710 EXPEKIMENT STATIOiS' EECOKD. 



portion [was] used for the preparation of monomagnesium caseiuate by in- 

 complete precipitation with HCl. The preparation contained 0.13 per cent Mg 

 (0.22 MgO), which is the theoretical composition; or 1 gm. of casein combined 

 with 1.1X10-* gm. equivalents of Mg. This compound [was] insoluble in water 

 but soluble in 5 per cent solution of NaCl ; at 65° C. it tended to form strings 

 when drawn out. 



" To the second portion of the solution mentioned in the preceding paragraph 

 acid-free alcohol [was] added and a precipitate obtained which contained 0.24 

 per cent Mg (0.4 MgO), the theoretical composition of di-magnesium caseinate 

 being 0.26 per cent Mg (0.44 MgO) ; or 1 gm. of casein combined with 2.1X10-* 

 gm. equivalent of Mg (theoretical 2.25 XIO-*). The compound is quite easily 

 soluble in water and in a 5 per cent solution of NaCl ; at 65° it is slightly 

 sticky. 



" These four magnesium caseinates correspond to the four calcium caseinates 

 which have been previously prepared, representing octo-, penta-, di-, and mono- 

 caseinates of magne.sium." 



Why sodium citrate prevents curdling of milk by rennin, A. W. Boswoeth 

 and L. L. Van Slyke (New York ^tate Sta. Tech. Bui. 34 (1914), pp. 3-9; Amer. 

 Jour. Diseases Children, 7 {1914), No. 4, PP- 298-304). — The practice of adding 

 sodium citrate to cow's milk in the process of modifying it for infant feeding 

 purposes has been common for many years. Its use is especially valuable for 

 those children where cow's milk forms exceedingly large lumps of tough curd 

 after entering the stomach. These lumps of curd can pass practically un- 

 changed through the entire course of the intestinal canal and do, by either 

 mechanical or other means, cause serious interference with the process of 

 digestion. The favorable results attending the use of sodium citrate in pre- 

 venting the formation of these curds, however, have never been explained on the 

 basis of actual investigation. 



It is pointed out as a result of these studies that the addition of sodium 

 citrate to normal milk renders some of the insoluble calcium present soluble. 

 This increase in soluble calcium is due to a reaction between calcium caseinate 

 and sodium citrate by which is formed sodium caseinate (or calcium-sodium 

 caseinate) and calcium citrate. This reaction is also reA'ersible. 



" The curdling of milk by rennin is delayed by the pre.sence of sodium citrate; 

 when there is added 0.4 gm. of sodium citrate per 100 cc. of milk (equal to 1.7 

 gm. per ounce), no curdling takes place. The curd produced by rennin in the 

 presence of small amounts of sodium citrate (0.05 to 0.35 gm. per 100 cc. or 0.2 

 to 1.5 gi'ains per ounce) increases in softness of consistency as the amount of 

 sodium citrate in the milk increases. 



" The results of our work indicate that at the point at which rennin fails to 

 curdle milk we have in place of the calcium caseinate of normal milk a double 

 salt, calcium-sodium caseinate; this double salt, when rennin is added, is 

 changed to a calcium-sodium paracaseinate which, owing to the presence of the 

 .sodium, is not curdled. The practice of adding sodium citrate to milk at the 

 rate of 1 to 2 grains of citrate per ounce of milk appears to have a satisfactory 

 chemical basis in the reaction between the sodium citrate and the calcium 

 caseinate of the milk. The amount added is governed by the object in view, 

 viz, whether it is desired to prevent curdling or only modify the character of 

 the curd in respect to softness." 



See also a previous note (E. S. R.. 29, p. 805). 



Studies on enzym action. — VIII, A continuation of the study of the action 

 of amino acids and castor bean lipase on esters, M. L. Hamlin (Jour. Amer. 

 Cheni. Soc., 35 {1913), No. 12, pp. 1S97-1904). —Coutinmng work previously 



