ANALYTICAL CHEMISTRY. 1049 Published on 01 January 1909

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ANALYTICAL CHEMISTRY. 1049 Published on 01 January 1909. Downloaded 27/10/2014 11:46:05.

Analytical Chemistry.

A Device for Preventing Over-Titrating, FERDINANDSCHULZ (Chem. Zeit., 1909, 33, 11S7).-In the liquid to be titrated is placed an open tube about 12-15 mm. in diameter, and the titration is carried out as usual whilst rotating the beaker. The column of liquid inside the tube has, however, not yet been acted on, so by using the tube as a stirrer, the two liquids mix and any over titrstion wili be again neutralised. The last drops of the volumetric solution are then added very cautiously. L. DE h View Article Online

1050 ARSTK. ACTS OF CHEMICAL PAPERS. Porcelain Gooch Crucibles with a Layer of Spoiigy Platinum. HENRIJ. F. DE VRIES(Chem. Weeeekblccd, 1909, 6, 816-818. Compare Abstr., 1907, ii, 504, 719 ; 1908, ii, 430, 534 ; Brunck, this vol., ii, S26).-A claim for priority. The crucible described by Brunck has been employed by the author for two and a-half years. The method of preparing the platinum layer is described. A. J. W. Detection of Traces of Chlorides in Gelatin. LUPPO-CRAMER (Zeitsch. Chem. Ind. Kolloide, 1909, 5, 249--250).--The smallest trace of chloride can be detected in gelatin if a 10% solution is dried on a glass plate, and a drop of 10%silver nitrate placed thereon. Sodium chloride present to the extent of 0.001% of dry gelatin gives a white ring, 1-2 cm. in diameter, round the drop. The reaction Ban be used quantitatively if standards asre made from chloride solutions and carefully wmhed gelatin. On exposing the gelatin film so treilted to light, the ring turns bluish-, and the colourless space under the drop reddish-yellow. This indicates that silver chloride is present in both, but in a finer state of subdivision in the latter. The author has shown that the thickening (" reifung ") of the haloid salts in a gelatin plate is due to excess of halogen, and not to excess of silver. The ring is formed where the diffusing colloidal silver chloride arrives at a region where halogen is in excess. G. S. W. The Presence of Iodate in Commercial Potassiuni Iodide. LAUNCELOTW. ANDREWS (J. Amer. Chem. Soc., 1909, 31,1039-1039). -The author states that the general belief as to the presence of iodate in commercial potassium iodide is not justified, and that if any is present its amount cannot exceed 20 parts per million. The blue colour which some samples give on adding starch paste and dilute

Published on 01 January 1909. Downloaded 27/10/2014 11:46:05. hydrochloric acid is not necessarily due to iodate, but may be due to traces of iron oxide or cuprous oxide in presence of dissolved oxygen. Potassium hydrogen tartrate in solutions free from air does not give the reaction with those impurities, and is therefore preferable to hydrochloric acid. A convenient arrangement for carrying out the test is described. L. DEK. Photo-electric Measurement of Small Ozone Concentra- tions. Efficiency of Goldstein's Ozonisation Process at Great Dilutions. WILHELMHALLWACHS (Ann. Physik, 1909, [iv], 30, 602--606).-1t is shown that small quantities of ozone can be estimated photo-electrically by reason of the large specific absorptive power of the gis for ultra-violet radiation of wave-length in the iieighbourhood of 258pp. For such measurements the pressure of the gas in t.he absorption tube should be of the order of 0.01 mm. of mercury. Attempts to prepare ozone from oxygen by Goldstein's process indicated that this process is ineffective at very low pressures. H. M. D. Bulb Trap for Nitrogen Estimations by the Methods of Kjeldahl and Others. FR. DUDY(Chem. Zeit., 1909, 33, 1158)- By using the following arrangement, all danger of any alkaline View Article Online

