not simply as lubricating and softening agents but as the active material in the tanning process. Briefly stated, the process is as follows : The "splits" (layer of skin nearest the flesh) of sheep or goat skins after "bating" (a type of fermentation or curing) are fastened in a machine known as the "stocks" and subjected to an intensive beating (" pummelling") during which time they are thoroughly impregnated ("fulled") with a drying fish oil free of stearine. The stocking treatment is stopped periodically and the skins spread out to cool. \Vhen thoroughly saturated with oil they may be packed in boxes, heaped loosely on the Hoor or hung up in a room maintained at about 37°C. (100°F.). If packed, they develop a moderate heat due to oxidation of the oil and the adsorption of oxidized products on the fibresur faces of the leather. The temperature during this "staving" process is not allowed to exceed 54°C, (130°F.). If, after the first stoving, tanning is not complete, a further stocking may be necessary, followed by additional stoving. Finally, when heating has subsided, the flexible and soft yellow hides are soaked in VFarm water and placed in a hydraulic press to remove the excess oil and water. The liquids come from the press as an emulsion known as "degras", which can be used again for stuffing and fat-liquoring purposes, or may be sold to the soap manufacturer. The free oil still remaining in the skins is saponified by washing with a solution of sodium carbonate and removed by pressing. The hides are finally dried, worked until soft, bleached and buffed, yielding a finished product that is very soft and open. A tanning process somewhat similar to that described above is used in oil tanning buckskin, mocha and other soft leathers. The tanning action of drying fishoils is imperfectly understood. It has been suggested that certain of the peroxides formed on oxidation may combine with the amino groups of the collagen of the skin, while other peroxides may remain unchanged, or pass through the hydroxy stage, finally condensing to a stable lactone ring structure. It has also been suggested that the aldehydic products of oxidation may exert a tanning action similar to that of formaldehyde. To explain the superiority of drying fishoils over yegetable oils for chamois tanning, it has been suggested, furthermore, that the individual highly unsaturated fatty acids of fishoi ls, because of the number of unsaturated bonds (3 to 6) , may par­ ticipate simultaneously in many diverse reactions, as for example, the formation of peroxides, lactone ring structures, union with collagen, polymerised structures and so forth. The drying fatty acids of vegetable oils, as will be recalled, contain only up to three unsaturated bonds. 112 Menhaden and cod oils have been used on this continent for many decades in the currying of leather, the former still being used extensively. Within later years, however, other oils including whale, herring, salmon, sardine and pilchard, have also come into prominence in this industry. For chamois tanning, men­ haden, pilchard, and sardine oils are particularly valuable because of their re­ markable drying qualities.

FISH OILS IN LUBRICATION

PROPERTIES OF LUBRICATING OILS When two surfaces are made to slide over each other the motion is resisted by a force called friction. This friction is due to the interlocking of minute irregularities in the surfaces and also to the adhesion of the parts in close contact. The purpose of lubrication is to reduce this friction, and it is accomplished by putting a third substance (the lubricant) between the sliding surfaces. The nature of this lubricant is very important. Most of them are liquids, but all liquids are not lubricants. For example, water increases the friction between two glass surfaces but reduces the friction between ebony surfaces. In industry, practically all moving parts requiring lubrication are made of metal and it has been found that mineral and fatty oils are the most efficient lubricants for this purpose. Among the properties that a good lubricant should possess, the fol­ lowing are the most important. Oiliness may be defined as the power of a lubricant to maintain a film between two surfaces even when under heavy loads. Oiliness depends more on the chemical nature of the lubricant than it does upon the physical, and it appears to be due to the action of the lubricant on the surface. The wetting power of an oil is a measure of its oiliness. Oils that wet metal surfaces are better lubricants than those that do not. Animal and vegetable oils possess this property to a higher degree than mineral oils. Chemical stability is of great importance in lubricants, particularly where high temperatures are encountered. Oxidation of mineral and fatty oil causes gumming and the products of oxidation are acidic in nature, thus causing damage to the lubricated metal parts. Mineral oils are more stable towards oxidation than are the fatty oils. Viscosity of a lubricant should be high enough to maintain an unbroken film between the lubricated parts, but it should not be too high, as high viscosity oils have a frictional resistance within themselves. Viscosity is not quite so important a property as was once thought, since the maintenance of a con­ tinuous film is more a function of the oiliness of the lubricant than of vis­ cosity. Mineral and fatty oils can be obtained over a large range of vis­ cosities. Uniform consistency at different temperatures. When any oil is heated (so long as there is no chemical change) its viscosity decreases and, conversely, when cooled, the viscosity, increases. If the viscosity of the oil becomes very low, a continuous film may not be maintained, particularly if the oiliness is low

113 8 too, while if the viscosity rises too high, the frictional resistance of the oil will prevent proper lubrication. Increase of pressure also increases viscosity. Both temperature and pressure affect the viscosity of mineral oils to a far greater extent than that of fatty oils. Freedom from corrosive acids. Lubricating oils should be of neutral reaction or, if slightly acid, should not corrode the metal parts to which they are applied. Oils which oxidize and gum produce acidic by-products which have a cor­ rosive action. Small amounts of free fatty acids have been shown to be harmless (see below). j11inimum coefficient of friction is required in lubricating oils. Furthermore, it has been shown that fatty oils with small amounts of free fatty acids have still lower coefficients than those of neutral oils. The coefficients of mineral oils can be reduced by blending with fatty oils or by the addition of small amounts of free fatty acids. Low cost is essential in lubricating oils. Mineral oils, as a class, are more suitable as lubricants. They are cheaper and have no other widespread use. Many of their faults can be corrected by the admixture of small amounts of fatty oils. On the other hand, fatty oils, as a class, are far too valuable for other purposes to be generally used as lubricants. Furthermore, their relative instability limits their usefulness in this field. From the above summary of the properties of lubricants, some idea of the relative values of mineral and fatty oils can be obtained. While mineral oils are in general use as lubricants, there are certain specialized fieldsin which fatty oils are particularly valuable. The application of fish oils to lubrication, therefore, can now be discussed.

SPINDLE OR LIGHT OILS, AND NON-BLENDED OILS Oils of these kinds are used in liquid-oil film lubrication, in which the sur­ faces being lubricated have to be continuously wet by the lubricant (in contra­ distinction to lubrication such as used in gears, etc.). The finer oils with the greatest oiliness and the lowest viscosity are used for the lubrication of clocks, watches, aeronautical instruments and very fine machinery. More viscous, heavier, fatty oils are used for the lubrication of textile looms, and for high-speed engines very viscous, fatty oils have been found to be suitable. For the lubrication of watches and other delicate instruments, the oil from the head and jaw of the porpoise and blackfish have been found to be excellent. These oils combine the properties of great oiliness, low viscosity and chemical stability, and in addition they remain fluid at very low temperatures. The market value of these oils has risen greatly in the last few years and they are now selling at approximately one hundred dollars a gallon. They are very scarce. This is because there is little porpoise fishingcarried on and also because the yield of oil from each porpoise is very small (see V. Nabell 1927; Anon 1929 ; Sunder­ land 1932, etc.). The Clock Manufacturers' Association of America, in co­ operation with the United States Bureau of Standards, has commenced an inves- 114 tigation into the possibility of either increasing the supply of porpoise jaw oil or so treating other oils that they may be used for the same purpose (Tech. News Bull. No. 172). Castor oil, either alone or blown and blended with mineral oils, is used to a great extent in high-speed engines, automobile racing engines, etc. For purposes where castor oil has proven satisfactory it is suggested that certain fish-liver oils might possibly be used to advantage. Technical fish-liver oils are of greater value for lubricating purposes than fish-body oils because they are less highly . unsaturated, contain less stearine and are less susceptible to oxidation. Thus they do not "gum" so readily and remain fluid to lower temperatures. Among these liver oils special mention should be made (for economic as well as tech­ nological reasons) of ratfish-liver and greyfish-liver oils. The former is a light yellow liquid that remains clear to _Soc. (26.6°F.). It has a low iodine value (d. page 147) and contains large quantities of unsaponifiable matter. It wets metal readily, particularly when a trace (less than 0.5 per cent.) of free fatty acids is present. A few of the physical properties of rat-fish liver oil are given in table XVI. TABLE XVI.-Physical characteristics of rat-fish liver oil Specific gravity at 25°C ...... 0.8991

Clouding point ...... _3°C.

Solidification point .....'. ' ...... _12°C.

Viscosity at in: poises ...... 1.31 lOoC. Viscosity at 25°C. in poises ...... 0.63

Viscosity at 50°C. in poises ...... , ...... 0.36 Visr;osity at 65°C. in poises ...... 0.32 The liver oil of the greyfish is also of some interest from the standpoint of lubri­ cation. It is more highly unsaturated than ratfish oil (d. page 143), contains smaller amounts of unsaponifiable matter and if properly processed does not readily oxidize. BLENDED OILS Fatty oils, with the exception of castor oil, are soluble in all proportions of mineral oils, and for general purposes a blend of the two classes of oils is com­ monly used. Such blended oils are used for·the lubrication of internal combustion engines, gas engines, steam engines, etc. Raw or blown rapeseed and castor oils are used to a great extent for this purpose but the use of other oils with similar properties is becoming more general. Olive oil is used and is highly recommended for tractor and automobile engines. Oleo and coconut oils have also been used for blending with mineral oils for use in gas engines. For blending purposes fish-liver oils of low iodine value and low stearine content deserve serious consideration. They are relatively cheap, can be ob­ tained in large quantities and, if properly processed, can be made quite stable to oxidation. They are much superior to blown vegetable oils.

GREASES AND SOLID LUBRICANTS These lubricants are usually used for railway-coach axles, stuffing boxes, crank-pins, etc. They contain considerable amounts of fatty oils. They may 115 consist of: mixtures of fats compounded with mineral oils; fatty oils alone; emulsions of fat and soap, with or wi thou t mineral oils; emulsions of rosin soaps and fatty or mineral oil; mixtures of soap, fatty or mineral oils and solid lubri­ cants such as graphite, etc. The soaps used are usually those of calcium, sodium, potassium or lead. A great many differentformula e are used in the manufacture of the various kinds of solid lubricants but they all contain fatty oils, either free or combined as soap. These oils usually consist of various tallows, hydrogenated fish or whale oil and others. Fish stearine is also used for this purpose. Any low-grade fishoil can be used provided that it is first hardened by hydrogenation.

