390 Chittenden and Painter— Casein and its 
with alcohol and the substance finally dried at 105° C. in vacuo 
(Protocaseose B 1). Its composition is shown in the accompanying 
table. 
Such portion of the protocaseose as was not precipitated the 
second time by salt alone, was precipitated by a little acetic acid. 
At first, the precipitated substance was insoluble in water (no reac- 
tion with acetic acid and potassium ferrocyanide), but after being 
washed with salt solution until the acid reaction had nearly disap- 
. peared, it then dissolved quite appreciably in water, as evidenced by 
the reaction with acetic acid and potassium ferrocyanide. The bulk 
of the precipitate, after being washed, was dissolved in a little very 
dilute sodium carbonate, the solution made exactly neutral with 
hydrochloric acid and then dialyzed until all chlorine was removed 
from the solution. The caseose, after concentration of the solution, 
was precipitated by alcohol, washed with alcohol and ether and 
finally dried at 105° C. im vacuo. The composition of the substance 
(Protocaseose B 2) is shown in the accompanying table. 
B. Deuterocaseose. 
Deuterocaseose was separated from the filtrate from the first 
sodium chloride precipitate, in the same manner as in the preceding 
digestion. Like A. deuterocaseose, this precipitate was at first in- 
soluble in salt solution and in water, but after being washed for 
some time with saturated salt solution, it was found to be gradually 
dissolved, as shown by the rapid disappearance of the precipitate 
and the pronounced reaction with acetic acid and potassium ferrocy- 
anide in the wash-fluid. - Evidently the acid is easily removed from 
the compound by simple washing and when that has been effected, 
the substance becomes soluble, or else the acid compound is more 
insoluble in water containing a little free acid, than in water or 
salt solution alone. Hydrochloric acid and acetic acid seem to 
act alike. The substance is readily soluble in dilute sodium car- 
bonate and is not precipitated by neutralization, but is quickly 
thrown down by a slight excess of hydrochloric or acetic acid. This 
compound was not analyzed, but was used in studying the reactions 
to be described later. 
Digestion C. 
In both of the preceding digestions, the products formed resulted 
from the action of an exceedingly vigorous pepsin mixture. In the 