ANALYTICAL CHEMISTRY. 1051

liquid from the distilling flask getting into the standard acid is avoided. A is a cylindrical tube of a suitable diameter. At a it has an opening of "1 mm., and at b, one of 5 mm. To the cylinder is sealed the funnel-shaped tube c, which has a diameter of about 5 mm. Bis the usual bulb. On account of the great width of the tube A, a wide piece of rubber, not too thin, is used to connect the tube to the distilling flask. L. DE K. Estimation of Total Nitrogen by the Rober Method. F. W. GILLand HARRYS. GRINDLEY(J. Amer. Cl~em.Xoc., 1909, 31, 1249-1252. Compare Sebelien, Brgnildsen, and Haavardsholm, this vol., ii, '757). - Kober (Abstr., 1908, ii, 776) has described a modification of the Kjeldahl method, in which the ammonia is expelled by adding excess of alkali, and passing a A current of purified air through the solution. Experi- ments have now been carried out which show that the process is well suited to the estimation of nitrogen in organic materials, except when magnesium and phosphorus are both present in comparatively large quantities. In the latter case, the total nitrogen can be accurately estimated if the solutions are kept warm during the passage of the current of air. E. G. Estimation of Nitrogen in Nitrates and Nitrites. VINCENTSCHENKE \Clmn. Zed., 1909, 33, 1203).-A rep17 to Mitscherlich (Abstr., 1909, ii, 614). Contrary to Mitscherlich s statement, the author remarks that nitrates may be completely Published on 01 January 1909. Downloaded 27/10/2014 11:46:05. reduced in acid solution. L. DE E(. Detection of Nitrates in Presence of Oxidising Substances (Chlorates, Bromates) and Iodides and Bromides. 11. EMMANUEL POZZI-ESCOT(Ann. Chim. anaZ., 1909, 14, 413-414 ; Bull. Assoc. Chim. Sucr. Dist., 1909, 27, 367--368).-The solution containing the above salts is introduced into a distilling flask with a large excess of sodium hydroxide. The flask is fitted with a cork, through which passes a large tube bent at right angles. (If ammonium salts should be present, the ammonia should be completely expelled by boiling.) Two or three grams of zinc dust are added, and the whole is boiled gently, The vapours are received in a conical flask containing Nessler solution, and the least trace of nitrates will then be detected by the brown coloration. L. DE K. Irregularities in the Titration of Arsenic after Previous Dis- tillation. LEOPOLDBXANDT (Chem. Zeit., 1909, 33, 11 14-1 115).- The process generally used for the estimation of arsenic in iron ores or steel (conversion into ferric sulphate by evaporation with nitric and sulphuric acids, and distilling the dry mass with fuming hydrochloric acid with addition of ferrous sulphate) is attended with a number of View Article Online

10.5 2 ABSTRACTS OF CHEMICAL PAPERS.

slight errors, which may, however, be readily avoided. No condensing apparatus should be used, but the delivery tube, carrying a bulb and drawn out to a narrow point, dips into a large beaker containing water, which completely absorbs the acid fumes, and, consequently, the arsenic chloride ; the beaker is kept cool by being placed in a larger beaker containing cold water. When distillation is finished, the contents of the beaker are neutralised with ammonia free from pyrrole ; sodium hydroxide cannot be recommended on account of such frequent impurities as nitrites, chlorates, etc. After adding solution of sodium hydrogen carbonate, the arsenic is titrated with N/lO-iodine, using 5 C.C. of a 2% freshly prepared starch solution as indicator; starch containingzinc iodide as preservative must not be used, as this causes precipitation of zinc arsenite. Pyrrole-free ammonia may be read.ily obtained by tinging ammonia with permanganate, and afterwards decanting from the deposit formed. L. DE K. Electrolytic Detection of Arsenious Oxide in Presence of Arsenic Acid. ERCOLECOVELLI (Chem. Zeit., 1909, 33, 1209)- Thirty C.C. of the liquid to be tested are mixed with excess of potassium hydroxide and placed in a U-tube, into the limbs of which are placed two platinum foils, which are connected with the poles of a Grove cell. In the cathode limb is suspended a strip of paper impregnated with silver nitrate, and if arsenious oxide is present, even in fractions of a mg., a decided brown coloration will be noticed in a time varying from a few minutes to an hour. Arsenntes are not affected. L. DE K. The Detection of Arsenic Acid in the Presence of Arsenious Acid by means of Magnesia Mixture. OSCAR LUTZand R. SWINNE(Zeitsch. ccnorg. Chern., 1909, 64, 298-30 l).-Arsenious acid has been stated to give a magnesium salt which is not readily separated Published on 01 January 1909. Downloaded 27/10/2014 11:46:05. from the arsenate. Experiments with solutions of different concentrations show that a qualitative or quantitative separation is not possible, although the precipitation of the arsenite is greatly hindered by the presence of large quantities of ammonium salts. Under these conditions, however, the precipitation of the arsenate also becomes incomplete, C. H. D. Analysis of Orpiment. M. CAFFIN (Collegium, 1909, 26, 225-22 6).-An application of Pearce’s method for estimating arsenic in minerals, The substance is fused with potassium nitrate and sodium carbonate, whereby sulphur is oxidised to sulphuric acid and arsenic to alkali areenate. The solution is made up to a convenient volume, the arsenic precipitated and colle’cted as silver arsenate, redissolved, and titrated with ammonium thiocyanate. Sulphur is estimated as barium sulphate in a different portion of the original solution. F. M. G. M. Modiilcation of the Reduction Process for Copper Spirals Used in Organic Combustions. ADRIANOOSTROGOVICH (Chem. Zeit., 1909, 33, 1187).-The red-hot spirals are introduced quickly into a View Article Online