CUTTING OILS Fish oils have an important application in lubricating and cooling oils used in the machining of metals. For certain types of lubricating mixtures they are used in the raw state, blended with other animal and mineral oils, while for others they are first sulphurized or sulphonated. Lubricants for heavy-duty cutting and finishingwork usually consist of sulphurized fishoils dissolved in mineral oils and blended with animal fats and oils. In certain types of cutting and cooling oils, degras from the leather industry and sulphonated fishoils are used, the latter being especially valuable for producing emulsions. The introduction and im­ provement of sulphurized and sulphonated fishoils for steel-cutting has meant a great deal to the industry by speeding up the output of machine shops and pro­ longing the life of cutting tools.

THE PROCESSING OF FISH OILS FOR LUBRICATING PURPOSES Most fish oils in their raw state are unsuitable as lubricants. This is espe­ cially true of the highly unsaturated fish-bodyoils. Fish-liver oils can be im­ proved by simple processes that reduce their tendency to oxidize and gum. A preliminary study of this subject has been made in these laboratories and of the various methods investigated the following four have warranted further study.

POLYMERIZATION Fish-body oils can be bodied by heating in vacuo and can be made very viscous without darkening the colour or increasing the free acidity. This treat­ ment reduces the tendency of the oil to oxidize and gum but does not entirely eliminate it. Fish-liver oils, such as greyfish-liver oil and ratfish-liveroil do not "body" to the same degree but they can be made highly resistant to oxidation by such polymerization. Heat-bodied fish-body and liver oils are suitable for the mailUfacture of blended oils. Bodied oils made by the blowing process are sometimes used for the manu­ facture of blended lubricants. Blown fish oils are not to be recommended for this purpose, because, like other blown fatty oils, they oxidize readily and their tendency to gum is not eliminated.

HYDROXYLATION It has been found (W. B. Hardy 1919) that the lubricating properties of a substance increases with the addition of a single alcohol or hydroxyl group (d.

116 page 14). The hydroxylation of greyfish-liver oil was therefore attempted (Brocklesby and Tipson 1929) with the object of increasing the viscosity and lubricating properties. It has been found that the viscosity can be increased but up to the present the process has only been carried out on small quantities and the lubricating properties of the hydroxylated oil have yet to be investigated.

HYDROGENATION This process has already been described in some detail. If fish oils are hydrogenated for a very short time only, the highly unsaturated fatty acids become saturated and the tendency of the oil to oxidize and gum is greatly re­ duced. This process of partial hydrogenation is particularly effectivewith fish­ liver oils which are not highly unsaturated. Very stable oils can be produced. Close control has to be maintained over the process, however, in order that solid fats are not formed. Completely hardened fish oils may be used in greases as mentioned above.

ANTI -OXIDANTS The use of anti-oxidants has already been mentioned in page 23. Their application is particularly effective in the case of lubricating oils. Pyrogallol and hydroquinone are among the most efficientof these, although tetra-ethyl lead has also been used for the prevention of oxidation of lubricants. These substances greatly retard the oxidation of such highly unsaturated fish oils as pilchard oil (figure 4) and practically stop oxidation of greyfish-liver oil. (A sample of grey­ fish-liver oil to which had been added one-twentieth of one per cent. of hydro­ quinone abwrbed in three months' time one-third of the amount of oxygen that was absorbed in two weeks by an equal weight of the oil without addition of hydroquinone.) The above methods have been studied only from the standpoint of increase in viscosity and elimination of oxidation. No tests have yet been carried out on these oils under actual lubricating conditions.

MISCELLANEOUS USES

PRINTING INKS AND LITHOGRAPHIC VARNISHES Printing inks consist of suitable pigments ground in a varnish medium of polymerized oil mixed with rosin oil, rosin and sometimes mineral oil. The polymerized oil is usually prepared by heating linseed or fish oils in a covered kettle until a drop of the oil placed on paper no longer leaves a grease spot. Soap is usually incorporated in the ink to make it "lift" well, that is, to make it leave the type readily in the printing process. Mineral oils also are used for this purpose. Fish oils are used in the manufacture of certain printing inks, the annual consumption being in the neighbourhood of fifty thousand pounds. Lithographic varnishes are similar to printing inks but usually contain oils of much higher body together with a greater proportion of pigments and gums.

117 TIN AND TERNE PLATE Fats are used in the manufacture of tin plate to prevent oxidation of the surface of the molten tin in the pot and of the plated sheets as they emerge from the bath. The molten tin is covered with a layer of oil (melted fat) about 15 inches deep and the temperature of the bath kept about 315°C. (600°F.). The temperature of the oil near the surface is usually about 250°C. (480°F.). Fats used for this purpose must be relatively stable to heat and oxidation. Otherwise they are easily volatilized or decomposed, and furthermore, they tend to polymerize rapidly at the temperatures used. When this occurs, the oil loses its power to keep the plated surface clean. Palm oil is still the principal oil used in this industry but hardened cottonseed and fishoils have also proven very satisfactory (Collins and Clarke 1920). Being of higher melting point, they (particularly the hardened fish oil) stand much higher temperatures than does palm oil, and consequently undergo much less decomposition.

REFERENCES

BOGUE, R. H. Colloidal behaviour. McGraw-Hill, New York. 1924. BRONSON, B. S. Nutrition and food chemistry. J. Wiley, New York. 1930. CAMERON, A. T. A textbook of biochemistry. 3rd Ed. Churchill, London. 1931. CLAYTON, W. The theory of emulsions and emulsification. Blakiston, Phila- delphia. 1923. ELLIS, C. Hydrogenation of organic substances. 3rd Ed. Van Nostrand, New York. 1930. GARDNER, H. A. Physical and chemical examination of paints, varnishes, lacquers and colours. Institute of Paint and Varnish, \Vashington, D.C. 1927. HEATON, N. Outlines of paint technology. Lippincott, London. 1928. HILDITCH, T. P. (loc. cit.). 1927. HOLMES, H. Colloid symposium monograph. J. Wiley & Sons, New York. 1925. MARTIN, G· Industrial and manufacturing chemistry. Crosby, Lockwood & Son, London. 1925. MORRELL, R. S. AND H. R. WOOD. The chemistry of drying oils. D. van Nostrand Co., New York. 1925. MORRELL, R. S. Varnishes and their components. Hodder & Stoughton, London. 1923. MITCHELL, C. A. (loc. cit.). 1918. PEARSON, H. P. Waterproofing textile fabrics. Chemical Catalog Co., New York. 1924. ROGERS, A. Manual of industrial chemistry. 4th Ed. D. Van Nostrand, New York. 1926. TAYLOR, H. S. A treatise on physical chemistry. D. van Nostrand, New York. 1925.

118 THORPE, SIR EDWARD. A dictionary of applied chemistry. Longmans Green & CO., London. 1927. TOCH, M. Chemistry and technology of paints. D. van Nostrand, New York. 1925. TRESSLER, D. K. Marine products of commerce. Chemical Catalog Co., New York. 1923. \VILSON, J. R. The chemistry of leather manufacture. Chemical Catalog Co., New York. 1923. FOODS

LANGWORTHY, C. F. The digestibility of fats. J. Ind. Eng. Chem. 15, 3 (276- 278). 1923. McCoy, J. M. The determination of the smoking point of fats. Ind. Eng. Chem., Anal . Ed. 3, 4 (347-348). 1931. PLATT, vV.AND R. S. FLEMING. The action of shortening in the light of the new theories of surface phenomena. Ind. Eng. Chem. 15, 4 (390). 1923. PLATT, W. AND R. S. FLEMING. Digestibility of some hardened oils. Am. J. Physiol. 54, 479. 1921. MEDICINAL

ASMUNDSON, V. S., Vv. J. ALLARDYCE, J. BIELY. "Fish oils as sources of vitamin D for poultry". Scient. Agric. Vol. ix, No. 9, May. 1929. BAILEY, B. E. "Vitamin D potency of canned salmon". BioI. Bd. of Canada, Prog. Repts. Pacific No. 13, 13. 1932. BILLS, C. E. "Antirachitic substances. VI. The distribution of vitamin D". J.B.C. lxxii, 751. 1927. BIOLOGICAL LABORATORIES, CALIFORNIA PACKING CORP . Private communi- cation. 1931. BROCKLESBY, H, N. "Determination of vitamin A content in liver oil of the dogfish Squalus suckIii". Can. Chem. Met., Sept. 1927. BROCKLESBY, H. N. "Vitamin D content of liver oil of the dogfish". Can. Chem. Met. March. 1929. BROCKLESBY, H. N. AND O. F. DENSTEDT. "The nutritive value of marine products. III. Vitamin D content of commercial pilchard oil". Can. Chem. Met. January. 1930. DEPT. OF AGRICULTURE, DOMINION EXPERIMENTAL FARMS. Private communi- cation. Vitamin A in pilchard oil. 1932. FINN, D. B. "Nutritive value of marine products. IV. Notes on vitamin A content of commercial pilchard oil. Cont. Can. BioI. Fish., Vol. vi, No. 13. 1931. HESS, A. F. AND M . \VIENSTOCK. "Puffer fish oil" . Proc. Soc. Exp. Biol. Med. xxiii, p. 407. 1927. HOLMES, A. D. "Studies of vitamin potency of cod-liver oil". VII. Vitamin A potency of hake liver oil. Ind. Eng. Chem., Apr. 1924, p. 379. VIII. Potency of haddock liver oil. J. Met. Res., Vol. 5, Nos. 4, 5, 6. 1924. 119 HOLMES, A. D. AND M. G. PIGGOTT. "Studies of vitamin potency of cod-liver oils. XVII. Vitamin potency of salmon body oil". Boston Med. Surg. J. Vol. 193, No. 16, p. 726. 1925. MANNING, J. R. "Bibliography on cod-liver oil in animal feeding". U.s. Bureau of Fisheries Doc. No. 1065. 1929. NELSON, E. M. AND J. R. MANNING. "Vitamins A and D in fish oils". Ind. Eng. Chem., Dec. 1930, p. 1361. 1930. SCHMIDT-NIELSEN, S. AND S. SCHMIDT-NIELSEN. "Some liver oils yielding strong colour reactions with antimony trichloride". Biochem. J. 23, 1153. 1929.

SOAP FALL, P. H. "Detergent action of soaps". J. Phys. Chem. 31 (801-49). (Through J.S. C.I. 46, 38, (727) , 1927. 1927. HIROSE, "Soap from polymerized fish oil". J. Soc. Chem. Ind. Japan, 32 M. (381-4). 1929. TSUJIMOTO, M. "Cause of odour of oils and fats, especially of marine animal oils". C.A. 3 (1223). 909. 1 ELLIS, C. "Hydrogenation of organic substances". 3rd Ed. (453-6). D. Van Nostrand Co., New York. 1930.

