AGRlfeULTUBAL CHEMISl^Y AGBOTECHNY. 11 



monobasic and dibasic, one set containing twice as mucli base as tlie other. 

 In the dibasic compounds, 1 gm. of casein requires between 2.2X10—* and 

 2.3X10 — ■* gm. equivalents of hydroxid to form a compound soluble in water but 

 easily precipitable by even a small amount of a soluble chlorid of calcium, 

 strontium, or barium. In the dibasic compounds, 1 gm. of casein combines 

 (a) with 0.44 to 0.46 gm. Ca, (b) with 0.96 to 1.01 gm. Sr, and (c) with 1.51 

 to 1.58 gm. Ba. In the monobasic salts, 1 gm. of casein combines with about 

 1.1X10—* gm. equivalents of hydroxids to form insoluble compounds, which are 

 soluble in 5 per cent solution of chlorid of sodium, ammonium, or potassium. 

 This solubility is due to an exchange of bases; for example, insoluble mono- 

 calcium caseinate is changed by treatment with solution of NaCl into soluble 

 monosodium caseinate and CaCa-, as shown by special experiments. 



Special preparations were made of monoammonium caseinate and of mono 

 and dicalcium caseinates, each compound being isolated and prepared in dry 

 form. >■ These were found to have essentially the composition called for by the 

 previous results obtained with the volumetric work. 



" On the basis of the composition of the basic calcium caseinate and monocal- 

 cium caseinate, the former has a valency of 8. These relations indicate the 

 molecular weight of casein to be 8888. and the equivalent weight 1111." 



For preparing paracasein, " separator skim milk is heated to 37° C. and 

 treated with 0.12 cc. of rennet-extract (Hansen's) per 1,000 cc. of milk. The 

 milk is allowed to stand until completely precipitated. The resulting curd is 

 broken up by vigorous stirring, the whey removed, and the precipitated para- 

 casein washed freely with water. It is then dissolved in dilute,NH40H, repre- 

 eipitated with acid, and the operation continued and completed as in the case 

 of casein." 



By the same methods of study, paracasein was shown to form with calcium 

 a paracaseinate similar in composition and properties to that of basic calcium 

 caseinate. In acid or unsaturated paracaseinates of ammonium, sodium, and 

 potassium, 1 gm. of paracasein combines with just double the alkali in the 

 corresponding casein compounds, and forms soluble compounds which are acid 

 to both litmus and phenolphthalein. A preparation of monoammonium para- 

 caseinate in dry form gave results agreeing faii'ly well in composition with 

 the results obtained by volumetric work. 



Mono- and dibasic paracaseinates of calcium, strontium, and barium were 

 prepared in the same manner as the corresponding caseinates, and were shown 

 to differ from them in having just twice as much of the basic element. Their 

 properties resemble those of the corresix>nding caseinates. 



" The valency and molecular weight of paracasein are shown to be one-half 

 those of casein. When casein is treated with rennet-enzym, the casein molecule 

 appears to be split into 2 molecules of paracasein. 



" During the manufacture and ripening of Cheddar and many other kinds of 

 cheese, a protein is always formed which is insoluble in water but soluble in 

 a 5 per cent solution of NaCl. Former studies led to erroneous conclusions 

 regarding its identity. Extended study shows that this substance is identical 

 with monocalcium paracaseinate." [E. S. R.. 14, p. 607; 19, p. 176; 21, p. 177.] 



The quantitative separation and determination of subsidiary dyes in the 

 permitted food colors, W. E. Mathewson (U. S. Dept. Agr., Bur. Chem. Girc. 

 lis, pp. 4). — Most simple commercial dyestuffs are often found to contain large 

 amounts of subsidiary coloring matters, and the amount of these present is of 

 some importance because they may be the most objectionable of the impurities. 

 As reasonably pure coloring matters are necessary when examining methods 

 for the estimation of subsidiary colors, some colors were prepared in the labor- 

 atory and others were obtained in commei'ce. The dyes considered, which were 