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long tube made of hard Jena glass open at one end. At the bottom is placed a little asbestos, which is moistened with a little metbyl alcohol. A perforated cork fitted with a glass tube is inserted, and the tube connected with a pump, which is kept working until the tube has quite cooled down. The spirals will then be found to have been completely reduced. L. DE K. Replacement of the Platinum Capillaries in the Est-imation of Carbon in Iron by the Chromic Acid Method. MAX WIDEMANN(Chenz. Zeit., 1909, 33, 1186).-The author dispenses with the platinum capillaries, but uses instead a silica tube 30 cm. long and 10 mm. in diameter, the walls being 1 mm. thick, which is filled with platinum cuttings. The tube is placed on an asbestos felt and heated with a Heinz burner. A complete combustion of any hydrocarbons is thus secured. L. DE K. Rapid Estimation of Sodium Hydrogen Carbonate in Presence of Sodium Carbonate. BERTHOLDLOWINGER (C’hern. Zeit., 1909, 33, 1174).-A solution of sodium hydroxide is mixed with a little barium chloride to remove any carbonate, and the liquid is then at once standardised with hydrochloric acid, using phenolphthalein as indicator. To the solution to be examined is then added a definite volume of the standardised alkali, and the sodium carbonate formed from the acid carbonate plus that pre-existing is then precipitated by adding barium chloride. The alkalinity is then taken as before and the difference in the titrations represents the sodium hydrogen carbonate. L. DEK. Estimation of Calcium Oxide in Presence of Calcium Carbonate, etc. HEYER(Chem. Zeit., 1909, 33, 1157-115S).-

Published on 01 January 1909. Downloaded 27/10/2014 11:46:05. Calcium oxide may be separated from calcium carbonate by means of a 176 solution of ammonium chloride or nitrate, to 1 litre of which 48 C.C. of ammonia, D 0.9 10, have been added. If no free ammonia is added, a small portion of the carbonate also dissolves. The results are sufficiently accurate for technical purposes. L. DE I(. Estimation of Magnesium Chloride in Waters. HERMANN EMDEand RICHARDSENST (Zeitsch. angew. Chem., 1909,22,2236--2238. Compare Abstr., 1909, ii, 940).-A further series of experiments proving conclusively that, on heating magnesium salts with chlorides at 500--520°, magnesium chloride is formed, and a loss of chlorine consequently takes place. Pfeiffer’s method, which is based on the decomposition of pre-existing magnesium chloride by heat, is therefore quite untrustworthy. If heated at a lower temperature, the decomposition of magnesium chloride is incomplete. L. DE K. Estimation of Zinc as Pyrophosphate. RALPHW. LANGLEY (J.Amer. Chem. Soc., 1909, 31, 1051-1052).--8 simplification of the process usually employed. To the zinc solution, which should be made neutral to litmus by means of ammonia, is added an excess of ammonium phosphate. After heating for some time on a steam- View Article Online