PROTECTIVE COATINGS KRONSTEIN, A. Zeut. angew. Chem. 34 (68). 1921. Lewkowitsch and Warburton, Vol. III. 131. 1921.

LEATHER SCHLOSSTEIN, H. Fish oils and the leather industry. J. Leather Chem. Assoc. 14, 41. 1919. LUBRICANTS A D' RCAMBAL, A. H. Machinability of metals. Can. Chem. lvIet. xv, 10, 270. 1931. 1928. THORPE, E. A dictionary of applied chemistry. Vol. iv. London. HILDITCH, T. P. The industrial chemistry of fats and waxes. New York. 1927. STILLMAN, T. B. The examination of lubricating oils. New York. BRUNNER, R. The manufacture of lubricants, shoe polishes, and leather dress­ ings. Translated from the German by H. Stocks. ANON. The porpoise industry in Russia. Chem. Umschau, 34, 219. 1927. ANON. Lubrication of clocks and fine mechanisms. Technical News Bull. 172, 86. U.S. Dept. of Commerce. (Bureau of Standards) . 1931. BROCKLESBY, H. N. AND R. S. TIPSON. The hydroxylation of greyfish liver oil. Unpublished MSS. 1929. CHAMPSAUR, N. The use of olive oil for the lubrication of tractor motors. Ann. Combustibles Liquids, through C.A . 25, 4392. 1931. HARDY, W. B. AND H. K. Theories of lubrication. C.A . 13, 2805. 1919. KAY, W. Mineral oils in lubrication. J. Soc. Chem. Ind. 691. 1931. 120 NABEIL, Oils from the head of a porpoise. Chem. Umschau ,2 8. 1927. V. 34 1 SUNDERLAND, P. A. The oil of the north Pacific porpoise. Prog. Reports (Pa- cific) No. 14. 1932. WELLS, H. M. AND J. E. SOUTHCOMBE. The theory and practice of lubrication. Petroleum Times, 3, 173 and 201. 1920.

TIN PLATE

COLLINS, W. D. AND CLARKE. The use of hydrogenated oils)n the manufacture of tin plate. Ind. Eng. Chem. 12, 2 (149-152). 1920.

121

SECTION VI

FISH OILS OF BRITISH COLUMBIA

PILCHARD OIL The British Columbia pilchard is a small fishwh ich appears in large numbers offthe west coast of Vancouver Island. It is a member of the sardine family and in many respects resembles the herring but is much oilier. The amount of oil varies with the season. During the earlier part of the summer the yield averages about 25 gallons to the ton (12 per cent.) but towards the fall it increases to as high ai 50 gallons (25 per cent.). Pilchards are used almost exclusively for the production of fish meal and oil. " Since its commencement in 1925 ihe pilchard industry has grown rapidly. Some idea of its size may be obtained from the "Fisheries Statistics of Canada" for 1929 from which the data in table XVII are taken. TABLE XVII.-1929 statistics of pilchard oil and meal industry

Number of plants operating ...... ; . .... 21 Capital investment ...... $2,315,237 Number of employees (in plants) ...... 438 Salary and wages of employees ...... $380,294 . Fuel used ...... $65,580

Value of fish used ...... '...... $584,469 Other materials used ...... $44,398 Quantity of pilchard meal in tons ...... 15,826 Value of pilchard meal ...... $658,867 Quantity of pilchard oil in gallons ...... 2,856,579

Value of pilchard oil ...... $1,128,164 It will be realized that this branch of the fishing industry is indeed an important one. Quoting from "Fisheries Statistics of Canada" it is learned that, "In 1929 the pilchard was third on the list of principal kinds of fishes in British Columbia in order of value, and seventh on the list of the chief commercial fishes for the whole of Canada". Since approximately two thirds of the value of the pilchard rests in the oil, it is of great interest to consider some of the properties of this substance. Pilchard oil has a light red-brown colour but in the fall may have a decided greenish tint. The greenish colour is stable in diffused light but disappears when exposed to direct light. Figure 27 shows the absorption spectra of two samples of an originally green-tinted oil. Sample i was exposed to the sun­ light for a day and sample 2 was kept in the dark. It will be noticed that in addition to absorbing the blue part of the spectrum more sharply the sample kept in the dark has a well-defined absorption band in the red (6.55 to 6.75X 10-5 ems. *). This band disappears when the oil is exposed to sunlight but *It is interesting to note that chlorophyll has a very strong absorption band at 6.55-6.2'9 X 10-5 ems. It is possible that the green colour in the oils consists of chlorophyll from the green marine algae ("green feed") upon which pilchards sometimes feed. 125 may be reproduced after a further period in the dark. This interesting photo­ chemical phenomenon is exhibited by raw pilchard oils and retained by those which have been polymerized by heat in the absence of air. The greenish tint is permanently removed, however, by oxidation, hydrogenation or decolorization with activated earths.

No rmal Sp ecfrum

Somple No .1 Exp osed to li9hf(yellow Sample No. 2 Kepf in dark(jreenish

FIGURE 22. Absorption spectra of pilchard oil.

In table XVIII given below will be found a few of the more important analytical characteristics of pilchard oil.

TABLE XVIII.-Characteristics of British Columbia pilchard oil Colour in Lovibond units (1 cm. cell) ...... 20 .0 Y 1.2 R Specific gravity at 25°C. " ...... 0.9140-0 . 9209 Refractive index at 25°C...... 1.4785 at 40°C...... 1.4732

Coefficient of expansion ...... 0.00075 cc. per cc. per 0C.

Viscosity at 25°C...... 0.46 poises Acid value ...... 0.2-5.2 Saponification value ...... 193-199 Iodine value ...... 173-183

Unsaponifiable matter ...... � ...... 0.1-0 .3%

CHARACTERISTICS OF FATTY ACIDS

Melting point ...... 32°C.

Saponification equivalent ...... 281-283 Iodine value ...... 185-188 Chloroform 28 . 4-32 .9% Brominat d fatty acids in- � Ethyl ether ...... 38. 8-43 .6% soluble Ill, : 1 Petroleum ether 77 . 2-92 .9%

Oxidized fatty acids ...... = nil to 2.1%

The oil is highly unsaturated and readily absorbs oxygen from the air. In spite of its highly unsaturated character however, it deposits a fair amount of stearine at ordinary temperatures. The stearine is usually of a lighter colour than the oil. It is unsaturated, the ambunt of unsaturation depending on the temperature at which it is precipitated. The commercial oil is also very low in nitrogenous material, an average value of 0.004 per cent. being obtained for a large number of 126 determinatioI1s. This amount can be reduced by filtration or refining as it is partly due to suspended matter. The free fatty acids of pilchard oil have the general characteristics as shown in the above table. From the results of an investigation carried out in these laboratories it is possible to make the following observations concerning the composition of these acids. The saturated fatty acid content is approximately 25 per cent. of the total. This saturated fatty-acid mixture has approximately the following composition : myristic acid ...... trace to 2% palmitic ...... 70 % stearic ...... 26% arachidic ...... 2% behenic ...... trace The unsaturated fatty acids, constituting about 75 per cent. of the total fatty acids were separated into a highly and less highly unsaturated portions with results as shown in table XIX.

TABLE XIX.-Characteristics of unsaturated fatty acids in pilchard oil

Less highly H ighly Fraction unsaturated unsaturated Per cent. of total fatty acids . 39 36 Iodine value ...... 147.8 302 5 Molecular weight .. 290.2 315.8 By fractional distillation of the methyl esters of these fatty acids it was found that unsaturated acids with from one to five double bonds and from the C14 to C22 series were present. A considerable amount of mono- and di-ethylenic fatty acids of the CIS to C22 series was found. Clupanodonic acid was found to be present as well as tri- and tetra-ethylenic acids of high molecular weight. It is not possible to discuss this subject further at this time but it may be pointed out in general that the fatty acids of pilchard oil approximate those of menhaden and J ap fish oil shown in table V. The pilchard oil produced in British Columbia during the last three years has been of a remarkably uniform grade. The following analyses (table XX) made on large bulk shipments, show the low acidity and general freedom from impurities. TABLE XX.-Average analyses of pilchard oil

Amount represented Free fatty Ether Season by sample acids Moisture inso!. (long tons) (as oleic) impurities

- . .. 0 -: -. . � .-. - ---�-�-6 ----�-' �-�-----�-�;� ---I ---OT �;C� -- 11930..:� -: -_-- 606 0.64 026% i 002% I����: I 127 From the analysis of 56 parcels assembled for bulk shipment in 1928, it was found that the highest free fatty acid content was 2.15 per cent. with an average of 0.84 per cent. In only 15 cases did the acidity reach as high as I-per cent. In 8 samples only did the moisture reach 1 per cent. while only 4 had 0.1 per cent., or over of insoluble matter. Since this bulk shipment represented about one quarter of the entire production these values are a fair indication of the uniform high quality of the oil. In an effortto establish the seasonal variation in character of the oil, samples were obtained from one plant at intervals during a season's run. In table XXI are given some of the data obtained. TABLE XX I.-Analysis samples pilchard oil received from one plant during 1929 season Yield in I Refractive Sample Date gals. per ! index Iodine Sapon. Acid Specific number processed ton at 25° values values value gravity ------! 1. . • > •• July 2/29 32 I 1.4785 173.2 194.8 I 1.10 0.9140 2 . ... Aug. 2/29 40 1.4786 177 3 195.2 0.76 0.9144 4...... Aug. 9/29 i 40 1.4784 I 179.3 196.1 5.21 0.9146 ' . Aug. 5 . . . . 16/29 45 1.4789 180.3 195 6 I 1 43 0.9147 Aug. . . 6. 16/29 43 1 . 4790 181. 9 193.5 I 3.43 0.9146 7. Sept. 3/29 40 1 . 4792 I 183.2 194.0 .79 0.9148 8. . . . Sept. 15/29 43 I 1 . 4792 183.4 198.8 2.12 0.9150 3. .. Oct. 7/29 50 1.4790 182.3 196.5 0.88 0.9152 I II I I I I The most important thing shownI by this table is the gradually increasing degree of unsaturation of the oil. This is of importance to buyers interested in the drying properties of pilchard oil since a difference of 10 in the iodine value indicates a higher proportion of the drying components. It has also been noted that the samples with the objectionable odours were those with the greener shades. Since it has been found that fishf eeding on "green feed" are difficult to process, the relationship is obvious. Of the physical properties of pilchard oil probably the two most important are the specific gravity and the precipitation of stearine. From the industrial standpoint it is important to know the change in specific gravity with change of temperature. Different samples of pilchard oil, at any one temperature differ in specific gravity over a small range. Specific gravities were determined by means of a 'Westphal balance on samples of one oil at various temperatures. The relationship (shown in figure28) is a linear one between 20 and 65"C. (68 and 149°F.). It may safely be extended to 100"C. (212°F.). From this graph the speoific gravity of other samples of pilchard oil at various temperatures may be found provided that the value at one temperature is known. This value is plotted as at A in the graph and a line drawn through the point parallel to the original curve. (This is shown by the dotted line in the figure.) The specific gravities of the new oil may then be found for any temperature between the limits shown.

