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Primary Cleavage Products. 387 
acetic acid and potassium ferrocyanide, but later on, these reagents 
gave a heavy precipitate, showing plainly that the substance was 
dissolving. The entire precipitate was thereupon dissolved in very 
dilute sodium carbonate, the solution made exactly neutral with 
hydrochloric acid and then dialyzed. After remaining in the dial- 
yzers for nearly a week the fluid was removed, filtered from some 
heterocaseose which had separated, evaporated to a syrup on 
the water-bath and precipitated with alcohol. This precipitate 
was re-dissolved in water; the solution made exactly neutral to 
test papers and again dialyzed. From this solution, the caseose 
was finally precipitated by alcohol, after suitable concentration of 
the fiunid, washed with alcohol and ether and dried at 105° C. 
in vacuo. The final solution, prior to precipitation by alcohol, 
was perfectly neutral and quite clear, showing no evidence of the 
presence of any heterocaseose. " 
The composition of the substance is shown in the accompanying 
table. 
Digestion B. 
In this digestion, 750 grams of freshly prepared casein were mixed 
with 4 litres of 0-4 per cent. hydrochloric acid, the mixture warmed 
at 45° C., and then 800 c. c. of pure pepsin solution added. The mix- 
ture was warmed at the above temperature for one hour and a half, 
then neutralized and filtered, and the clear filtrate saturated with 
sodium chloride. This precipitate, as in the preceding digestion, 
was washed thoroughly with saturated salt solution, then succes- 
sively extracted with 10 and 5 per cent. salt solution and finally 
with water, leaving a small residue of dyscaseose soluble only in 
0-2 per cent. hydrochloric acid. The united filtrates, containing 
proto and heterocaseose, were again precipitated with salt and then 
treated as described under protocaseose B. 
B. Protocaseose. 
The protocaseose formed in this digestion and twice precipitated 
by salt, was dissolved again in water, filtered through paper and 
then dialyzed until no chlorine reaction could be obtained with 
silver nitrate. Quite a little heterocaseosé separated from the solu- 
tion during dialysis, which was removed by filtration. The fluid 
was then concentrated, the substance precipitated by alcohol, again 
dissolved in water and dialyzed. This time, as no heterocaseose 
separated from the fluid, the solution was concentrated, precipitated 
