Abstract
LONDON. Society of Public Analysts, Mar. 6.—Christine Mary Fear: On the alkaloid test for tannin. It has frequently been asserted that most alkaloids are precipitated by tannin, but the author's experiments show that the only alkaloids giving appreciable precipitates with tannin solutions alone are brucine, caffeine, cinchonine, cinchonidine, quinine, and strychnine.—A. L. Andrews: The cryoscopic method for the detection of added water in milk. The determination of the freezing-point affords a simple and trustworthy means of detecting added water in milk. Genuine milk has a freezing-point not higher than -0–550° C., when determined by the method in use in the New Zealand Dominion Laboratory. If the freezing-point rises to -0–530° C., watering may be suspected, and if to -0–520° C., the milk has certainly been adulterated with 5 per cent of added water.—A. J. Parker and L. S. Spackman: Investigations on the relations between the acidity and freezing-point of milk. The normal acidity of fresh milk is 0-14 per cent. The correction factor is 0-003° C. for each 0-01 per cent excess acidity between acidities of 0-17 and 0-60 per cent, and 0-010° C. for acidities ranging from 0-14 to 0-17 per cent lactic acid. When the cryoscopic method. is used for the determination of added water in milk, it can be applied with accuracy only when the samples are quite fresh.
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