128 From the above data it was calculated that pilchard oil has a coefficient of cubical expansion of 0.00075 ccs. per cc. per degree C. (0.000415 cu. feet per cubic foot per degree F.). This checks very closely with large :ocale experiments and may be used with reasonable accuracy for industrial computations. The deposition of stearine from pilchard oil has been dealt with on page 72. Those properties of pilchard oil which depend upon its chemical composition will now be briefly considered. They are all more or less dependent upon the unsaturation of the oil and include the drying properties and such processes as polymerization, oxidation, hydrogenation and related reactions.

� 92 'OC� i"'.. � "- 91 75 � � 91 50 � 9125

�>.. 91OQ r-- " �� " tD 7590 u " .00'50 I� 4':. � OJ " .'Xlk?5 '""'�

VjCl.. 90DC c--- , I � 8975 � �

89)5C � 89'25

8900 25C 30 C 35t::I 40 C 45 C 50 C 5YC 60"(:: 65�C. 77"F e!i" F 95"F I04'PI 113'F 122'F 13 1' F 140'F 149'F TemperaTu re 28. Spec,f:cgra vity of pilchard oil at various temperatures. FIGt'RE

DRYING PROPERTIES Pilchard oil is not yet widely known as a drying oil because of its com­ paratively recent appearance on the market. To facilitate its use in the protective-coating industries, therefore, a detailed study of its properties and film qualities has been made in these laboratories. Results already obtained have shown that Canadian pilchard oil is one of the best of drying fish oils. I t dries more rapidly than linseed and gives tough rubbery filmsuseful for many protective-coating purposes. Pilchard oil, therefore, is of value wherever drying fish oils are required in the manufacture of paints, waterproofs, linoleum, printing inks, etc., as well as for oil-tanning chamois and other soft leathers, Pilchard oil used in protective coatings should be refrigerated or "wintered" and preferably refined. Thus treated it is a pale-coloured oil with an iodine value between 186 and 190.

129 !J POLYMERIZATION Because of its highly unsaturated nature, pilchard oil may readily be poly­ merized by any of the methods described in Section V. Only a few of the specific details will be mentioned here.

BODYING BY HEAT The. following graphs (figure 29) show the changes that occur in iodine value (unsaturation) , refractive index, free acidity and viscosity, when pilchard oil is heated at 150, 175, 200, 250 and 300°C. respectively (300, 347, 392, 482 and 572°F.) in an inert atmosphere* for periods up to 24 hours. It is evident that · the reaction speeds up greatly after 200°C. (392°F.) reaching a critical tempera­ ture at about 275°C. (527°F.). Above this temperature, decomposition is very extensive as indicated by the acid value. At 300°C. (572°F.), the oil becomes dark and polymerizes to the extent that when cool it sets to a rubbery gel. Bodying in vacuo gives a paler and superior product because of the more complete removal of low-boiling components.

BLOWING Pilchard oil readily oxidizes and polymerizes when blown with air at higher temperatures. The process is accompanied by extensive decomposition and darkening of colour, especially above 200°C. (392°F.). If continued, the oil polymerizes to an extremely viscous rubbery mass of great tensile strength, elasticity and extensibility. When pilchard oil is mixed with linseed oil and blown until gelled, the resulting rubbery mass is an extremely viscous fluid, as contrasted with the granular product of linseed oil alone. The mixed product is valuable as a binder in linoleum because of its homogeneous nature and flexibility.

POLYMERIZATION BY SULPHUR AND SULPHUR CHLORIDE Pilchard oil reacts with sulphur at higher temperatures as do other highly unsaturated oils, giving a dark-coloured spongy-rubber-like product useful in the preparation of cutting oils. Sulphur chloride reacts with the oil to give a dull, tough rubbery gel. The reaction takes place much more slowly when the oil is firstdisso lved in a solvent such as chloroform. Under this condition the product is transparent. Rubbery substances produced by this method are commonly known' in industry as "factices" and are useful as rubber substitutes in the manufacture of various products.

STEAM DISTILLATION AT HIGHER TEMPERATURES The polymerized residue from this treatment is a very sticky, transparent rubbery substance of great extensibility and tensile strength. On exposure to air it dries on the surface and becomes non-tacky. The substance is not readily soluble in common solvents but, like rubber, absorbs the solvent and swells. *A continuous current of pure nitrogen was used to expel volatile products of decomposition during the experiments and the oil was stirred by means of a mercury-sealed stirring device. 130 190.0 '... 1. 10«> , 17$ ""- 1.41/0 0 r--.

1·4820 r---- r---.., r- "-  t-- .l.!!!l - \\ 17D. o i- \ t:-

0 i"- 160. \ , ...... -!------1\ r--� 140. 0 t::: \ • : �1.4IN � ..s · '\ lao.0 \ 1.49' � � M'ZO 1""- I'" � � � IZD. 0 � 1.4" · I'-- c! 'I'-- "'f�

,on Time Houri Ti me in Houra

10.00

'4.00 :;oo'c �

'To DD / 16.0 0 V

l7. I"" 15.0 · L '.85 ''1. 00

1.130 � 'S.D0 I{ II 1\ '2.00 \ 11.0 · IJ/ = .. 10.C 0 �\ j II m 1\ � aD 0 :!. V"� l\. « S.o 0 II "\.: -- "'$"(: J. 1.25 ,...... " �o -..... ---:-- 1.20 \ - - 5,.• I "- :- us oJ Uo � 3.0 o f 1.05 ""- 2 •• 0 !IIO "'" I•• · I. .. " ,. 20 .. H • • • I. I I I. I .. .. ;n Hour. ;n 7lme Time HDur5

FIGURE 29. Changes taking place in pilchard oil when heated in vacuo.

131 On prolonged contact it gradually depolymerizes, and goes into colloidal solution. Solvents such as benzene, toluene, xylene, bring about the disintegration more readily than others such as chloroform, carbon tetrachloride and ester solvents. Furthermore, they give brownish solutions as co�pared with the pale coloured solution of the latter group of solvents.

DRIERS The comments previously made regarding driers in Section V, are applicable also to pilchard oil. Thus the amount and kind of drier required depend on the type of pigment used and also on the nature of the product. Using pilchard oil with white lead and zinc in experimental paints, the writers have found that cobalt drier (I'iholate) used alone, gives films that combine the maximum of hardness and extensibility. Amounts in the neighbourhood of 0.05 per cent. (calculated as cobalt oxide on the basis of oil used) give good drying but 0.10 per cent. gives considerably harder films. Larger amounts give rise to surface drying and necessitate the use of small amounts of cerium or lead driers. Manganese driers while good accelerators do not dry pilchard oil films as hard and glossy as do cobalt driers. Furthermore they possess the defects previously enumerated. The best proportion of manganese drier, however, is about 0.2 per cent. (as oxide) . Resinate driers of cobalt, manganese, etc., while contributing somewhat to hardness of films tend to make them brittle and less flexible. In addition, resin soaps are inclined to precipitate out. In waterproof materials also, where flexibility is desired, cobalt driers are preferable. Yellowing* is a defect common to the majority of drying oils. It is especially pronounced in white paints containing lead pigments, when used for interior work not exposed to direct light. It is, however, shown also by oil films alone, when aged in diffused light or in the dark, and is especially marked in white paints made from a mixture of pilchard oil and Chinawood oil. The defect in pilchar.d oil paints has been eliminated (1) by using polymerized oil, and (2) by using sulphur-dioxide-treated oil.

PILCHARD OIL PAINTS Pilchard oil is of great value in the manufacture of heat-resistant paints, and in paints for metal surfaces and fabrics, subject to expansion, contraction and folding. It is also valuable when used with linseed oil in exterior paints for woodwork under climatic conditions that ordinarily cause linseed oil paints to crack and chalk. Paints made from pilchard oil treated in various ways and also from mixtures with linseed oil or China wood oil, are being tested at the present time. Those of pilchard oil are of very good appearance and in many cases are difficult to distinguish from others by simple observation. The effect of the various trcat-

*This should not be confused with the yellowing tint imparted to white paints by the colour of the oil itself. Such yellowing is counteracted by the addition of very small amounts of ultra­ marine blue. 132 ments on the durability of films, however, will not be known until the weathering tests are complete. Pilchard oil is valuable also for other protective-coating purposes such as in the manufacture of linoleum and water-proof oiled fabrics. Its drying prop­ erties furthermore make it useful in printers' inks and the tanning of leather. Their application is similar to that described in a previous section. Hardness in films often has a marked influence on other properties such as gloss, impermeability to moisture, freedom from tackiness, etc. Usually, therefore, an improvement in hardness also results in improvement of the others. At the same time, increasing the hardness often results in reducing the flexibility and extensibility of films by making them more brittle and of less tensile strength. All these, therefore have to be considered in processing the oil. Among the chief means of producing harder films are : 1. The use of hardening driers and certain pigments. 2. The admixture of boiled linseed oil or China wood oil. 3. The incorporation of gums and resins. 4. Drying at higher temperatures. This of course can be done conveniently only in special cases. 5. Treatment of the oil with sulphur dioxide. The writers have found the last treatment of much value for hardening pilchard oil films. It consists in bubbling sulphur dioxide through the oil until the latter is physically saturated. As the treatment proceeds, the oil becomes darker, especially if slightly oxidized to start with, and also in the presence of moisture and light. The dark colour is presumably due to an extremely finely divided dispersion of carbon particles through the oil as a result of the charring action of sulphuric acid formed from the l;lulphurdio xide and water in the presence of light or peroxides. The excess sulphur dioxide may then be removed by wash­ ing or by heating in vacuo. Washing usually removes much of the dark colouring matter, but the removal may be made more complete by using filtering earths. A considerable excess of sulphur dioxide in the oil is easily taken up by white lead and other pigments used in paint. Pilchard oil thus treated tends to form films more quickly. Furthermore, its "wetting power" is increased and the resultant films are harder, tougher and freer from tack while at the same time their extensibility is slightly less.

