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Studies on acid analysis Jones, P. M.

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DIVISION OF BUILDING RESEARCH

STUDIES ON ROSIN ACID ANALYSIS

by Peter M. Jones

Report No. 178 or the Division of Building Research

Ottawa July 1959 PREFACE

Studies of test methods for use in the speoifioations of the Canadian Government Speoifioa• tions Board oonstitute a substantial portion of the work of the Paint Laboratory of the Division. An examination of a method may be made prior to adoption, or methods already inoorporated in speoifications may be re-examined as to reliability through round-robin tests, or may be studied for possible improvement. When it was proposed that an ASTM method for deter• mination of rosin oontent of ooating materials be used in a eGSB specification, it was already known as a result of partioipation of the Paint Laboratory in an ASTM round-robin test that the method was not satis• faotory. The author, who is a research offioer with the Building Materials Section, undertook to determine the suitability of certain modifioations to the original procedure. The results of this work are now reported.

Ottawa N.B. Hutcheon July 1959 Assistant Direotor STUDIES ON ROSIN ACID ANALYSIS

by Peter M. Jones

These studies by the D1.vision of Building Researoh were begun as a result of participation in a round robin test ｵｳｩｮｾ the ａｓｔｉｾ method for "Total Rosin Content of Coating Materials • This procedure is that which was proposed in the 1957 preprint of the report of Committee D-l and is reproduced in Appendix A. The unsatisfactory results that were obtained ｰｾＧｯｭｰｴ･､ further work of which this report is a summary. Preliminary investi• gation was carried out on extraction losses which may occur in the ASTM procedure. A study was made of the factors affecting the degree of esterification of fatty acids and rosin aoids. Preliminary work was also performed on the method proposed by Linder and Persson (2). As a result of these studies modific• ations of the proposed method were attempted, and in addition other methods were examined as possibilities in providing a means of determining rosin acids in the presence of fatty acids. The difficulties in the procedure appeared to be in the esterification of the acids and the subsequent extractions and titrations. Consequently the saponification used for the preliminary separation on a real sample was omitted from the studies. Refined abietic acid and commercial linseed oil fatty acid were used to study experimentally the results of the esterification and extraction parts of the ASTM procedure.

Experiments on Extraction £f ｦｴ｢ｾ･ｴｩ｣ ａｯｩｾ Abietio acid was dissolved in 100 ml of methanol and 5 ml of concentrated H2S04 as catalyst was added. The mixture was refluxed for 15 minutes, washed with Na2S0J, solution and extracted with benzene. The Na2so4 solution removed the acid catalyst and the benzene layer was titrated with KOH/methanol solution using blue as indicator. The results are shown in Table I and indicate a large loss of the rosin acid. - 2 -

Table I Recovery of Abietio ａｾｩ､ ｾ After Refluxing for IS Minutes ｾｮｾ Extracting with Na2S04 Solution

Wt Abietio Acid Normality of KOH Titre %Recoverz (gm) (ml) 1.4643 0.206 16.1 68.5 0.9915 0.206 9.1 ｾＮＸ 1.3951 0.206 9.4 .0 0.7430 0.206 ｾＮＳＵ 36.5 1.0405 0.206 .22 37.2

That this loss might be due to losses in the Na2S0" washing was oonsidered since the wash extraot formed an emulsion wEioh oould contain some abietic acid. It was found that additional abietic acid was reooverod by washing the ｎ｡ＲｓＰｾ solution with benzene and adding the benzene extract to the aoietic acid solution and titrating the whole. Table II shows the improved recovery of abietio aoid. However this procedure does not reoover all the emulsified acid, as is shown in Table III. It is found that washing with Na2S04 solution resulted in a loss of approximately 17 per cent of the abietic aoid present. If the Na2S0" washes were furt.her extracted with ether a small portion (3 per ｣･ｮｾＩ of this 10S8 was reoovered. It is also observed that ether used as solvent produces a highor yield of the acid present than does benzene.

