CHEMISTRY. ^7l 



quantitatively tlie extraction witli etlier nmst be followed by at least 

 30 extractions with etliyl alcohol or -0 with nietliyl alcohol, each 

 extraction lastino- 8 to 10 minutes, but never longer than 15 minutes. 



The determination of fat in milk by centrifugal means, and a 

 comparison of the Babcock and Gerber methods, J. Zehenter 

 [Pro<ira)ni)i Obcrrcal.schnir in Innnhnivk far lSU3-'Ji; ahs. in Cliem. 

 Centbl, 1894, II, Xo. .9, j^- 458; and in Ghem. Ztg., 18 {1894), No. 66, 

 Repert., p. 198). — A historical review is giveu ot the development of 

 centrifugal methods for determining; fat m milk, description of various 

 centrifuiial methods, and a comparison of the Babcock and Gerber 

 methods with the gravimetric and Soxhlet's aerometric methods. In 

 Gerber\s "acid biitj^rometric" method' the milk is mixed with a quan- 

 tity of amyl alcohol in a long-necked graduated tube, an acid mixture 

 not described is added, and the tube is whirled in a warm centrifuge. 



In this comparison 3 out of 34 tests with tlje Babcock method dif- 

 fered from the graviinetric results by more than 0.1 per cent, 6 by more 

 than 0.05 per cent, and the rest by less than 0.005 per cent; hence 73.5 

 per cent of the determinations was within 0.05 per cent. With Ger- 

 ber's method 63 per cent of the results agreed within 0.05 per cent with 

 the gravimetric results, and the largest variation with whole milk was 

 0.11 per cent. 



The author linds little to choose between the two methods in accu- 

 racy or rapidity. At present the Babcock machine for an equal num- 

 ber of tubes is said to cost more thau the Gerber, although the single 

 determinations with the latter cost nearly twice as much as with the 

 former, owing to tlie expensiveness of Gerber's acid mixture. It is 

 said, however, that Gerber proposes to substitute sulphuric acid of 

 1.82 to 1.825 sp. gr. for his acid mixture and use larger tubes, which will 

 reduce the cost of making the test. 



The recognition of vegetable oils in butter, Schonvogel (67<em. 

 Zffj., 18 (1894), Xo. 75,' p. 1449). — In examining artificial butter in the 

 Caucasus, said to be made from a mixture of animal and vegetable fats, 

 the author has found tlie reactions with concentrated borax solution 

 useful in distinguishing vegetable oils, and caustic soda solution for 

 distinguishing butter from pure margarin. 



The determination of volatile and insoluble fatty acids in 

 butter fat, W. H. Beal {Jour. Amer. Chem. A'oc, 16 {1894), Xo. 10, 

 ■pp. 673-676). — For determining the volatile acids approximately 2.5 

 gm. of the pure fiit is saponified with 2 cc. of a solution prepared by 

 dissolving 50 gm. of potassium hydroxid (free from carbonates) in 100 

 cc. of water and 5 cc. of strong (05 i)er cent) alcohol, heating with a reflex 

 condenser on a water or steam bath, and removing the last traces of 

 alcohol by means of a filter pump. 



"Tlie soap thus obtained is flissolved in 30 cc. of warm water and decomposed 

 with 20 cc. of a 20 per cent solution of orthophosphorie acid. The volatile acids are 



' Chem. Ztg., 16 (1894), pp. 1839, 1840; Chem. Centbl., 1893, i, p. 233, and ii, p! 665. 