HYDROGENATION In a previous section it has been shown how a liquid unsaturated oil can be hardened by the chemical addition of hydrogen. Pilchard oil is no exception. I t can be hardened to a snow-white solid fat having no odour or taste. As pointed out in another communication (Charnley 1931) successful hydrogenation depends to a great extent upon the conditions under which the process is carried out. It has been found that the rate at which hydrogenation proceeds and the com­ position of the products are affected by such factors as temperature, pressure, quantity and kind of catalyst, presence of catalyst poisons and the efficiency of mixing. These factors vary in their effect dependent upon the composition of 133 the oil. 'When a commercially "new" oil is to be hydrogenated on a large scale it is of obvious importance that these factors be investigated. Rate oj reaction. Pilchard oil can be hydrogenated readily with a sup­ ported nickel catalyst (Charnley, loc. cit.). The velocity of the reaction is very rapid for the first tenth of the hydrogenation period and is almost constant. (See figure 30.) Between the first and second tenth of the total hydrogenation interval there is a sudden change in the rate, dropping down to about one fourth of its original value. From the end of the second tenth the rate decreases almost uniformly until the hydrogenation is complete. The rate of mixing of the oil and hydrogen has a great effect on the rate of hydrogenation. For example, keeping the size of apparatus and the speed of agitation constant, an increase in the amount of oil (containing 1 per cent. nickel catalyst) from 2.5 cc. to 15 cc., changed the time necessary for complete hydrogenation from 50 minutes to 300 minutes. In the design of large-scale hydrogenating equipment, thorough mixing is usually provided for.

40

�-t!c " 1""\ .:.:: t:

e-�c .30 w.. ..a Q.. " i:? tW .,!!. w 20 �e:o ., {;� :20 /0 <-o� .� --- .:2d - � .; ---- 5 /0 /5 20 25 30 35 -10 45

in 7ime l1inufcs FIGURE 30. Changes in rate of hydrogenation of pilchard oil under constant condition.

Catalytic poisons. Preliminary work on the effect of non-fatty substances occurring naturally in oils indicates that these may considerably retard the rate of hydrogenation. In a series of experiments, small quantities of impurities which might possibly be found in low-grade fish oils, were added to samples of a refined pilchard oil. These mixtures were then hydrogenated with results shown in table XXII. Relation between analytical constants. In commercial hydrogenation it is important to follow the course of the process very closely. Since this has to be done very rapidly, it is customary to determine the refractive index or melting point. It is valuable, in practice, to be able to calculate the degree of unsaturation or the amount of hydrogen absorbed. This can be done from the easily-determ­ ined refractive index. The relationships that exist between the various analytical constants have been determined for pilchard oil. In the graph below is given the relationship between the iodine value and the refractive index. 134 TABLE XXI I.-Influence of small amounts of impurities on rate of hydrogenation of pilchard oil

I Effect on rate of Substance added Active constituent � Concentration hydrogenation �

� � � i Organic sulphur . Cystine - I 0001% Rate decreased to 1/4 -I I original value. Glycine .. I Organic nitrogen . 010% Rate decreased to 1/2 I original value. Lecithin .. Organic phosphorus. 1.0% Rate decreased to 1/20 original value. I Oxidized oil . I Organic peroxides ... 1 .8% Rate def:reasedto 5/6 original value. \Vatersoluble nitrogenous mat- ter from decaying fish flesh.. Amines . . .02% Rate decreased to 1/3 original value. -�-�------�

200

160 ./"" �

� 120 v----- • � -= � • 80 � V � � � / 10 / / /'" /.1170 1.4490 /. 45/0 14530 1.1550 14570 11590 1.46/0 11630 !.4650 14670 Indices Refracflve FIGURE Relation between iodine value and refractive index of pilchard oil. 31.

By controlling the degree of hydrogenation it is possible to produce fats of different melting points. The characteristic odour of fish oil disappears after a very slight amount of hydrogenation, in fact before any solid fat has been formed. For edible use as shortenings or for use in soaps these hydrogenated pi-oducts are valuable raw materials. It is evident that pilchard oil may be converted into many useful commodities by this process.

COMMERCIAL SALMON OIL

Commercial salmon oil is recovered from the waste from salmon canneries and salteries. The amount of this oil produced in British Columbia in 1930 was about 60,000 gallons. During the same year there were produced 2,221,819 cases of canned salmon. From data obtained over many years it is estimated that it requires 84 lbs. of fresh fish to produce one case (48 Ibs.) of the canned product. For every case produced, therefore, there is a waste of 36 pounds, made up of heads, tails, intestines and gurry from the "iron chink". A rough estimate of the amount of oil lost in this offal is shown in table XXIII.

TABLE XXII I.-Estimated amount of oil in British Columbia salmon cannery waste «1930)*

Cases of Average Calculated Calc. yield in Amount of Kind of fish canned oil weight in gals. oil per oil in product contentt tons of offal ton offal gallons

Sockeye ...... 519,711 8 .6% 9,354 25 (actual 283,850 Springs ...... ' .. 36,517 13 .4% 597 43 practice) 25,671 Cohoes ...... 150,168 8.5% 2,703 25 67,252 Pinks ...... 1,111,937 6.2% 20,014 18 360,252 401,900 Chums ...... 5.1% 7,234 14 101,276 Steel heads .... 1,577 20 .0% 28 58 1,624

The yield of oil per ton of offal was calculated from the average oil content of the canned product taking the actual average yield of a plant operating on sockeye (25 gals. per ton of offal) as a basis. The difference between the amount of oil available for recovery and that actually recovered is very large. However, the economical and technical difficultiesattendant upon the successful production of oil and meal from cannery offal has already been dealt with. It is sufficient to emphasize the fact, that with the slowly but steadily growing demand for fish by-products, particularly for animal feeding, salmon offal will some day be made to yield profitable returns. Commercial salmon oil ranges in colour from a light orange yellow to a deep red. The acid value is usually higher than that of oils produced from fresh herring or pilchards. The reason for this is that the material is not always processed in the strictly fresh condition. A large part of the offal consists of the salmon viscera which are very rich in enzymes. Consequently such raw material decomposes much faster than fresh whole fish. Some fish meal and oil factories collect the offal from canneries in a large area and it is not possible, by this arrangement, to process the material while absolutely fresh. An analysis of a commercial salmon oil is given in table XXIV.

TABLE XXIV.-Analyses of commercial salmon oil Specific gravity at 25OC. . . . 0.9161 Refractive index at 25°C . . . 1 .4790 Colour in Lovibond units . . 29 .9 V, 9.0 R Acid value ...... 11 .16 Saponification value . . . . 193 .2 Iodine value ...... 147.6 Ethef'i nsol. bromo glycerides ...... 36 .4 Vitamin A (by SbC1a, Lovibond blue units, 10%) . . . . . 2.7

*The exact amount of salmon oil produced annually can only be estimated. In fisheries statistics it is included among a number of miscellaneous oils. tFrom Shostrom, Clough Clarke-A chemical study of canned salmon, & J. Ind. Eng. Chem., 283, 1924. 16, 136 These values may vary over a wide range depending upon the nature of the raw material, since oils from the various species and from the same species caught in different localities, vary somewhat. Bailey and Johnson (1918) examined numerous samples of oils from canned salmon and found that each species varied over a fairly definite range. Table XXV is taken from their data.

TABLE XXV.-Range of unsaturation of various salmon oils*

Iodine Insoluble Kind of salmon numbers bromides

Common name Scientificname Lowest Highest Lowest Highest

Red, sockeye, or blueback .. Oncorhynchus nerka ...... 140 .'72 148.19 32 .61 37.35 Chinook, king, or spring .... Oncorhynchus tschawytscha 126 .62 134 .48 23 .86 31 .06 Medium red, coho, or silver- side ...... Oncorhynchus kisutch ..... 152 .51 166.40 43 .07 59 .31 Humpback or pink ...... Oncorhynchus gorbuscha . . 153 .58 40 .17 Chum or dog ...... Oncorhynchus keta ...... 133.10 147 .75 27 .59 35 .33

The present writers have found from the examination of a large number of fish that considerable variation exists in the properties of the oil from fishof the same species. In the following table is given the analysis of the oil from 10 redspring salmon. These fishwere absolutely fresh, the oil being separated from the flesh at sea, within half an hour of the time the fishwere caught. It has been found in these laboratories that the nature of the oil from the dark muscle of salmon is different in character from that of the pink muscle. This difference is shown above where the letter P refers to oil from the pink muscle and D to that from the dark muscle. Usually the oil from the pink muscle is of a lower degree of unsaturation than the dark. It has also been found that the iodine value of the oil taken from the flesh near the head is higher than that of the oil from the tail. In one specimen the iodine value of the oil near the head was 110 and that near the adipose fin 105. The red and a part of the yellow pigment of salmon oil can be removed by treating with bleaching earths or by alkali refining. In the former case, the pigment is apparently destroyed but in the latter it is merely adsorbed by the settling soap and can be recovered. In a typical decolorizing experiment 400 grams of commercial salmon oil were heated on a water bath to 98°C. (208°F.) and then intimately mixed during five minutes with 30 grams of an activated British Columbia bentonite. The mixture was immediately filtered through a suction filter. The results obtained were as follows : Lovibond Units Yellow Red Before treatment...... 29 .9 9.0

A ter treatment ...... 7.0 0.5 f . .. *From Bailey, H. S. and J. M. Johnson, 999 (1918) . J. Ind. Eng. Chem. 10, 137

10 TABLE XXVI.�-Variation in character of oil from fresh red spring salmon

! Sample Acid Iodine Saponification Refractive I no. value value value index

1P 002% 100.8 196.1 1 4691 1D " 112.8 196.1 1 .4705 2P " 98 .5 .4688 196.8 1 2D " 110 0 194.4 1.4703 3P " 119.3 192.6 1 .4716 3D " 1l8 .4 195 .5 1.4723 4P " 124.1 194.4 1.4719 4D " 132.5 196 .0 1.4729 5P " no oil no oil 1.4691 5D " 104.5 no oil 1.4696 9P " 104.5 no oil 1 .4701 9D " 113.8 194.8 1 . 4708 12P " 105 .5 no oil 1.4700 " - 12D 1l8.3 193.8 1 .4713 111" " 133.3 192.9 .4693 1 lID " 124.2 193 .4 1 .4707 13P " 127.1 191 .1 1.4720 13D 123.7 191 .1 4719 1. 16P 91 .8 no oil 1.4696 16D 11l .4 no oil 1.4690

TABLE XXVII.�--Changes in salmon oil when blown with air at 100°e . (212°F.)