Table. II RecoveFL of Abietio Acld_.- After Ref1uxlng for 15 Minutes end

Extracting with ｎ｡Ｒｳｾｾ Solution and Washing Extracts with Benzene wt Abietic Acid Normality of KOH Titre %Recovery (gm) - (ml) 1.3204 0.206 14.7 ＶｾＮＳ 0.9584 0.206 10.15 6 .7 1.4583 0.206 15.6 67.1 0.8158 0.206 8·5 64.9 ＱＮＰＹｾ 0.206 12.7 62.3 1.07 0.206 11.0 63.7 Table III Effect of Various factors Upon the Recovery-£! Abietic Acid Wt Abietio Normality Acid of KOH Titre ｾ Recovery Comments (gm) (ml) - 1.0005 0.1979 16.5 Straight titration using 1.0589 0.1979 17·3 ｾｾＺｾＴｽ ether as solvent. 1.0025 0.1979 16.6 81.36} No esterification. Extraoted 0.9969 0.1979 16.6 81.52 with Na2S04 using ether as solvent.

0.9964 0.1979 14.1 84.6 } No esterification. Extraoted 0.9981 0.1979 14.1 84.4 with Na2S0J, using ether as solvent ana washing extraot with ether.

1.0002 0.1979 12.1 72·3 } No esterification. Extraoted 0.9829 0.1979 11.85 7200 with Na2S0J, with benzene as solvent ana washed extraot with benzene.

Conclusions from Extraction Studies Washing with Na2S0J. leads to errors due to extraction losses and it would be better to avoid this step. The function of this washing is to remove the acid catalyst prior to titrations of the rosin acids. It would be preferable to titrate the aoid catalyst in the presence of the abietio acid in one of the following ways: i) Titrating potentiometrically the mixture to end points of a pH of 4.0 for the catalyst and a pH of 10.5 for t he rosin acid (Fig. 1); ii) Titrating with thymol blue as an indicator, the end point for the catalyst being shown by the ohange of red to yellow at a pH of 2.8 and the end point of the rosin acid taken at the change from yellow to blue at a pH of 9.6. Both have been used with equal satisfaction. In the work on esterification the potentiometrio titration was used. - 4-

Esterification Studies The effects of the catalyst, time of esterification and weight of sample, have been studied and are shown graphically in Figs. 2,3 and 4, and are summarized in Tables IV and V. The effects beyond an esterification time of 60 minutes and an acid catalyst content of 10 per cent were not studied. From the results it is seen that about 20 per cent of the abietic acid is esterified When 98 per cent of the fatty acids is esterified. These quantities vary considerably with different conoentrations of aoid and time of reaotion. Error,S are produced because of the partial esterification of rosin and the incomplete esterification of fatty acids. Since the amount of fatty acid will greatly exceed the amount of rosin present, the unesterified fatty acid may actually exceed the rosin content. In an analysis of a 40-gm sample of solids containing 0.4 gm (1 per cent) of abietic acid and the remainder fatty aoids using 6Q-minute esterification and 10 per cent acid catalyst. 0.32 gm of abietic acid will remain after esterification, for titration and 0.792 gm of fatty acid. And thus the titration will include a far larger quantity of fatty acid than of abietic aoid.

Linder's and Persson's Method This method (2) uses an azeotropic distillation of the water to promote esterifioation. The esterification solution was prepared by mixing 500 ml of n-butyl , 500 ml of benzene and 6 gm of concentrated sUlphuric acid. The mixture was placed in a flask and distilled azeotropically for 30 minutes. Fifty millilitres of this solution were used with about 1 gm of abietic acid and distilled azeotropically for 20 minutes, cooled and titrated with alcoholic KOH. A blank titration was also made on the same volume of the esterifioation mixture after re• fluxing it in the same manner. The results of this method .... shown in Table VI. - 5 -

Table IV.. Effeot of, Aoid Catalyst and Reaction Time on the Esterification of Abietic Acid and Fatty Acids, Examined SeparatelX

Linseed Oil Fatty Acids Abietic Acids %Aoid Wt %Esteri- Wt %Ester1- Catalyst T1me Sample fied Sample fied (min) (gm) ｾｧｭＩ 0.5 10 1.70 17.5 1.49 9.i4 20 1.J42 24• 4 1.49 9. 1.52 37.6 1.49 13·5 ｾｧ 1.92 50.9 1.49 13.5 1.0 10 1.63 ｾＮＹ 1.50 7.6 20 1.61 .4 1. 10.9 1.56 52.7 1. 5 13·3 19 1.51 77.2 1.5647 12·3 5 bra 1.67 98.6 1.53 19·3 1.5 10 1.52 37.2 ＱＮｾＹ 7·2 20 65•4 1. 2 IS. 30 lr1•.9 9·2 1.53 15.6 50 1. 8 85. 1.60 15.9 2.0 10 1.48 60·2 1.46 11.2 20 7 . ＱＮｾＲＵ 13.6 ｩＺｾＲ 8 .3 1. 01 11·3 6g 1.62 95.74 1.96 15.1 3.0 10 1.525 11.4 20 1.55 2 1.65 94.1-- 1.57 ia·.9 6g 1.52 95.8 1.53 17.1 5.0 10 1.g2 12.6 20 1.50 92.5 1. 2 ｊＱｾＮＸ 1.57 96.9 1.50 6g 1.51 96.0 1.51 11l·0 .2 7.0 10 - - 1.5 ｾＮＱ 20 - - 1.56 1 Ｎｾ -- -- 1.° 16. 6g .- - -.- 1.56 17.4 10 10 . . 1.58 20 1.53- 97.9- 1.51 17·t19. 1.57 98.2 21.7 6g 1.53 98.1 1.1·ft38 22.1 - 6 -

