New YorK AGRICULTURAL EXPERIMENT STATION. 205 
From the foregoing considerations, it is evident that the reaction 
between casein and dilute-acids shows the characteristics of adsorp- 
tion phenomena. 
IS THE REACTION A CASE OF SOLUTION OF ACID IN CASEIN? 
Most of the qualitative characteristics of the reaction, such as the 
lack of definite combining proportions and the ability of the acid to 
divide itself according to a definite ratio between casein and water, 
are characteristics of the partition of a solute between two solvents, 
as well as of adsorption. The behavior of the ratio - in the case 
mt 
in question particularly when sulphuric acid is considered, does not, 
however, correspond to the conditions of distribution in such cases. 
To quote Walker! in regard to the law of distribution in solution: 
“Tf the molecular weight of the substance in one solvent is n times 
as great as its molecular weight in the other solvent, then, when 
equilibrium is attained, the nth root of the concentration in the first 
solvent will bear a constant ratio to the concentration in the second 
solvent.” According to this, the molecular weight of hydrochloric 
acid would have to be regarded as the same in water that it is in 
its hypothetical solution in casein, in order that the ratio of concen- 
tration of acid in casein to concentration of acid water should be 
constant. As is shown, however, by the freezing point, osmotic 
pressure and electrical conductivity of hydrochloric acid solutions, 
the hydrochloric acid molecule is almost completely dissociated in 
water at the concentrations employed. An equal degree of dissocia- 
tion is required by the laws of solution for the hydrochloric acid in 
the casein, where it is from 100 to 150 times as concentrated as in 
the water. This would require us to regard casein as a solvent 
having a remarkable dissociating effect, far surpassing that of water, 
which is very improbable. In the case of the reaction with sul- 
phuric acid in which the ratio decreases as concentration of acid in 
water increases, the laws of solution require a much smaller molec- 
ular weight for the sulphuric acid in casein than that of sulphuric 
acid in water solution, which is clearly an impossibility. Irom the 
foregoing considerations, it is evident that the hypothesis of solution 
does not apply to the action under consideration. 
*Jour. Chem. Soc. [London], Trans., 69:1335. 1806. 