Mol. wt. Ether insol. Viscosity Time of blowing Iodine value (Rasts') bromo 1 cc. pipette (\vijs, ! hr.) method glycerides at 100°e. "-_., --�.-�--- I!,- .------�--.- i ' --�------�- hours ---I seconds 0 108.4 229 21 .5 2 102.9 238 14 .3 17 .0 . 4 94 .7 247 7.1 17 .9 6 88 .3 281 5.1 21 . 8 8 82 .3 295 3.3 25 .9 10 77 .3 361 2.0 29 .8 12 70 . 1 427 1.0 32 6 14 67 . 4 434 0.2 38 .2 16 65 .6 524 0.13 48 .3 18 62 .3 606 0.19 49 .3 20 58 .4 687 Trace 51 . 7 22 57 . 4 Trace 5:3 . 7 24 52 .4 Trace 61 .3 26 50 . 2 0 ;32 43 .4 0 Very viscous

138 The red pigment is more unstable than the yellow. When a red salmon oil is heated to 140°C. (284°F.) the red pigment disappears rapidly. In the presence of oxygen it is very unstable even at low temperatures. This pigment may be destroyed by conditions which do not al�er the other characteristics of the oil. In one experiment a deep red salmon oil was heated rapiQly to 140°C. (284°F.). In 2 minutes the red colour had disappeared but there was no change in the iodine value of the oil. Salmon oil, however, is easily oxidized. The analytical data ip the table below indicate the changes that take place when red spring salmon oil is blown with air at 100° (212°F.) for 32 hours. As will be seen, the degree of un saturation steadily decreases while the viscosity and molecular weight increase. The final product was very viscous but did not .gel. It had an oxidized fatty acid content of 13.8 per cent. The behaviour of salmon oil when exposed to the air in thin filmsis shown in the following table. Raw salmon oil does not form a non-tacky film ; samples exposed for several months became thick and viscous but were always of a fluid nature. The addition of linseed oil improved the film in a degree proportional

TABLE XXVII I.-Rate of drying of salmon oil films as compared with linseed oil

Sample Setting time Drying time

__ I (1) "Boiled" linseed oil ..... 7 hours hours J 21 (2) "Boiled" linseed oil ...... 7 hours 21 hours +2% manganese resin ate 3) Raw salmon oil ...... ( N at dry after 3 months .

(4) Raw salmon oil ...... 8 hours Never uite dry. Always q +2% manganese resinate . tacky . ) 25. (5 Raw salmon 75%, linseed oil % .. 8 hours Better than no. 4. +2% manganese resin ate (6) Raw salmon 50%, linseed oil 50% .. 8 hours Dry III 24 hours, but still +2% manganese resinate . . . tacky. I to the amount added. The addition of a cobalt salt as a drier accelerated the drying process but the resulting film was still tacky. Paints made from salmon oil in these laboratories exhibited the tacky properties of the films even after several months' exposure. Gardner ( 1920) has examined salmon oil for its possible use in paints and claims that with 10 per cent. drier it sets to a fairly firm film in three days. Gardner also mentions the experience of a chemist who experimented with salmon oil paints. It is claimed that with suitable driers, a paint made with salmon oil will dry in 18 hours to a good surface. Baked on iron plates, salmon oil forms a good film, which is tough, flexible and durable. Salmon oil, when hydrogenated, forms a white odourless fat. Partial hydrogenation will completely remove the odour of salmon oil but the resulting oil will not dry to a film. Many other methods have been patented for deodoriz-

139 ing salmon and other fish oils but, unless the unsaturated character of the oil is changed, deodorization is not permanent. Bodying by blowing and heat treat­ ment removes the odour but on subsequent oxidation of the oil, it returns. Of considerable importance to the fish oil industry is the fact that salmon oils are potent sources of vitamin D and at the same time contain appreciable amounts of vitamin A. For a fuller discussion of this phase of the subject, the reader is referred to the section dealing with the medicinal properties of fish oils.

HERRING OIL . In 1930, 60,373 gallons of herring oil were produced in British Columbia . This oil was expressed from fresh fish. The Fisheries Department has permitted the use of herring for meal and oil production in northern British Columbia, and to a limited extent in some southern districts. Future regulations affecting the use of fresh herring for this purpose will dependto a certain extent upon the results of an investigation now being conducted by Doctor J. L. Hart, of the Pacific Biological Station, Nanaimo, concerning the life history of the herring, and the conditions of the herring fisheries with regard to possible depletion. While the amount of herring oil now being produced is very small in comparison with the total fish oil production of British Columbia, the possibility of future expansion warrants a consideration of some of the more important properties of this oil. The body of the herring contains a large amount of fat. The actual amount varies widely, according to the sexual condition of the fish, Before spawning, herring may contain as high as 30 per cent. fat while after spawning, it may be as low as 5 per cent. The liver of the herring is very small but contains an appre­ ciable amount of oil. It is probable that the vitamin potency of commercial herring oils produced from whole fishis due to the admixture of oil from the liver. Samples of herring oil examined in these laboratories have usually been of a light brown colour and have deposited considerable amounts of stearine at ordinary temperatures. The iodine value of herring oil is somewhat lower than that of the oil from the related fish, the pilchard. In table XXIX a few analytical values of British Columbia herring oil are given.

TABLE XXIX.-Analytical data of British Columbia herring oil Specificgravity 25°C ...... 0.9135 Refractive index at 25°C ...... 1 . 4730 Colour in Lovibond units ...... 23 .4Y 1.0 R Volume of stearine at 25°C .. " ...... approx. 15% Acid value ...... 1 .22

Iodine value ...... 118.

Saponification value ...... 187.3 Vitamin A (SbCIs, Lovibond blue units) (10% solution) ...... 1.3

Unsaponifiable matter ...... 1.93

On account of the somewhat lower unsaturation and higher content of stearine, herring oil does not absorb oxygen as rapidly or give such a satisfactory film, as menhaden and pilchard oils. It can be polymerized, however. M. 140 Hirose (1929) gives the following data on the polymerization of a Japanese herring oil, the composition of which is similar to that of British Columbia herring oil. TABLE XXX.-Polymerization of herring oil

Duration Viscosity Saponi- S ample Temp. of d'o 50° 2CJ Acid fication Iodine n DC. heating (Ostwald) D value value value ------�-- Orig. oil ..... 0.9166 43 .8 1. 4745 11.6 188.0 117.1 Polym . Oil . 138 1 " 40 9255 76 .1 1.4774 10.9 187.1 91 . 7 o 2 " 90 0.9303 97 .2 1.4 777 10 .1 187.2 84 .8 3 " 120 0.9315 109 .0 1.4782 10 0 187.5 82 .4 4 " 180 0.9363 135 .3 1.4 792 10 6 187.0 77 .9 5 148 190 9369 135 .9 1 . 4794 6.0 186.7 75 .3 o�. 6 " 240 0.9371 146.5 1.4 793 5.5 185.8 74 .6 i , -��--- i .-

Below 250°C. (482°F.) polymerization did not take place. Above this tempera­ ture, the reaction proceeded fairly rapidly. The characteristic fishy odour dis­ apI=eared and the oil gradually thickened. In order to eliminate oxidation and consequent darkening, polymerization was carried out in an atmosphere of carbon dioxide. After polymerization, the relative efficiency of the sodium soaps of various samples was compared by means of the drop number"'. M. Hirose gives the data on this part of the work (Table XXXI).

TABLE XXX I.-Drop number of sodium soaps of polymerized herring oil

------Iodine Drop number at Sample value --_.-- of oils C 60DC. 80°C, ______------_._------i __ 1 �� �_ I I Dist. H2O .. I 14 14 5 15 I Oci'. ou. . 117 1 70 I 76 16 ! Polym. �amples: I l 91 . 7 56 61 69 . 2 84 .8 55 .5 59 .5 67 I 3 82 .4 62 64 68 .3 I 4 77 .9 63 .5 64 . . 69 .5 I 5 1I 75 3 58 5 61 . 5 63 I .5 6 74 .6 51 57 . . 61 .5 5 I ---_. I I t is interesting to note that the drop number passes through a maximum at an iodine value of about 80. The drop number at this maximum is not as high as that of the soap of the original unpolymerized oil but the soap from the former is free from odour. A characteristic odour is very noticeable in soaps made from

*The "drop-number" is determined by counting the number of drops formed when a definite amount of liquid is allowed to run slowly through a fine orifice. The greater the number of the drops the better the lathering property of the liquid. 141 the raw oil. This observation may be of interest to soap makers who may wish to use herring oil in laundry soaps, since polymerization is a much cheaper way to effect deodorization than hydrogenation. Another method for the deodorization of herring oil has been tried by M. Hirose and Shomonura (1929) and also in these laboratories. This consists in passing chlorine through the oil until the fishy odour has disappeared. Un­ fortunately, free chlorine and hydrogen chloride are constantly liberated from the oil even at ordinary temperatures and therefore from a practical standpoint, this method is not of value. The hydrogenation of herring oil has been studied by a number of invest­ igators. Ueno, Yamashita and Ota (1929) hydrogenated herring oil at a tempera­ ture of llO-1l5°C. (230-239°F.) with a nickel catalyst. Table XXXII is taken from their data.

TABLE XXXIL-Properties of raw and hydrogenated pilchard oil Melting Reichert-! I5°(100) 20° point Acid ' Sapon. Iodine Meissel. I d n , 4° (4) (400) I value value value value 1 D dc. I -- --- I --- I ---- I ------1 - - Unhardened ... . . 0.9174 4712 0 24 187 1 10 6 0 7 I 5 1 4588 31.1-34.7 I Hardened ...... \ 0.8555 [ Ii 0 25 187 0 1, 55 7 0 4 I t will be noticed that although the iodine value was lowered only to 55.7 the melting point of the resultant fat increased to 34.7°C. (94°F.). The total amount of hydrogeriation required was not very great since the original oil was not highly unsaturated. Consequently, herring oil constitutes a good raw material for hydrogenation. From a series of experiments designed to determine the nutritive value of the hardened and raw fish oils the above authors concluded that the hardened products were equal, if not superior to natural fats. In a more recent communication (L931,)the same authors report the effectof ultra-violet treatment of the hardened fat. Table XXXIII gives their analytical data.