Table V

Effect of SamEle Weight onftsterification of Abietic Acid and Fatty Aoids, Examined SeEarately by using ＱＰｾ Acid Catalyst and 20 Minute Period

ｾ Esterification ｾ Esterifioation -...... of Abietio a·Acid_____ ｾｯ __f ....ｆ［［ＮＺｾｾ Ao i,ds_

0.1 o 0.2 o - 0.5 9.3 1.0 12.h 2.0 15.5 3. 0 18.7 4.0 19.5

Table VI AzeotroEic Pisti1lation wi ｾｾ ｊｾｾｴＺｚＺｬ J3ulE,hurlc Acid ($0 mIl in ｂ･ｮｺｾｮ･［ Distil for 20 Minutes and ｔｩｴｲｾ Wt Abi.etl0 Normality %Abietio Acid KOH Tttre Blank Aoid (gm) _.- (mIT TmlT

0;.9872 0.1978 28.3 15.6 78.05 1.0533 0.1978 30.0 15.0 82.9° 0.9961 0.1978 29.6 15.85 83.77 0.8407 0.1978 27.35 15.85 82.42 1.3100 0.1978 33.1 15.8 80.33 1.0522 0.1978 29.9 15.8 81.31

ＰＮＸＷＸｾ 0.1978 27.3 15.7 8°·M 0.870 0.1978 27.1 15·7 79. - 7 -

Table VII Usins AzeotroEic Distillation with 7$ ml Butanol + 75_ml Benzene wt Abietic %Acid Normality %Abietic Acid Catalyst KOH Titre Acid Comments -(gm) (mlf 1".4660 1.023 0.2064 19.4 82.J.t-7 10 min distillation 1.4714 1.019 0.2064 17.0 72.01 1.6423 0.913 0.2064 22.2 84.26 20 min distillation 1.5410 0.973 0.2064 20.3 82.11 1.J+942 1.ooJ+ 0.2064 20.4 85.1 30 min distillation 1;.6540 0.907 0.2064 22.2 83.66 40 min distillation 1.5856 ＰＮＹｾＶ 0.2064 20.7 50 min distillation 1.53°0 0.9 ° 0.2064 19.5 79.81·U

Slight variations in the procedure were made by using a mixture of 75 m1 of n-butyl alcohol and 75 ml of benzene and adding 1 ｰ･ｾ oent of conoentrated sulphuric acid, calculated on the weight of abietic acid. The mixture was distilled azeotropioally for various times, oooled and titrated. The results of this are shown in Table VII. Table VIII shows the results of a similar study made on linseed oil fatty aoids in whioh the additional variable of the quantity of oata1yst used was studied. It is seen from the limited stUdy undertaken that the degree of esterification is dependent upon the tine of esterification and the amount of oatalyst used. Thus the oonolusions made of the ａｓｾＴ method, with its limitations, are valid with Linder's method. It would therefore appear that a method not dependent on esterification for separation should produoe better results. There are several possible alternatives to produoe this separation, one of these being titration in non-aqueous solvent·.

Titrations in Non-aqueous ｓｯｬｶ･ｮｴｾ The method used was to dissolve the aoid mixture in a suitable solvent and to titrate the solution with a titrant potentiometrioally using a Beokmann pH meter with external e1eo• trodes. It was hoped that the resulting titration ourves would produce a separation but this was not the oase as is seen in Fig. 5. The variations used were:

1. Titrant: sodium methoxide Solvents: (a) benzene, (b) , (c) ether (d) dimethylformamide 2. Titrant: triethyl - n-butyl ammonium hydroxide - 8 -

The ourve for the titration in aoetone is shown in Fig. 6. Although all of these gave excellent results with the individual acids, they were not able to separate a mixture of the two.

