2606 REPORT OF THE CHEMIST OF THE 
IS THE ACID-CASEIN SOLID A HYDROLIZIBLE SALT? 
In case the insoluble acid-casein were a hydrolyzible salt of an 
acid, as hydrochloric acid, casein acting as a weak base, we should 
observe the same qualitative characteristics as those noted, viz., the 
dependence of the amount of acid taken up by casein upon the 
concentration used and upon the temperature, and a loss of acid 
when the insoluble acid-casein is shaken with pure water. We 
should, however, expect somewhat more hydrochloric than sulphuric 
acid, reckoned in equivalents, to be taken from solution of equal 
concentrations, since hydrochloric acid is somewhat the stronger 
acid. Instead, the amount of sulphuric acid taken up is much the 
greater. Furthermore, according to the law of mass action and the 
behavior of chemical reactions of this class, equilibrium would 
always be reached when the concentration of the free acid had been 
reduced to a certain constant value, the amount of acid held by 
casein being no factor in the equilibrium so long as all the basic 
valences of the latter were not neutralized. According to the law 
of mass action, if we regard the insoluble acid-casein as a salt of 
an acid, say hydrochloric acid for example, hydrolyzing in accord- 
ance with the hypothetical equation, 
Casein Cly + y H,O <. Casein (OH)y+ y HCl, 
(acid-casein ) (free casein) 
equilibrium must be reached when 
Chic hocaaern (OH) y Yes 
y e te 
Ob ee ee Gl kv. 
in. which ies, = concentration of HCl; C.._... (OH) y = concen- 
tration of free casein, €tc.)y==basic valence oOfscacem. K, ye 
constant dependent on temperature. The hydrochloric acid is the 

only reagent of variable concentration. Consequently 1 the equation 
simplifies to OI 1 
The accuracy of this form of equation for reactions involving 
only one substance of variable concentration has been repeatedly 
proved by well-known reactions. In the decomposition of CaCO, 
by heat, Cio. —K,. In the reaction by which ammonia and 
*“Only gaseous and dissolved substances have varying concentrations.” 
(Ostwald Principles of Inorganic Chemistry. Translation by Findlay, p. 327, 
1902. ) 