1054 ABSTRACTS OF CHEMICAL PAPERS.

bath, the precipitate is collscted on a porcelain Gooch crucible, washed five times with cold water, and ignited to constant weight. L. DE K. Volumetric Estimation of Lead with Potassium Per- manganate. HERMRNNBOLLENBACII (Chem. Zeit., 1909, 33, 1 142-1 143).-A slight modification of the author’s previous process. The lead solution is poured into a hot alkaline Folution of potassium permsnganate, standardised by means of lead nitrate, and the excess of permanganate is then titrated with the same lead solution (compare Abstr., 1908, ii, 68). In order to cause the precipitate formed to settle more rapidly, an addition was made of some barium sulphate. This, however, has since proved to be unsatisfactory, and addition of 2 to 5 grams of potassium nitrate is now recommended. L. DE K. An Application of Graded Potentials to Ore Analysis. DANIELF. CALHANEand J. C. WOODBURY(J. dmw. Chem. Soc., 1909, 31, 1048---10~1).-A process devised for analysis of nntive lead carbonate, containing also a little silver and copper, besides other impurities, Two grams of the sample are dissolved in nitric acid, and, after neutralising the liquid, 30 C.C. of nitric acid, D 1.42, are added, and the whole is diluted to 250 C.C. Twenty-five C.C. are then taken for analysis by electrolysis. With an E. J4.F. of exactly 1.4 volts,.the silver is-deposited after two hours, and may then be weighed. The electrolysis is then continued overnight at 2 volts, so as to obtain the copper and the lead, which is precipitated as peroxide on the anode. It is very important that the voltage should never exceed 2 during the operation, as otherwise the deposition of the lead peroxide and the copper is incomplete.

Published on 01 January 1909. Downloaded 27/10/2014 11:46:05. L. DE K. Electrolytic Estiniation of Thallium. GILBERTW. MORDEN(J. Amer. Chern. sbc., 1909, 31, 1045-1048).-Thallium may be estimated electrolytically by using a mercury cathode and rotating anode, but it is advisable to use, instead of pure mercury, a very dilute zinc or cadmium amalgam. A stable non-oxidisable thallium amalgam is thus obtained. L. DE K. Estimation of Cuprous Oxide in Copper and its Alloys. RICHARDHENRY GREAVES (Chem. LVews, 1909, 100, 233--235).--The estimation of cuprous oxide by solution in ammonia as described in the method proposed by Coffetti (this vol., ii, 349) was found to give trustworthy results in the case of pure copper. When arsenic is present, the results are too high, but an approximate correction may be calculated from the amount of arsenic dissolved, on the assump- tion that it dissolves as arsenate; the same applies to antimony. Commercial copper contains, however, but little, if any, antimony or iron, and errors resulting from the presence of these two metals will be small in practice. The process may be applied to brass and bronze, but, in the case of the latter, the method is not of much use, as the View Article Online

AX’ALYTICATA CIIEMISTRP. 1055

oxygen exists mainly as metastnnnic acid, and it is this substance which exerts the deleterious influence on the properties of the alloy. The author employs a modification of the apparatus described by Coffetti; instead of a vertical tube, a horizontal one is used. The metal is introduced through a side-tube at the middle of the main tube, this side-tube also serving as the inlet for the ammonia solution after the apparatus has been filled with hydrogen saturated with ammonia. A tube at one end of the main tclbe serves for the intro- duction of the hydrogen, whilst one at the other end acts as an outlet for the gas and liquid. w. P. s. Detection of Mercury in Urine according to AlmBn. CONRADSTICH (Pha?*rn. Zed , 1909,54, 833).-In -4lmBn’s process the urine is boiled with sodium hydroxide and dextrose, and the precipitate, which contains all the mercury, is then boiled with hydrochloric acid and a piece of copper or brass wire. This, on being heated in a narrow glass tube, gives a sublimate of metallic mercury, which may be recognised as such under the microscope. The author prefers using very thin pieces of copper foil instead of the wire. These are heated afterwards on the convex part oE an object glass, on which is placed another object glass to receive the mercurial sublimate. This may be further identified by placing it over another object glass, on the convex part of which a drop of tinc- ture of iodine has been allowed to evaporate. Soon the mercury is changed to the iodide, which has a characteristic appearance under the microscope. By using “standards,” an idea as to the amount of mercury present may be obtained. L. DE K. Estimation of Iron in Water. KLUT(Chem. Zentr., 1909, ii, 1076-107 7 ; from Mitt. K. Pruygs.-Anst. Vusseruersorg Abwassevbeseit,