Table VIII

ｾｴｲｯｰｩ｣ Distillation on Fatty Acids Using 75 ml Butanol + Z$ ml Benzene wt FattY' ｾ Acid Esterifi- Acid Catalyst Norma1itI Titre cation Time ｾ % {gm} • (m])" (min)

1.5040 Oe9Z? 0.189 24.9 12.11 10 ＱＮｾＸＱＹ 0.9 8 0.189 25.8 10 1. 747 1.017 0.189 23.7 ｾＺｾ 30 ＱＮｾｾＸ 1.007 0.189 1 .1 30 1. 0 1.825 0'.189 ｾＴＺｾ 21.21 20 1.5397 ＱﾷＮｾＴＸ 0.189 23.2 20.03 20 1.5799 2. 48 0.189 17.8 40•1 20 1.6625 2.707 ＰＮＱｾ 22.0 29.76 20 1'.5965 3.758 0.2 4 ·18.45 32.86 20 1'.5976 ｾＮＷＵＶ ＰＮＲＰＶｾ 17.9 34.89 20 ＵｾｍＡ .8Z? 0.2064 18.1 20 1:6l' 9 ＴＮｾ 0 0.2064- 16.1 roJ%3.2 20 1.5 98 9. Ｓｾ 0.2064- 9.0 7.11 20 ＱＮｾＰＶＹ 9.93 0.2064- 9·r 6 20 1. 6 1 10.231 0.2064- 0.5 74.26.33 30 ｬｯｾＶＲＰ 9.603 0.2064 7.5 72.10 30 1. 97 10.015 0.2064- 3.°5 88.16 1. 556 9.060 0'.2064 2.4 91.58 19

Conclusions and Recommendations There exist several sources of error in the proposed procedure. These are: 1) Incomplete esterification of the fatty acids; 2) Partial esterification of the rosin acids; 3) Loss of unesterified acids on extraction with Na2s04 solution used to remove the acid catalyst. - 9 -

The degree of esterification of the rosin and fatty acids has been shown to be dependent upon: 1) Amount of acid catalyst used; 2) Period of esterification; 3) Amount of sample used. It is impossible by straight titration to separate the two aoids'. Duo to the effeot of esterifioation there may be a larger titration of the fatty aoid than of the rosin aoids. If it is intended to persist with the proposed ASTM prooedure it is recommended that the Na2S04 wash should be omitted and replaced with a potentiometric double titration. Stmi1ar conclusions can be applied to the Linder method with the exception of those applied to the Na2S04 wash since this is absent in the Linder method. Finally it may be concluded that a method dependent upon esterifioation is undesirable. ｎｯｮＭ｡ｱｵｾｯｵｳ titrations have been tried without success. There are, however, other approaches such as ion exchange or ultra-violet speotrometry. With regard to the latter, Wolff (3) has separated the types of abietic aoid in this manner and similar work has been done by Harris and Sanderson (1).

REFERENCES 1. Harris, G.C. and T.F. Sanderson. aoids. I. An improved method of isolation of . Amerioan Chemical Society Journal, v. 70, P.334-339. 1948; and Resin acids. III. Isolation of dextroprimario acid and a new primaric-type aoid - isodextroprimaric acid, v. 70, p. 2079-81, 1948. 2. Linder, A. and V. Persson. Determination of rosin acids in mixtures with fatty acids. Journal of Amerioan Oil Chemist's Society, v. 34, p. 24-27, January 1957. 3. Wolff, J.P. Application de ia spectrophotometrie U.V. a l'etude des reslnes et terebenthines (Application of ultraviolet spectro• photometry to the study of and turpentines). Peintures, Pigments, Vernis, v. 34, n. 8, p. 346-355, August 1958. 12 • I I i I I Iii Iii t

o o rF 10 o o o o 8 o o

ｾＶ

4

TIME = 50 MINS. 2 CATALYST ACID CONTENT =0·5 0/0

I! 0' I v-I o 2 4 6 8 10 12 14 16 18 20 22 24 TITRE IN ML

FIGURE I POTENTIOMETRIC TITRATION OF ABIETIC ACID 100 I J\ d I is I I ｾ

80 z LEGEND 0 I! 0 ABIETIC ACID ｾ I d LINSEED OIL FATTY ACID 60r- 60 MIN ESTERIFICATION a: w .... 40 en w ｾ 0 20

o r , , ,: , , 2-0 4-0 6-0 8-0 10-0 0/0 ACID CATALYST (H2 S04) FI GURE 2 ESTERIFICATION VS ACID CATALYST 70 I, iii i •

l1 60

:::!E « a:: 50 C) LEGEND 0::: W a. o ABIETIC ACID z 40 6 LINSEED OIL FATTY ACID o 10% CATALYST .... « u ｾ 30 a::- ....w CJ) w 20 ｾ

