New YorK AGRICULTURAL EXPERIMENT STATION. 285 
results indicate that the salts even quite alkaline to phenolphthalein 
hydrolyze to a marked degree. 
The behavior of casein salts of the alkaline earth metals has 
also been studied by W. A. Osborne! with the conclusion that they 
hydrolyze. 
A further reason for placing casein, as regards its acid properties, 
in a class with phosphoric acid, is the similar behavior of the two 
towards various indicators. Phosphoric acid like casein gives dif- 
ferent results when titrated against alkali with different indicators. 
For example, 10 cc. of a given solution of phosphoric acid was 
neutralized to methyl orange by 6.15 cc. N-1o KOH, while to give 
a perceptible pink with phenolphthalein 11.20 cc. were required. 
Viewed from the standpoint indicated by our results, casein acts 
as a very weak acid. When a sufficient excess of casein is present 
in solution (presumably as acid casein salts, possibly as free casein 
dissolved in sodium caseinate solution) the amount of hydrolytically 
freed alkali is reduced to practically zero, and the solution reacts 
neutral to the delicate indicator phenolphthalein, at the same time 
showing a minimum conductivity. Due to the weakness of its acid 
properties, a considerably greater excess of casein is required to 
render the solution acid enough to redden litmus, and still greater 
excess to neutralize to methyl orange. 
These results are presented as preliminary to a more thorough 
investigation of the problem. 
The data for plotting the HsPOs; and H.SO, curves are taken from 
Kohlrausch.2? The data for succinic acid were obtained by adding to a 
, N ‘ rex: , 
solution of 20 cc. carbonate-free = KOH in a conductivity cell successive 
portions of recrystallized succinic acid dried at 115°. The acid was weighed 
out in a small tube and portions shaken into the solution, the tube being 
weighed after shaking out each portion. By this method cumulative error 
in weighing was avoided. As one equivalent of succinic acid weighed but 
116 milligrams, the volume change caused by the addition was negligible. 
The following data were obtained. Temperature = 25°. 
* Jour. Physiol., 27:398. 1901. 
*Leitvermégen der Elektrolyte. 