Published on 01 January 1909. Downloaded 27/10/2014 11:46:05. 1909, 12, 174--182).-Five hundred to one thousand C.C. of the sample are concentrated to 150-200 c.c., and boiled with 2-3 C.C. of strong nitric acid. Theiron is then precipitated with ammonia, washed, and redissolved in hydrochloric acid. It is estimated colorirnetrically by means of ferrocyanide, or, preferably, thiocyanate. The process does not work well with waters charged with peaty matter ; in this case, the organic mattersmust be got rid of by burning. L. DE I(. Rapid Estimation of Vanadium in Ores and Technical Products. EUGENIOPIREROA ALVAREZ(Chenz. Zeit., 1909, 33, 1149).-The finely-powdered material (about 0.5-1 gram) is fused with seven to eight times its weight of pure sodium peroxide for fifteen to twenty minutes at a red heat. When cold, the mass is treated with boiling water and the filtrate acidified with sulphuric acid. Alcohol is then added, and, without taking notice of any precipitate, a current of sulphur dioxide is passed for some time. Any undissolved matter is removed by filtration, and the liquid is freed from alcohol and excess of sulphur dioxide by heating and passing a current of carbon dioxide. If arsenic should be present, this must be removed by means of hydrogen sulphide, and, after boiling the filtrate View Article Online

10.56 ABSTRACTS OF CHEMICAL PAPERS.

to expel the excess of that gas, the vanadium is titrated (in a 1% solution) with standard permanganate. This should be checked with a 1% solution of ammonium metavanadate, after first expelling the ammonia with sodium hydroxide and then reducing the solution by boiling with sulphuric acid ancl sulphur dioxide under similar conditions to those described. L. DE K.

Assay of Oil of Turpentine by Bromine; Estimation of Free Bromine by Sodium Formate. MANSIER(Am. Chim anal., 1909, 14, 417--421).--0ne C.C. of the sample is placed in a stoppered flask and dissolved in 5 C.C. of chloroform; 50 C.C. of 3% bromine water are then added at once, and the whole is well shaken. More bromine water is added with constant shaking until the last drop causes the cliloroform to turn yellow. One C.C. of pure oil of turpentine absorbs 1.69 grams of bromine. If less is required, the presence of petroleum may be suspected and its amount calculated. A new method is given for checking the bromine solution ; 10 C.C. of sodium formate (1.6125 grams per litre) are placed in a flask, and 0.10 gram of precipitated zinc oxide is added. The bromine solution is then run in until the liquid turns yellow. One mol. of sodium formate = 2 atoms of bromine. On account of the action of bromine on zinc oxide and the amount required to colour the water, a correction of 0.01s gram must be applied. L. DE K.

[Estimation of Phenol and p-Cresol in Urine.] W, MOOSER (Zeitsch. physiol. Chsrn., 1909, 63,155--200).-See this vol., ii, 1039.

Ultramicroscopical Studies, J. AMANN(Chem. Zentr., 1909, ii, Published on 01 January 1909. Downloaded 27/10/2014 11:46:05. 1076 ; from Schweiz. JVoch. Chem. Pharm., 1909, 47, 480--483).-The reduction of Fehling’s solution, observed under the ultramicroscope, is a neat and delicate reaction, it being obtainable with a solution containing 0-00001 gram of dextrose per C.C. The Fehling solution of the Swiss Pharmacopaeia, which contains glycerol, cannot, however, be used in this case; the formation of osazone by means of phenyl- hydrazine is also readily observed by means of the instrument. L. DE I(.

