New York AGRICULTURAL EXPERIMENT STATION, 185 
was used, bringing the total up .20 gram of lactic acid, there 
was a large increase of the salt-soluble compound, and this was 
still greatly increased by additions of lactic acid above .20 gram 
up to .50 gram. It is possible that there may be formed with 
acids a paracasein salt containing still less acid than the half- 
saturated salt, or, it may be that the acid which disappears 
unites with some of the insoluble inorganic salts in the curd. 
SOLUBILITINS OF THE SALTS FORMED BY CASEIN AND PARACASEIN WITH 
ACIDS. 
(1) Saturated salts—-The saturated acetic and lactic acid 
salts of casein and paracasein, as well as the hydrochloric and 
sulphuric acid salts, are practically insoluble in all the media 
tried. They are insoluble in water; in 5 and 10 per ct. solutions 
of sodium chloride; slightly soluble in 50 per ct. boiling alcohol, 
practically insoluble at 122° F. (50° C.) in saturated solution of 
calcium carbonate, and in 2 per ct. solution of calcium lactate at 
122° F. (50° C.). They dissolve; of course, in excess of acid or 
dilute alkali. 
(2) Unsaturated salts——The unsaturated or half-saturated 
salt of each of the acids mentioned above is insoluble in water; 
completely soluble in 5 per ct. solutions of sodium chloride at 
180° to 140° F. (55° to 60° C.), not separating again on cooling, 
but entirely separating by dialysis in water; soluble in 59 per ct. 
boiling alcohol, but separating again on cooling; only slightly 
soluble in saturated solution of calcium carbonate at 122° F. 
(50° C.), or in 2 per ct. solution of calcium lactate. 
(3) Haplanation of Danilewsky’s error.—Danilewsky’s” early 
supposition, that casein consists of two proteid bodies separable 
by hot 50 per ct. alcohol, finds a reasonable explanation in the 
fact that the unsaturated salt formed by casein with an acid is 
soluble in 50 per ct. hot alcohol, while the saturated salt is insol- 
uble in this medium. When the usual method is employed of 
precipitating casein from milk by means of dilute acid, the 
resulting product can easily be a mixture of the unsaturated 
and saturated salts, the quantity of each present depending 
12Zeit. f. Physiol. Chem., 7: 227 (1883). 