10

o V I I , I I t 10 20 30 40 50 60 TIME IN MINS FIGURE 3 EFFECT OF TIME ON ESTERIFICATION PRODUCED PER GRAM 100 1 ! ｾ * T

80 z o LEGEND ｾ « 60 o ABIETIC ACID o Ii LINSEED OIL FATTY ACID LL 10% CATALYST 20 MIN ESTERIFICATION 0:: I.LJ .- 40 U) I.LJ oｾ 20

0' or , I , , 1·0 2-0 3·0 4·0 SAMPLE WEIGHT IN GRAMS FIGURE 4 EFFECT OF SAMPLE WEIGHT ON ESTERIFICATION 12 I 1 I I i I i I I i Iii

"10

8

I 6 0.

LEGEND 4 o ABIETIC ACID tJ. LI NSEED OIL FATTY ACID D 50/50 MIXTURE OF ABIETIC ACID AND FATTY ACID 2

o I,,,,,II,,I ,, 2 4 6 8 10 12 14 " 16 18 20 22 24 TITRE IN ML

FIGURE 5 NON - AQUEOUS TITRATIONS OF SODIUM METHOXI DE IN BENZENE + 100 rl ------1'------.....,-'------.,.,------.i

o

-100

-200 > E z -300 ..J

-600

-700 .0--.0--0

-800' I I , , o 5 10 15 20 TITRANT IN ML

FIGURE 6 TITRATION CURVE FOR LINSEED OIL FATTY ACID/ABIETIC ACI D WITH TR I ETHYL- N- BUTYL AMMONIUM HYDROXIDE APPENDIX A

A.S.T.MIt PROCEDURE FOR TOTAL ROSIN CONTENT OF COATING IlJJ\TERIALS

(8) Transfer to a 500-ml Erlenmeyer flask an amount of sample containing approximately 40 ± 2 gill of nonvolatile material. Weigh the sample used to the noarest 0.1 gm. Add 150 ml of the ethylene glycol solution of KOH, and swirl to disperse the sample. Add a boiling stone, attach the air condenser, and reflux on 8 hot plate for 2 hr. (b) At the end of the 2-hr refluxing period, remove the solution from the hot plate and cool to room temperature under tap water. Add 100 ml of water, and while cooling under tap water, add 40 m1 of HCl'. Place on the hot plate again, reflux for 5 min, and cool under tap water. (c) Transfer the sample quantitatively to a I-liter separatory funnel with the aid of a total of 150 ml of water, followed by two 30-ml rinses of benzene. Mix, allow the layers to separate, and draw off the lower aqueous layer into a second I-liter separa• tory funnel. Extract the aqueous layer with two successive bO-ml portions of benzene, and drain the aqueous layer into a third I-liter separatory funnel. Combine the benzene extracts, and wash with three 30-ml portions of water. (d) Transfer the washed benzene extract to a 400-ml beaker with the aid of a total of 25 ml of benzene. Add a boiling-stone, and evaporate the benzene on a steam bath. (0) Transfer the residue to a 500-reI Erlenmeyer flask with the aid of a total of 100 ml of methanol, add a boiling stone, and swirl to dissolve the oil. Slowly add 5 ml of H2S0Jl while cooling under tap water. Connect the flask to the condenser and reflux on the hot plate for 10 min. Cool to room temperature under tap water. (f) Add about 250 ml of the Na2S01J. solution to a I-liter separatory funnel. Pour the contents of the flask into the funnel, and complete the transfer with 100 ml of benzene. Shake thoroughly, allow to settle, and draw off the salt layero Wash the benzene layer again with two successive 250-ml portions of the salt solution. The last wash should be neutral to mothyl or3ngGi otherwise continue the washing with 50-ml portions of Na2S04 solution until neutrality is obtained. A-2

(g) After removing the last wash, draw off the benzene layer into a 400-ml beaker, using a total of 75 ml of ethanol to complete the quantitative transfer. (h) Complete the determination by the indicator method or by the potentiometric method.