New York Agricultural Experiment Station. 287 



INTRODUCTION. 



The practice of adding sodium citrate to milk used as infant food 

 has been common for many years. It has found application espe- 

 cially in the treatment of certain types of "feeding-cases" in which 

 untreated milk, after entering the stomach, forms abnormally large 

 chunks of tough curd, shown by Talbot 1 to consist of casein. These 

 lumps of curd may pass practically unchanged through the entire 

 intestinal canal, causing mechanical irritation, which often results 

 in serious interference with the process of normal digestion. 

 Empirical practice has shown that this abnormal curdling of milk 

 may, to some extent, be modified or controlled by the addition of 

 sodium citrate at the rate of 1 or 2 grains per ounce of milk. While 

 various suggestions have been offered to explain the results observed, 

 these have been based so little on demonstrated chemical facts as 

 to partake largely of the nature of guesswork. 



In our work 2 on the compounds of casein and paracasein we 

 obtained certain results which appeared to suggest a simple and 

 satisfactory explanation of the marked effect produced by the addi- 

 tion of sodium citrate to milk. Work has been done to test the 

 application of the suggested explanation and the results are pre- 

 sented in this paper. 



THEORETICAL CONSIDERATIONS. 



In order that the details of our investigation may be more readily 

 understood we will call attention to certain fundamental facts which 

 have been brought out in our former work before we give the details 

 of our present investigation. In the work to which reference is 

 made in the paragraph preceding, the following points maybe regarded 

 as being established as far as the data now at hand enable us to 

 reach any conclusions: 



1. Casein is a protein showing the characteristic property of an 

 acid in that it combines with metals or bases to form compounds 

 known as caseinates. 



2. The molecular weight of casein is 8888, and it can combine 

 with eight equivalents of a monovalent metal or base. For example, 

 the compound of casein containing the largest amount of a mono- 

 valent metal like sodium could be represented by the formula Nas 

 casein (sodium caseinate); the corresponding calcium compound is 

 Ca4 casein (calcium caseinate). 



1 Talbot, F. B. Boston Med. and Surg. Jour., June 11, 1905, p. 205, and Jan. l t 



1909, p. 13. 



2 Van Slyke and Bosworth. Jour. Biol. Chem., 14:206, (1913), and Technical 



Bull. No. 26, N. Y. Agricultural Experiment Station; also Bosworth: Jour. 

 Biol. Chem., 15 : 231, (1913), and Technical Bull. No. 31, N. Y. Agricultural 

 Experiment Station. 



