1917] AGRICULTURAL CHEMISTRY AGROTECHNY. 415 



as possible from water by draining, dissolved in 100 cc. of 90 per cent alcoliol, 

 and the araciiidic acid separated by crystallization. 



The procedure has been found capable of detecting 5 per cent of peanut oil 

 In olive oil, cotton-seed oil, soy bean oil, and corn oil. No attempt, however, has 

 been made to apply it for quantitative purposes. 



The deterraination of citric acid in milk, R. Kunz (Arch. Chem. u. Mikros., 

 8 {1915), No. 4, pp. 129-133). — The following procedure for the determination 

 of citric acid in milk, based on the test described by Stahre,^ is described : 



Fifty cc. of milk is treated with 10 cc. of dilute sulphuric acid (1:1) in a 

 200-cc. volumetric flask, and thoroughly shaken. Two cc. of a 40 per cent 

 potassiiun bromid solution and 20 cc. of a solution of phosphotungstic acid are 

 then added and the mixture made up to volume with distilled water. After 

 thorough mixing the precipitate is separated by filtration, 150 cc. of the perfectly 

 clear filtrate is transferred to an Erlenmeyer flask, 25 cc. of freshly prepared 

 saturated bromin water added, and the mixture then placed for about five 

 minutes on the water bath at a temperature of from 48 to 50° C. Ten cc. of 

 a 5 per cent potassium permanganate solution is then slowly added from a 

 pipette in a continuous stream with constant shaking of the mixture. The 

 pentabrom acetone which is precipitated is filtered and treated as previously 

 described for the determination of citric acid in wine.' 



A correction for the volume of the protein precipitated in the procedure de- 

 scribed for milk is necessary, and was found by the author to be such that 

 150 cc. of the clear filtrate used was equivalent to 38.2 cc. of the original sample. 

 Analytical data obtained from a number of samples of normal milk examined 

 showed a variation of from 0.1553 to 0.173 gm. of citric acid per 100 cc. of milk. 



In two samples of human milk examined, 0.0618 and 0.0439 gm. of citric acid, 

 respectively, were found per 100 cc. of milk. 



Comparative determinations of fresh and soured milk indicated that the citric 

 acid gradually disappeared with the aging of the sour milk. This destruction 

 of the acid is deemed to be due rather to microbial action than to the enzyms 

 contained in the milk. An examination of freshly prepared 24-, 48-, and 

 72-hour-old Bulgarian sour milk (yoghourt) showed no destruction of the citric 

 acid present. 



The determination of gum and pectin in filter residues [in the manufac- 

 ture of sugar], T. van deb Linden (Meded. Proefstat. Java-Suikerindus., 6 

 (1916), No. 7, pp. 205-219). — After some preliminary experimentation the fol- 

 lowing modified procedure for pectin determination was evolved : 



Twenty gm. of the residue is digested for one-half hour with from 200 to 400 

 cc. (depending on the nature of the material) of a mixture of alcohol and 

 hydrochloric acid (100 parts 95 per cent alcohol and 20 parts hydrochloric acid, 

 specific gravity 1.09). The mixture is then filtered and washed with warm 

 alcohol, the residue repeatedly extracted with from 300 to 400 cc. of warm 

 water, the extracts evaporated to about 40 cc. on the water bath, and, on cooling, 

 the pectin precipitated with a mixture of 300 cc. of 95 per cent alcohol and 60 cc. 

 of hydrochloric acid, specific gravity 1.09. After several hours the precipitate 

 is filtered through an ashless paper, dried at 105° C, and weighed. The ma- 

 terial is then ashed, again weighed, and the difference calculated as pectin. 



A study of the sirup precipitate in white sugar manufacture, C. E. Coates 

 and L. C. Slater (Jour. Indus, and Engin. Chem., 8 (1916), No. 9, pp. 789- 

 792). — The authors have examined the sirup precipitate obtained from two 

 factories, in one of which phosphoric acid was used in the clarification and the 

 other in which no acid was used. 



iZtschr. Analyt. Chem., 36 (1897), No. 3, p. 195. 

 •Arch. Chem. u. Mikros., 7 (1914), No. 6, pp. 285-299. 



