New York AGRICULTURAL EXPERIMENT STATION. IAT 
45° C. The coagulum is insoluble in warm 5 per ct. salt solution. 
If any soluble calcium salts present are removed by treatment 
with ammonium oxalate, the basic calcium casein is not coagulated 
on warming. Neutral calcium casein, prepared by dissolving free 
casein in limewater and making neutral to litmus, is coagulated 
on warming by soluble calcium salts. The coagulum is insoluble 
in dilute salt solution. The neutral calcium casein existing in 
milk is coagulated on warming by a few drops of a solution of 
calcium chloride. If we add to milk an amount of acid insuffi- 
cient to cause coagulation or to remove from its combination the 
calcium of the calcium casein, we can produce some coagulation 
on warming. This is probably due to the conversion of insoluble 
into soluble calcium salts, and the same result follows as when 
we add a soluble calcium salt directly to the milk. 
The coagulation of calcium casein compounds by a soluble cal- 
cium salt may be due to purely physical change in the calcium 
casein compounds, or there may be a loose chemical combination 
between the soluble calcium salt and the calcium casein com- 
pounds, the resulting compound being insoluble in the neutral or 
slightly acid medium. 
THE RELATION OF THE SALT-SOLUBLE COMPOUND OF CASEIN TO MILK- 
CASHIN. 
The preparations of calcium casein, while slightly soluble in 
hot 50 per ct. alcohol, were insoluble in warm 5 per ct. salt 
solution. None of these preparations showed in any marked 
degree the properties of the compounds that we have called casein 
mono-salts. We have already called attention to the fact that, 
in making an ash-free preparation of casein from cows’ milk we 
found it to be readily soluble in both warm dilute salt solution 
and in 50 per ct. hot alcohol. This suggested that there might 
be a close relation between these compounds, and we therefore 
made several preparations, the details of which we now give. 
Preparation 1, by use of hydrochloric acid.—We diluted 2 
liters of skimmed milk with 5 volumes of distilled water and 
warmed the mixture to 45° GC. Dilute hydrochloric acid was 
added, accompanied by vigorous stirring to keep the precipitate 
in a finely divided condition. After the precipitate had settled, 
the supernatant liquid was poured off, the precipitate was tritu- 