Clinical Detection of Dextrose in Urine by o-Nitrophenyl- propiolic Acid. H. BOTTU(Chem Zmt~.,1909, ii, 1280 ; from Bull. Xci. Pliurmacol., 1909,16,399-401).-3*5 Gramsof powdered o-nitrophenyl- propiolic acid are dissolved in 50 C.C. of 10% sodium hydroxide and diluted to lO00c.c. Eight C.C. of the reagent are mixed in a test-tube with 20-25 drops of urine, and the upper layer is heated to boiling. Another 1 C.C. of urine is then added drop by drop. In the presence of dextrose a blue coloration and precipitate, due to indigotin, will be noticed. If the blue colour appears before the second portion of the urine js added, the amount of dextrose is sure to exceed 1%. L. DE K. View Article Online

ANALYTICAL CHEMISTRY. 1057

Detection of Biliary Acids, Laevulose, Glycuronic Acid, and Pentoses in Urine. F. WITTELSand N. WELWART(Chem. Zeit., 1909, 33, 1133).-An adverse criticism of Jolles’s proposed modifica- tions (compare ibid., 1908, 32, 917) of the Ihl-Pechmann’s process for the detection of lsvulose, of Tollens’s glycuronic acid test, and Bid’s pentose reaction as applied to urines. LTheoriginal methods are recommended. L. DE K.

Estimation of Carbohydrates in Foods. P. C. DEN HERDEB (PI~nrm.Feekbkcd, 1909, 46, ;1306--1312).-1n no case should the balance in the analysis of food products be called starch; starch should be estimated in the residue insoluble in cold water by inversion with 2% hydrochloric acid. Sugar should be inverted by Clerget’s process, for, if inverted by boiling, a very serious loss (up to 30%) may occur. There is generally a deficit in the full analysis, but this may be checked to some extent by determining the portion soluble in cold water (freed from albumin) and allowing for sugars present; in a well-conducted analyses the residue should be fairly equal to the deficit in the full analysis. For the separation of dextrin and soluble starch, it is recommended to evaporate the aqueous solution, obtained in due course, to about 10 C.C. ; the dextrin, etc., is then precipitated by first adding 40 C.C. of methyl alcohol and then 160 C.C. of 95% ethyl alcohol. The alcoholic solution retains the sugars. In these kind of analyses, it is advisable first to make a qualitative analysis; the operations may then very often be considerably shortened. L. DE I<.

Direct Detection of Formaldehyde in Leaves; Formaldehyde Reagents. THONASBOKORNY (Chem. Zeit., 1909, 33, 114 1-1 142, Published on 01 January 1909. Downloaded 27/10/2014 11:46:05. 2150--1151).-A review of the various reagents proposed for the detection of formaldehyde, and of the attempts made up to the preseut to apply a direct microchemical test for that substance in leaves in which, according to recent theory, it is supposed to occur as an intermediary compound. The author remarks that the reagents used are either too caustic or else too poisonous. The leaf, being killed, cannot go on gonerating formaldehyde, and the quantity already present is too small to be detected with certainty. It is also doubtful whether the distillation process yields better results. L. DE II(. Estimation of Foynlic Acid. HARTWICFRANZEN and G. GREVE(J. pr. Chern., 1909,[ii], 80, 368-389).-Gravimetric methods, based on the reduction of mercuric chloride by formic acid, only yield quantitative results when the hydrochloric acid formed during the reaction is neutralised as the reduction proceeds ; if this is done, the amount of mercurous chloride precipitated is equivalent to the quantity of formic acid present. The method is applicable to the estimation of formic acid in very dilute solution iE the following details as to procedure are carried out. The formic acid solution, containing from 0.2 to 1.0 gram of the acid per litre, is treated with mercuric chloride View Article Online