TABLE XXXIIL-Effect of irradiation on hardened herring oil

Sp. Gr. Ref. Index Acid Sap. LV. I Oils (d,o) (nn) lVL P (0C.) value value (Hanus) ------Herring oil I Original oil ...... 0.9253 (15°) 1.4768 (20°) 1.79 187.1 144 9 Hardened oil ...... 0.8573 (100°) 1.4583 (40°) 39 . 8-41 .3 0.71 186.3 60 .5 Hardened oil, irra- diated ...... 0.8580 (100°) 1.4589 (40°) 39.5-41 . 2 0.97 186.7 59 .7

The various samples were tested biologically for nutntlve value and the irradiated hardened samples were found to possess increased antirachitic prop­ erties. The physical and chemical properties of the fat were not changed by

142 irradiation. The vitamin content of the raw oil has already been referred to in the section on the utilization of fish oils. If herring oil is produced from fresh whole fish in a modern plant it is a suitable product for animal feeding.

GREYFISH LIVER-OIL

The greyfish , or dogfishas it is more commonly called, belongs to a primitive family of small sharks. The species found on this coast is quite similar to the Atlantic greyfish, differing in the shorter spines preceding the dorsal fin. These fish live entirely upon smaller fishes and do considerable damage among the food vaneties. Great havoc is sometimes caused by schools of greyfish on the lines and nets of fishermen. They are regarded as a serious nuisance in almost every fishery of the world and therefore, if greyfish can be made commercially valuable, a dual purpose will be served. The greater part of the oil of the greyfish is stored in the liver. From an examination of 180 fish, it was found that the livers constituted 10 per cent. of the average weight of the fish. The oil content of the livers varies between 45-65 per cent. Very little commercial oil is produced, 14,558 gallons being total production in British Columbia for 1930. This oil is manufactured from the whole fish. Many attempts have been made in the past few years to establish a steady market for the product but with indifferent success. Manufacturers in other countries, particularly in England, are also finding difficulty in disposing of this oil. I t was with the view of findingfurther uses for this oil that the Experimental Station made an investigation of its properties. (A full account of this investiga­ tion will be published later.) This examination has been confined to the oil obtained from the livers of the Pacific coast greyfish. The oil was produced by steaming the livers of freshly caught fishand separating the oil from the pressed, cooked material. The analytical data of the oil are given in table XXXIV.

TABLE XXXIV.-Analytical data for British Columbia greyfish liver oil Specific gravity at 25°C ...... 0.9055-0 .9066

Specific gravity at 40°C...... 0.8947 Refractive index at 25°C...... 1.4714 (aB) Refractive index at 25°C...... 1.4721-1 .4730 (DKa) Optical activity (20 cm. tube at 25°C.) ...... , . ... . - 3.4° Viscosity in poises at 25°C ...... 0.4923 at 40°C...... 0.3248 Saponification value ...... 156-166 Iodine value ...... 112-115 Acid value ...... 0.57 Titre of fatty acids ...... 25 . 22 Acetyl value ...... 5.5 Unsaponifiable matter ...... 4.5-14 5% Colour in Lovibond units ...... 2.7Y, 0.2R Vitamin A (by Sbe1, Lovibond blue units) (10% solution) ...... 23 . 2

143 The oil has a pale yellow colour and when prepared from the strictly fresh livers has a faintly fishy, butnot objectionable odour. It contains little stearine, the freshly-prepared oil remaining fluiddow n to - 5.6°C. (25°F.), when it becomes turbid and gradually turns semi-solid. I t is to be noted that the unsaponifiable matter varies over a considerable range. So far, no explanation has been found for this variation. Oil from fish caught in waters of northern and southern British Columbia have shown varia­ tions over approximately the same range. The unsaponifiable matter of this liver oil .has been examined by E. G. V. Percival (1932) and has been shown to contain 5 per cent. cholesterol, 85 per cent. squalene, and 10 per cent. of higher alcohols. Greyfish-liver oil can be hardened by hydrogenation. \Vhen the process is carried out at 180°C. (356°F.) and at ordinary atmospheric pressures, the odour disappears after fifteen minutes, but up to that time no solid fat forms. The decrease in unsaturation due to hydrogenation is very rapid at the first part of the process but gradually falls off until the saturation point is reached. It is not necessary, however, to saturate the oil completely to obtain a hard fat. In a typical experiment, the raw oil with an iodine value of 117.3 and a melting point of -100C. (14°F.), was reduced by hydrogenation until the iodine value decreased to 50.8. The melting point of the product was then 34.5°C. (94°F.). The fat was almost pure white, quite hard and without odour or taste. The potassium and sodium soaps were white, odourless, hard and firm, and gave a fairly good lather. Furthermore, they did not deteriorate on standing. Liver oils usually contain certain types of unsaponifiable matter that rapidly inactivate the nickel catalyst used in the hydrogenating process. A preliminary refining is therefore nearly always necessary. Alkali refining has been found satisfactory. Ellis (Hydrogenation of Organic Substances, page 49) has described a method of purifying liver oils by using copper hydroxide. This chemical appears to exert a somewhat specific action, for, although the colour of the oil is not improved, a great deal of the catalytic poison is removed. Greyfish-liver oil is not highly unsaturated as are the body oils of herring, salmon and pilchard. Iodine values of samples produced on this coast vary between 110 and 120. Since this oil differs considerably in its properties from the body oils, it is interesting to consider the composition of its fatty acids. From a preliminary investigation into the composition ·of the greyfish-liver oil of the Pacificcoast, it has been found that the solid fatty acid content averages about 15 per cent. of the total fatty acids. The solid mixture consists chiefly of palmitic acid with a small amount of stearic and behenic acids. ?9 per cent. of the total fatty acids consists of those acids with more than two double bonds, while the remainder-55 per cent. , consists chiefly of mono- and di-ethylenic acids of the CI8 and C22 groups. Toyama and Tsuchiya (1927) have analysed the oil from a dogfish indigenous to Japanese waters (Squalus wakiyae). They found the unsaponifi able matter to average 16 per cent. of the total weight of the oil. The saturated fatty acids 144 amounted to 15 per cent. of the total weight of the fatty acids and consisted chiefly of palmitic acid with traces of myristic, stearic, arachidic and behenic acids. The highly unsaturated fatty acids consisted chiefly of the C20 and C22 series with a smaller amount of the CIS series. Acids with only one double bond were chieflyof the CIS series with smaller amount of the C20 series. The results of an analysis of the oil of greyfishin digenous to the waters of Great Britain have been reported by Guha, Hilditch and Lovern (1930). These authors found that the solid fatty acids of this oil had the following composition : myristic 6 per cent. ; palmitic 10 per cent. ; stearic 3 per cent. The unsaturated acids were composed of the following: Unsaturated acids of the C16 series 9% " ""C1 S " 24% " i, ,, C20 " 29% " ""C22 " 12% " ""C2 4 " 6% An important feature of the composition of these liver oils is the relatively small amount of highly unsaturated acids and the larger amount of acids with only one double bond. For this reason these oils cannot be classed as drying oils. It is true that they absorb oxygen but the product is a viscous, sticky oil. Such liver oils cannot be bodied (or polymerized) to any great extent by heat treat­ ment. In a typical experiment, a large sample of this oil was heated at 250°C. (482°F.) in a vacuum for a period of 48 hours. The iodine value decreased from its original value of 108 to 80 but the viscosity only rose from 0.60 to 0.96 poises at 25°C. (77°F.). A greater effect is obtained by blowing heated air through the hot oil. At a temperature of 180°C. (356°F.) the oil darkens very rapidly and becomes quite viscous. This does not, however, increase its drying properties and it will still give a tacky product when exposed in thin films. The viscosity of the oil is further increased if it is blown in the presence of driers such as manganese and cobalt salts or metallic copper. Since high viscosity oils which deposit no stearine are of value in lubricating certain types of machinery, another method of increasing the viscosity of greyfish­ liver oils was attempted. This consisted in hydroxylating the oil. By treating a sample with hydrogen and oxygen mixture at 180°C. (356°F.) in the presence of finely divided metallic nickel, the hydroxyl content of the oil was doubled and the viscosity was also increased. Another method of some interest consists in passing sulphur dioxide through the warm oil until physically saturated. The oil is then allowed to stand for some time until it turns black. It is then subjected to steam distillation which removes the excess of the sulphur dioxide. The product is an amber-coloured oil of slightly increased viscosity. In a typical experiment, oil with an original iodine value of 108 and viscosity of 0.60 poises had an iodine value of 104 and viscosity of 0.98 poises when treated by the first method and iodine value of 106 and viscosity of 0.65 when treated by the sulphur dioxide method.

145 • It is possible to sulphonate greyfish-liver oil but accurate temperature con­ trol must be maintained over the reaction mixture. On the addition of con­ centrated sulphuric acid to the oil (20 parts of acid to 100 parts of oil) , the oil turns a dark red colour and becomes highly viscous. The mixture gives a persistent emulsion with water. On neutralizing with ammonia, a light-yellow coloured mixture is obtained. Although not completely soluble, this product forms stable emulsions with water in all proportions. vVhen dissolved in 95 per cent. alcohol, or 10 per cent. ammonia, it gives slightly opalescent suspensions. In one experiment the addition of 2 cc. of sulphonated oil to 40 cc. of a 1:1 mixture of petroleum oil and water lengthened the period required for separation from one minute to one hour and 15 minutes. Emulsions made of this sul­ phonated oil were found to be stable up to 100°C. (212°F.). In Canadian Patent No. 276,163 December, 1927, a fly exterminator is described, the chief ingredient of which appears to be greyfish-liver oil. The vitamin potency of greyfish-liver oil has been determined but the reader is referred to the section on the medicinal use of fish oils for this phase of the subject.

MISCELLANEOUS FISH AND FISH-LIVER OILS

In the coastal waters of British Columbia there is a number of commercial fishesof lesser economic importance from which body or liver oils may be obtained. Of the list of oils given below only three have been produced in commercial quantities. These are halibut-head oil, halibut-liver oil, and rat-fish liver oil respectively. With the exception of eulachon oil, little information is available concerning the remainder. It is of interest, therefore, to examine a few of the analytical data of these oils (Table XXXV) .

