312 Report of the Department of Chemistry of the 



(i) insoluble calcium (g minus h), (j) total magnesium, (k) soluble 

 magnesium, (1) insoluble magnesium (j minus k). The determina- 

 tions of total phosphorus, total calcium and total magnesium were 

 made with the normal or whole milk, while those of soluble phos- 

 phorus, soluble calcium and soluble magnesium were made with the 

 serum obtained by filtering through Pasteur-Chamberland filtering 

 tubes in the manner already described. The amount of organic 

 phosphorus was found 3 by multiplying the percentage of casein 

 by 0.0071. For convenience of reference, the analytical data are 

 arranged in two tables, II and III. 



The data in Table II afford a basis for ascertaining the quantita- 

 tive relation between casein and the phosphates. If casein is 

 chemically combined with phosphates in milk, there should be a 

 fairly definite and uniform relation between these constituents in 

 the insoluble portion of milk, or, stated in another way, the organic 

 phosphorus of casein should show a somewhat uniform ratio to the 

 insoluble inorganic or phosphate phosphorus. In column 10 of 

 Table II are given the results of calculations based on our data, 

 which show the amount of insoluble inorganic phosphorus for one 

 part of organic (casein) phosphorus. It is seen that the ratio varies 

 between the wide limits of 1 : 0.82 and 1 : 2.47. Even in the case of 

 milk from the same animal at different stages of lactation, the pro- 

 portional amount of inorganic phosphorus varies widely, as from 

 0.98 to 1.62 with cow No. 3, from 1.29 to 1.79 with cow No. 5, and 

 from 1.14 to 1.65 with cow No. 7. The only conclusion furnished 

 by these results is that there is no evidence of chemical combi- 

 nation between the casein and the phosphates of milk. Additional 

 evidence in confirmation of the foregoing statement will be furnished 

 later in connection with the discussion of another phase of the 

 subject. 



Another interesting point connected with insoluble phosphates 

 and casein in milk is as to the exact compound of calcium phosphate 

 and of calcium caseinate existing in the milk. Soldner's inferential 

 statement that milk-casein is neutral calcium caseinate (containing 

 about 1.07 per ct. of calcium), has been generally accepted, not so 

 much because of positive proof but because of absence of any proof 

 to the contrary. Regarding the form of the compound in which 

 phosphates exist in milk, all three forms (mono-, di-, and tri-basic 

 phosphates) have been thought to be present. The insoluble phos- 

 phates have been regarded as a mixture of di- and tri-calcium phos- 

 phates. 



Bearing on this question, we present data embodied in the follow- 

 ing tables, III and IV. 



3 Bosworth and Van Slyke. N. Y. Agrl. Expt. Sta. Tech. Bui. 37 and Jour. Biol. 

 Chem., 19:67. 