1058 ABSTRACTS OF CHEMICAL PAPERS.

dissolved in hot water, the quantity added being fifteen times the amount required by the equation : HC0,H + 2 HgCl, = CO, + 2 HC1+ Hg,CI,. The mixture is maintained at a temperature of about 100’ for thirty minutes, then neutralised by the addition of sodium hydroxide solution, again heated for about thirty minutes: and once more neutralised. The neutralisation is carried to the point where mercuric oxide begins to be precipitated. When the precipitate of mercurous chloride has settled completely, 20 C.C. of concentrated hydrochloric acid are added to re-dissolve the mercuric oxide; the heating is continued for one hour, and the precipitate is then collec!ed on a weighed filter; it is mashed with hot water, dried for six to eight hours at looo, then kept in a vacuum for about fifteen hours over sulphuric acid and potassium hydroxide, and weighed. The weight of the precipitate multiplied by 0 097726 gives the weight of the formic acid present. It is also shown that formic acid may be removed from a solution by steam-distillation in the presence of phosphoric acid. The distillation must be continued until 10 C.C. of the distillate do not require more than half a drop of N/lO-barium hydroxide solution for neutralisation, w. P. s.

Volumetric Estiiiintion of Thiocyanic Acid with Pernian- ganate ; its Application to Volumetric Estimation of Copper. G. MASINO(Chem. Zed, 1909, 33, 1173-1174, 1185--1186).-An investigation of the permanganate process for the estimation of thiocyanic acid and indirect estimation of copper. The author confirms the results: obtained by Klason, and by Grossmann and Holter, which showed that thiocyanic acid is not oxidised quantitatively by permanganate, a residue being left,, the amount of which increases with the dilution. If,in order to avoid this, solutions of greater concentration are used, a still greater source of error is introduced, owing to the Published on 01 January 1909. Downloaded 27/10/2014 11:46:05. difficulty of accurately measuring the liquids. In using this process, the standardisations and the actual analysis should, therefore, be carried out under exactly similar conditions. Hydrochloric acid solutions are preferred. L. DE K.

Estimation of Salicylates. ATHERTONSEIDELL (J. Arrze~. Chm. Soc , 1809, 31, 1168--1178).-After criticising unfavourably the bromate method of Freyer, and the iodine method of Meseinger and Vortmann, the author proposes the following process. The ealicylate is added to a known volume of standardised Solution of bromine in strong hydrochloric acid, which causes the salicylic acid to be precipitated completely as a dibromo-compound, and the excess of bromine is then titrated with standard stannous chloride as usual. L. DE K.

Silver Cyanamide. I€. RUSSELLELLIS (Cllem. News, 1909, 100, 154--155).--In Perotti’s methcd for the estimation of cyanamide in sodium cyanamide and in “nitrolime ’’ (Abstr., 1905, ii, 870), any sulphide, cyanide, or chloride which may be present as impurity is thrown down with the cyaqamide in the precipitation with silver nitrate, and an incorrect result is cibtained. View Article Online