EULACHON OIL The eulachon (Tlzaleichihys pacificus) is closely related to the European smelt but contains more fat. These fish ascend certain streams of British Columbia in enormous numbers in the spring and are caught in considerable quantities by the Indians for whom the fishing rights are reserved by the Government. The oil of the eulachon is of a light yellow colour. It sets to a buttery solid fat when allowed to cool to lO°C. (50°F.). If prepared from fresh fishit has a not unpleasant odour and taste. Eulachon oil is not highly unsaturated and there­ fore a slight amount of hydrogenation suffices to solidify and deodorize it. The amount of unsaponifiable matter in the sample examined was remarkably high for a fishbody oil. It has not yet been ascertained whether this is an average or an abnormal value. The vitamin A content of this sample, as indicated by the colorimetric method, wa's very low. Eulachon oil has been mentioned by many authors as possessing exceptional medicinal properties. These claims have been based on the supposedly beneficial results obtained by the north Pacific coast Indians. These people, especially 146 TABLE XXXV.-Analytical data of some miscellaneous Pritis:, fish oils Colu:nLia Vitamin A Cnsap. Sb 3 C Source of oil or fat % Colour Colour I. Sap. matter Lovibond oil R Val. Val. % blue units Y 10% solution

---�--"'------'- Eulachon flesh . 1.3 0.1 127 .3 164.3 17 .6 1.0 Black cod flesh . 2.0 0.5 99 . 8 195.2 072 1.2 Black cod liver . 25 .0 Ling cod flesh . 0.9 7 . 5 1.4 136.8 173.1 0.2 0 ing cod liver . 16 .0 27 .0 16 .6 119.8 269 1. 26.9/ 1% Ratfish liver . 50 .0 3.0 5 86 .3 145 5 22 2 4.1 o Grey cod liYer .. 48 14.0 2 3 171.5 182.1 1.3 J 40 4/1% Halibut head . 0.6 o 7 129 .8 191 .2 0.6·1 0 Halibut flesh. 0.6 0.7 140.6 190 . 3 0.8 0 Halibut liver . 1O�20 29 9 6.3 139 .0 176.0 7.6 294 (solvent ext.) 29 4 1% Halibut liver. 10�20 8.8 0.5 141 .3 169.5 7.5 163 (pressed) 16 3/1 % Red cod flesh . 29 .9 9.9 151 .6 185 .9 2.4 0 < .5

------'----',-_ .. ------, those living in the Naas river district, consume large quantities of this fat. Mr. VV. E. Collison, Indian Agent at Prince Rupert, has made numerous valuable observations in this connection during the many years he has been associated with Indian work. In his opinion, eulachon oil has no special medicinal properties, but on account of the large quantities used, constitutes an important food.

BLACK COD OIL The black cod, beshow, or coalfish (A naplopoma fimbria) is not a true cod but belongs to the family known as skil-fishes. It is not the same fishas the east coast coal-fish. The so-called black-cod occurs from Monterey in the south to Unalaska in the north. The fish caught in the south are very dry and tasteless. From the straits of Juan de Fuca northward, they commence to fatten and those caught in the northern waters are exceedingly rich in oil. As a rule, fish which have fat-rich flesh have non-oily livers, but the liver of the black cod contains a large amount of oil, one sample yielding as high as 25 per cent. The body oil is of a light yellow colour and it deposits a large amount of stearine at room temperature (about 60 per cent. of its volume at 18°C. (64.4°F.) ). It is not highly unsaturated, the iodine value averaging about 100. The oil con­ tains little unsaponifiable matter and gives only a slight colour with antimony trichloride. It is interesting to note that the liver oil of the black cod is very high in vitamin A being of the same order of potency as halibut liver oil.

147 LING COD LIVER OIL The ling cod of the Pacific coast is not a true cod but belongs to the family known as the greenlings (Hexagrammidae). This fish is also known as the cultus cod, blue cod, and buffalo cod. They are very abundant in the coastal waters from Sitka to Santa Barbara. Ling cod are very large fish, specimens of 30 to 40 pounds frequently being caught. The liver, which constitutes from 1 to 4 per cent. of the weight of the whole fish, contains 5 to 10 per cent. of oil while the flesh contains approximately 1 per cent. The most important feature revealed by the analysis of the liver oil of these fish is the very high value obtained in the colorimetric assay for vitamin A. The colour produced by a 10 per cent. solution of the oil in chloroform (the standard concentration for this test) was so intense as to be impossible of measure­ ment. With a 1 per cent. solution, a high reading of 26.9 Lovibond blue units was obtained. Good grades of cod-liver oil seldom give an intensity greater than 12 Lovibond blue units in a 10 per cent. solution. On a similar basis, therefore, ling cod-liver oil contains 269 units of vitamin A. These results have been con­ firmed (Bailey 1933) by biological methods. During 1929 there were landed in British Columbia 4,848,900 pounds of ling cod, valued at $383,462.00. The livers of these fishwere thrown away. In view of the high vitamin A potency of the liver oil it would appear to be economically feasible to recover it. As a potent source of vitamin A this oil would no doubt be of interest to manufacturing pharmaceutical chemists.

RATFISH-LIVER OIL The ratfish belongs to the group of fishes known as elasmobranchs. These fish have a cartilaginous skeleton which makes them difficult to process for fish meal and oil. The livers are relatively large, averaging approximately 10-15 per cent. of the weight of the whole fish. The oil content of the livers is very high , in some caEes yields of 50-60 per cent. being obtained. Very little oil is found in the flesh of the radish. The liver oil contains hardly any stearine yet in spite of this it is not highly unsaturated. The oil clouds at -3°C. (26.6°F.) and solidifies at -12°C. (1l.4°F.). The high amount of unsaponifiablema tter present in ratfishoil makes the hydrogenated product of little value for food or soap purposes. \Vhen sulphonated, it gives a product similar to that obtained from greyfish-liver oil. Due to the low unsaturation and to the fact that rat-fishli ver oil does not solidify on cooling it constitutes a good lubricant for certain purposes (i.e., slow-running light machinery) . It oxidizes very slowly and does not readily form acidic products. For these reasons it has found limited use as a lubricating and leather­ dressing oil. GREY COD LIVER OIL

The grey cod is common in Pacificcoast waters from Puget Sound to South­ east Alaska. The larger fishare caught on the off-shorebanks , where specimens weighing 40 lbs. have been obtained. Grey cod caught in the vicinity of Hecate

148 straits averaged between 6 and 7 Ibs. while those caught in harbour waters rarely exceed 2 to 3 lbs. The libers of these fish vary considerably in size. They average approximately 5 per cent. of the weight of the fresh fish. The oil content of the livers is high, the average of nine analyses giving a yield of 48 per cent. The general analytical characteristics of grey cod-liver oil resemble closely those of the cod-liver oil from Newfoundland. The oil is more highly pigmented than the Newfoundland oil showing 14 Lovibond yellow units as compared with units for the latter oil. The samples of oil prepared in this laboratorY,gave an 4 intense colour with antimony trichloride, when using a 10 per cent. solution of the oil in chloroform. When a 1 per cent. solution of the oil was used a reading of 4 blue units was obtained corresponding to 40 units for a 10 per cent. solution. In a 10 per cent. solution, high grade medicinal cod-liver oils from Newfoundland gave colour readings of 7 and 12 blue units respectively.

HALIBUT OIL The halibut fisheries constitute one of the larger branches of the fishing industry in British Columbia. In 1929 there were landed 30,392,100 pounds valued at about 3Yz million dollars. These fish, which belong to the family of flatfi Ehes, have a relatively non-oily flesh. The liver, which constitutes less than per cent. of the weight of the fresh fish, has an oil content varying between ten 2 and twenty per cent. The fishare eviscerated at sea but they are not decapitated until landed. The heads constitute a very valuable raw material for fish meal and fish oil production. The oil from the head of the halibut is a pale yellow limpid liquid which deposits very little stearine. It is not very highly unsaturated and consequently does not absorb oxygen very rapidly. The oxidized product does not set to a solid film but remains thick and sticky. The oil is easily deodorized by partial hydrogenation and since it contains a very small amount of unsaponifiable matter, the hydrogenated product makes an excellent raw material for industrial use. Halibut-liver oil is interesting from the standpoint of its high vitamin A content, 1 per cent. solutions giving values as high as 29.4 Lovibond blue units. The liver oil is more highly unsaturated than the head oil and contains a far larger amount of unsaponifiable matter. It is interesting to note the difference in properties between halibut-liver oils extracted by solvents and those extracted by steaming and pressing. Solvent extraction as a rule yields an oil of a darker colour. While the amount of liver oil obtainable from one fish isvery small, the large quantities of this fish landed annually make it possible to produce a fairly large amount of the oil. From actual practise it has been found that the yield of livers is approximately 25 lbs. per 1200 lbs. of fish. The approximate amount of halibut livers obtainable from halibut landed in Canadian Pacificports should be in the neighbourhood of 600,000 lbs. which at 15 per cent. oil content would yield about 10,000 gallons of oil.

149 REFERENCES

BAILEY, H. S. AND JOHNSON, J. M. J. Ind. Eng. Chem. 10, 999. The determina­ tion of the hexabromide and iodine numbers of salmon oil as a means of identifying the species of canned salmon. 1918. BROCKLESBY, H. N. Studies in fishoils . Grey-fish liver oil. Part A. General properties. Unpublished MSS. BAILEY, B. E. The vitamin A content of ling-cod liver oil. Cont. Can. BioI. Fish. (Industrial Series), 7. Also, BioI. Bd. of Canada, Prog. Rept. No. 12, April. 1932. CHARNLEY, The hydrogenation of pilchard oil. Biol. Bd. of Canada Prog. F. Rept. No. 10, 14. 1931. Fisheries Statistics of Canada for Ottawa. 1931. 1929. GARDNER, H. A. Salmon oil in paint. Paint and Varnish Manufacturers Assoc. Scient. Circular No. 92. 1920. GUHA, K. D., HILDiTCH, T. P. AND LOVERN, J. A. The composition of the mixed fatty acids present in the glycerides of cod-liver and certain other fish-liver oils. Biochem. J. 24, No. 2, 266. 1930. HIROSE, M. Untersuchung tiber Seifen von polymerisierten Fischolen. J. Soc. Chem. Ind. (Japan) Sup. Bd. 115. 1929.

HIROSE, M. AND SHlMONURA, T. Chloriertes HeringsOl und seine Seifen. . J. Soc. Chem. Ind. (Japan) Sup. Bd. 71. 1929. PERCIVAL, E. G. V. Studies in fish oils. The unsaponifiable constituents of greyfish-liver oil. Cont. Can. BioI. Fish. (Ind. Series) . in press. SHOSTRUM, O. E., CLOUGH, R. W. AND CLARK, E. A chemical study of D. canned salmon. Ind. Eng. Chem. 16, -283. 1924. TOYAMA, Y. AND TSUCHlYA, T. Ueber die Fettsauren des Haifisch und Rochen- leberole. J. Soc. Chem. Ind. (Japan) Sup. Bd. 92. 1928, TOYAMA, Y. AND TSUCHlYA , T. On the nutritiva value of hardened oils. III. The influenceof ultra-violet irradiation on the nutritive value of hardened oils. J. Soc. Chem. Ind. (Japan) 61. 1930.

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