AGRICULTUEAL CHEMISTRY AGBOTECHNY. 13 



Methods of analysis used in the laboratories of the Armour Institute of 

 Technology. — Mineral analysis of water (Chem. Engin., 17 {19 IS), No. S, pp. 

 117, 118). — The methods described are for total solids, silica, iron and aluminum, 

 calcium, magnesium, sulphuric acid, alkalis, carbonates, chlorids, and free 

 carbon dioxid. The methods of calculating the results are also given. 



Food control by police oflacials, W. Bremee (Die Nahrungsmittelhontrolle 

 durch den Polizeihemiiten. Berlin, 1910, pp. IV+78). — This is a description of 

 methods of sampling for food inspection purposes. The substances which are 

 prohibited are described in detail. 



A rapid method for determining' fat in cacao with the Zeiss refractometer, 

 O. RiCHTER {Ztsclir. Untersuch. Nahr. u. Genussmtl., 24 {1912), No. 5, pp. 312- 

 319). — The methods for determining fat in milk are not applicable to the deter- 

 mination of this constituent in cacao, but the use of the refractometer for this 

 purpose suggested itself. The method which apparently gave good results em- 

 bodied extraction of the material with ether-alcohol-trisodium phosphate solu- 

 tion, determining the refraction of the fat, and calculating the amount of fat 

 present from the results by tables which are included. 



Chang-es in the methods for determining succinic and malic acids in wine, 

 C. VON DER Heide and E. Schwenk {Ztschr. Analyt. Chem., 51 {1912), No. 10- 

 11, pp. 628-638). — A modification of the methods originally suggested by von 

 der Heide and Steiner (E. S. R., 21, pp. 304, 305). 



Studies in regard to the dry substance (total solids) of milk, A. Splitt- 

 gerber {Ztschr. Untersuch. Nahr. u. Genussmtl., 24 {1912), No. 8, pp. 439-507).— 

 A study was made for the purpose of determining to what degree the milk con- 

 stituents suffer decomposition when dried for a long time. 



The changes produced in the dry substance were, in most instances, primarily 

 due to the presence of lactic acid. This acid, when heated at the usual drying 

 temperatures, will volatilize almost completely, but when present with either 

 casein, albumin, protein, lactose, or in milk itself, it becomes bound or fixed to 

 these constituents. The remainder of the acid present is decomposed, this being 

 entirely dependent upon the amount present and the time of drying. 



A loss in weight for normal milk, due to the presence of lactic acid, is usually 

 not noted during the first hour of drying, but after 2 hours it is appreciable. 

 Casein, a mixture of milk sugar and phosphates, and casein with milk and 

 phosphates after drying over 1 hour showed a marked loss in weight. Accord- 

 ing to these findings the figures obtained by the usual drying methods do not 

 represent the sum of the total solids of milk, but those given after 1 hour of 

 drying are probably correct. 



This behavior of lactic acid probably explains the fact that in the determi- 

 nation of the solids in sour milk the figures obtained do not correspond with 

 those given by the calculation methods. 



The conservation of samples of milk destined for analysis, X. Rocques 

 {Ann. Chim. Analyt., 17 {1912), No. 11. pp. 413-418).— One gm. of bichromate 

 of potash per liter is generally used in France for preserving milk intended for 

 analysis, but if the bichromate is added to milk in which decomposition has 

 already set in disintegration proceeds more rapidly. Thinking that it was the 

 lactic acid which destroyed the preserving power of the bichromate, the author 

 made some tests with solutions of these substances. He found that lactic acid 

 reduced bichromate. The bichromate had no effect upon lactose, but lactose 

 seemed to accelerate the decomposition of the bichromate. 



The conclusion Is reached that bichromate of potash is an excellent preserva- 

 tive for samples of fresh milk, but that when the sample is in a state of decom- 

 position it is necessary to examine it as quickly as possible. 