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The author puts forward the following methods : 1. Estimation of cyanamide and cyanide in sodium cyanamide.-From an aqueous solution of the substance, the cyanide is precipitated by excess of silver nitrate in the presence of nitric acid. After washing the precipitate of silver cyanide, it is dissolved in nitric acid, and the silver estimated by titration with ammonium thiocyanate. The filtrate and washings from the silver cyanide are run into a slight excess of ammonium hydroxide solution and the solution warmed. A precipitate of silver cyanamide is obtained ; this is dissolved in nitric acid, and the silver estimated by titration. From the silver in each case, the percentage of cyanide and cyanamide can be determined. 2. Estimation of “Nitrolime.”-One to two gramsof the finely powdered substance are shaken up with water, and filtered into a 500 C.C. flask, the residue being well washed until the filtrate gives no precipitate with ammoniacal silver nitrate solution. An aliquot portion of this solution is precipitated by excess of ammoniacal silver nitrate. The precipitate is well washed with warm water, and then treated with dilute nitric acid (1 : 5), in order to remove all the silver cyanamide. The silver in the filtrate and washings is then estimated by titration. Any sulphide or chloride of silver remains on the filter paper. Any fluoride present in the cyanamide will not dissolve in water, or if any dissolves, it is not precipitated. The above methods assume that silver cyanamide has the formula Ag,CN,. To verify this, the pure salt was prepared from ‘‘ nitrolime ” and analysed. The percentage of silver was determined (a) by heating, and weighing the silver left, (b) by dissolving the salt in nitric acid and estimating the silver with ammonium thiocyanate. The results are in agreement with tho formula Ag,CN,, and not with AgHCN,, although the two methods do not give the same percentage of silver- 84.48 in (a) and 83.3 in (b). Published on 01 January 1909. Downloaded 27/10/2014 11:46:05. When silver cyanamide is heated, it explodes more or less violently. The gases formed by the explosion were found to be cyanogen and nitrogen. Quantitative estimations indicated that the decomposition occurs in accordance with the equation : 2Ag,CN, = 4Ag + C N + N,. k2s.P. The Detection and Method of Formation of Aromatic Substances in the Organism. I. Detection of Indole and Scatole. FERDINANDBLUMENTHAL, ERIEDRICH HERSCHMANN, and ERNSTJACOBY (Biochem. Zeitsch., 1909, 19, 521--533).-The various reactions for the identification of indole and scatole were investigated. The p-dimet hylaminobenzaldehyde reaction can be employed to dis- tiaguibh between the two substances if nitrite is added. Scatole on addition of nitrite gives a bluish colour, whereas indole gives a more orange colour. By this reaction indole and scatole can be detected in mixtures. The other reactions investigated were (a) the vanillin reaction, which is not suitable for detecting the two substances when both are present ; (b) the p-nitrobenzaldehyde reaction, by means of which both can be detected when scatole is present in relatively high concentration ; and (c) the protocatechualdehyde reaction, which is not applicable for detection of the mixtures; the heliotropin, the View Article Online

1060 ABSTRACTS OF CHEMICAL PAPERS.

safrole, cinnamaldehyde, eugenol, glyoxylic acid and other reactions were also investigated. s. B. s.

Chemistry of Urine. L. DE JAGER(Zeitsch. physiol. Chem., 1909, 62, 333-346).-This paper treats of two subjects: (1) the boiling test for albumin in urine, and its fallacies, especially in relation to the reaction of the urine, and the precipitability of certain phosphates on heating, and (2) the incorrectness of ammonia, estimations by the ‘‘ formaldehyde method ” recently introduced ; as others have pointed out, amino-acids also react with the reagent. W. D. H. Volumetric Estimation of Caseinogen in Cow’s Milk. EDWINE. HART(J. Biol. Chem., 1909, 6, 445-451).-The caseinogen is precipitated by acetic acid, washed on the filter with cold water, then returned to the flask with the filter, dissolved in N/lO-potassium hydroxide diluted with water free from carbon dioxide, and titrated with N/lO-acid, using phenolphthalein as indicator. A correction is made for the acidity of a blank experiment, and the amount of acid used is a measure of the quantity of caseinogen. The whole process occupies less than two hours, W. D. H.

Employment of Hydrogen Peroxide in Investigations on Oxydases. T. KIKKOJIand CARL NEUBEBG(Biochem. Zeitsch., 1909, 20, 523--525),-The employment of hydrogen peroxide and iron salts for the detection of oxydases is often resorted to. The authors show that phenol and twenty-five other substances, of which a list is given, yield, in presence of iron salts with the peroxide, dark colours or precipitates. The pigmented substance from phenol was prepared in quantity, and dieered from melanins in that it contained 3 2*60-14.38% Published on 01 January 1909. Downloaded 27/10/2014 11:46:05. iron. S. B. S.

A Reaction for Acid Soils. OSCAR LOEW(Zeitsch. Zandw. Versucltswesen Oestew., l909,461--463).-The soil (10 grams) is heated on a water-bath for five to ten minutes with 10 C.C. of a 1% solution of potassium iodide. A few drops of a 1% solution of potassium nitrite are added, adthen a few drops of starch solution, after which it, is quickly cooled. The blue coloration may sometimes be produced in absence of potassium nitrite with soils containing basic ferric salts (a very intense reaction was obtained with so-called colloidal ferric hydroxide which contained basic ferric chloride). The presence of basic ferric sulphate in such soils can be established by extracting several times with boiling water, digesting with ammonia, evaporating the ammoniacal filtrate, and treating with barium chloride aiid hydrogen chloride. N. H. J. M. J-