008 EXPEKIMENT STATION RECORD. 



nitrogen, ])hospborus, and calcium. Rennin action produces no solulile nitrogen 

 or phosphorus. Trypsin splits off both soluble nitrogen and phosphorus, while 

 the Withnnia enzym also produces soluble nitrogen and phosphorus but in 

 smaller absolute quantities. The cleavage products are specific for each enzym 

 and it is to this difference of enzym action that the variation in behavior of the 

 resulting casein is to be ascribed. The precipitation of calcium caseinate by 

 soluble calcium salts is not due to any chemical combination with these. The 

 caseinogen once exposed to enzym action and redispersed can not be rendered 

 more precipitable by renewed enzym action. If the enzym be sufficiently con- 

 centrated, precipitates are obtained without the addition of calcium salts and 

 tlie same tiling occurs with more dilute enzym solutions when the temperature 

 is raised above 45°." 



The importance of using an appropriate method for preparing casein is 

 pointed out. " In preparations for milk the use of sodium hydrate was avoided 

 so as to escape the possibility of hydrolyzing the protein. Van Slyke and 

 Bosworth have used ammonia in the final stages of their method [E. S. R., 29, 

 p. 9], allowing it to remain in contact with the caseinogen overnight. Their 

 preparations have a very low ash content and the phosphorus content is the 

 lowest yet recorded. This is due possibly to removal of phosphorus by the 

 action of the alkali." 



Caseinogen and casein, A. Geake {BiocJicm. Jour., S {lOlJ/), i\'o. 1, pp. 30- 

 37).— The object of this investigation was to determine the difference, if any, 

 between caseinogen (casein) and casein (paracasein) in elementary comiwsi- 

 tion and in the Hausmann numbers.* See also a note by Osborne and Harris 

 (E. S. R., 15, p. 221). 



A slight modification of the Carius method was used for the sulphur deter- 

 mination. The results obtained for sulphur were higher than those which have 

 been previously obtained for caseinogen. "The sulphur contents of caseinogen 

 and casein appear to be identical, but casein apparently contains more phos- 

 phorus than caseinogen. The ditlerence is, however, not sufficient to warrant 

 the supposition that the two proteins are chemically different." 



The figures for the Ilausmauu numbers vrere also too low to establish any 

 definite differences. 



The detection of potassium with tartaric acid, L. W. Winkler (Ztschr. 

 Angew. Chem., 26 {1913), No. 29, Aufsatzteil, p. 20S).— Potassium bitartrate has 

 the property of forming hypersaturated solutions, so that the use of a solution 

 of tartaric acid as a reagent for detecting potassium often fails. If. however, 

 the tartaric acid is used in powdered form and the solution is not too dilute, 

 the characteristic precipitate is quickly obtained. The procedure recommended 

 is as follows : 



To 10 cc. of an approximately 5 per cent neutral solution of the substance un- 

 der examination is added 0.5 gm. of crystalline powdered acetate, then approxi- 

 mately 0.5 gm. of pov>'dered tai'taric acid, and the mixture is shaken thoroughly. 

 If no potassium (or ammonium, rubidium, or c.-iesium) is present the solution re- 

 mains perfectly clear. If the solution contains 0.2 per cent or more of the potas- 

 sium ion the reaction occurs only after one to two minutes. It is advisable to 

 conduct a control test with a solution of sodium chlorid or distilled water. The 

 reaction can be employed for potassium chlorid. bromid. iodid, nitrate, chlorate, 

 sulphate, etc., and the organic compounds of potassium, with the exception of 

 tartar emetic. With alum the reaction is less sensitive. 



» Hoppe-Scyler's Ztschr. rhyslol. Chem., 27 (1899), No. 1-2, pp. 95-108; 29 (1900), 

 No. 2, pp. 136-145. 



