New York Agricultural Experiment Station. 317 



In the second experiment, further evidence is furnished, showing 

 that neutral calcium phosphate (CaHP0 4 ) is a normal constituent 

 of milk. Four 500-c.c. bottles were filled with separator skim-milk 

 to which some formaldehyde had been added, and, after standing 

 at room temperature for 4 days, were whirled in a Bausch and 

 Lomb precision centrifugal machine for 30 minutes at a speed of 

 1,200 revolutions per minute. A sediment was deposited, which 

 after purification by treatment with alcohol and ether, as previously 

 described, weighed 0.4 gram. Analysis of this gave the following 

 results: Casein, 20.78 per ct.; total phosphorus, 18.38 per ct.; phos- 

 phorus combined with casein, 0.15 per ct.; phosphorus combined as 

 phosphates, 18.23 per ct.; calcium, 22.79 per ct.; ratio of organic 

 phosphorus to inorganic phosphorus, 1:121; casein as gram equiva- 

 lents of acid, 18.7 x 10 -3 ; phosphates as gram equivalents of di-basic 

 acid, 1175. x 10~ 3 ; sum of casein and phosphates as gram equiva- 

 lents of acid, 1194. x 10~ 3 ; gram equivalents of calcium, 1140.x 

 10" 3 . 



In these figures, we again find the same balance between bases 

 and acids, which can mean only that the phosphate compound 

 deposited is di-calcium phosphate (CaHP0 4 ). The degree of centri- 

 fugal force developed was sufficient to throw out a relatively large 

 amount of di-calcium phosphate but not powerful enough to throw 

 out very much casein, thus serving as a means of effecting a nearly 

 complete separation of these two constituents. 



Babcock 5 whirled skim-milk in a separator for several hour^, 

 removing portions from time to time for analysis and finally deter- 

 mining the amounts of casein, calcium and phosphorus in the 

 deposited " slime." While the experiments were preliminary in 

 character and the results not sufficient to base permanent conclusions 

 on, they tended to show that the casein and phosphates were not in 

 combination. From the analytical results showing the relation of cal- 

 cium to phosphorus, the conclusion was drawn that tri-calcium phos- 

 phate is the compound present in milk. The figures for calcium and 

 phosphorus were based upon the total amounts contained in the 

 deposit and no allowance was made for the calcium in combination 

 with casein and the phosphorus of the casein. This fact accounts 

 for the difference between the results presented by him and the 

 conclusions reached by us. A recalculation of his data, after 

 deducting the amounts of calcium and phosphorus combined with 

 casein, gives figures that correspond to the composition of CaHP04 

 and not Ca 3 P20s, thus confirming the results of our work. 



ACIDITY OF MILK AND MILK-SERUM. 



Both fresh milk and the serum from fresh milk show a slight 

 acid reaction to phenolphthalein. This has been believed to be due 



«Wis. Agrl. Expt. Sta. 12th An. Rept., p. 93. 



