238 REPORT OF THE CHEMIST OF THE 
treatment with rennet is coagulated at ordinary temperatures by 
soluble calcium salts. Soluble calcium salts, as calcium chloride, 
coagulate both neutral and basic calcium casein on warming to 
35° to 45° C. 
6. Casein Present in Milk as Neutral Calcium Casein.—In its 
behavior toward soluble lime salts on warming and at ordinary 
temperatures after treatment with rennet, neutral calcium casein 
behaves like milk-casein, and casein is probably present in 
cows’ milk as the neutral calcium casein. 
7. Identity of Base-Free Casein and the Salt-Soluble Proteid. 
—-A base-free casein, prepared either directly from milk or by 
treating a lime-water solution of free casein with an acid to the 
point of acidity with litmus, is readily soluble in warm 5 per ct. 
salt solution and in hot 50 per ct. alcohol. This body, when 
freshly prepared and sufficiently warmed is very plastic and 
ductile. It behaves in all respects like the compound which we 
were formerly led to regard as a compound formed by combina- 
tion of casein and an acid and which we regarded as a casein 
mono-salt of the acid precipitant. 
8. Relation between Two Series of Compounds previously 
called Casein Mono-Salts and Casein Di-Salts of Acids.—When 
one gram of base-free casein is treated with about .5 cc. of =. 
hydrochloric acid, a substance is formed which is insoluble in 
warm 5 per ct. salt solution and in hot 50 per ct. alcohol and 
which is no longer plastic or ductile on warming. This is like 
the substance usually formed when milk coagulates by natural 
souring. By treating base-free casein with dilute acid, it was 
found that one gram of base-free casein appears to combine with 
about .5 ce. of 2. hydrochloric acid, forming a casein salt of 
hydrochloric acid. While the compounds formerly regarded by 
uS as casein mono-salts of acids have been shown by us to be 
identical with base-free casein, the compounds which we called 
casein di-salts of acids are compounds. formed by combination 
of acids with free casein. 
9. Paracasein and Its Compounds.—A preparation of base- 
free paracasein was made, and from this dissolved in lime-water 
were prepared (1) basic calcium paracasein, containing in com- 
bination about 2.40 per ct. of calcium oxide, and (2). neutral 
calcium paracasein containing about 1.50 per ct. of Cont 
calcium oxide. 
