396 Chittenden and Painter— Casein and its 
protocaseose was concentrated, precipitated with alcohol, the precipi- 
tate dissolved in water, again precipitated with salt in substance, the 
precipitate dialyzed, this time without showing any heterocaseose, 
and finally precipitated with alcohol, washed with alcohol and ether 
and dried at 105° C. in vacuo (Protocaseose D 1). The product was 
analyzed with the results shown in the preceding table. 
On adding more sodium chloride to the first filtrate from the above 
precipitate, thereby completely saturating the solution, a second 
precipitate of protocaseose was obtained, which was purified in the 
same manner as the preceding preparation. The only difference 
noticed while purifying the substance was that, on dialysis, nothing 
corresponding to heterocaseose separated from the fluid. After final 
washing with alcohol and ether, the substance was analyzed with the 
results shown in the accompanying table (Protocaseose D 2). 
The difference in the results will be discussed later on. 
The original salt-saturated filtrate was precipitated with a little 
acetic acid, and the protocaseose so precipitated dissolved in dilute 
sodium carbonate. The solution was then neutralized and dialyzed 
in running water until all chlorine was removed. The substance was 
then separated by precipitation with alcohol, and ultimately purified 
as described previously (Protocaseose D 3). The addition of a little 
more acetic acid to the acetic acid and salt-saturated filtrate from the 
above, gave a still further precipitate of caseose ; presumably proto- 
caseose with perhaps a trace of deuterocaseose, which was filtered 
off, washed with saturated salt solution and then freed from acid and 
purified in the same manner as the preceding preparation (Proto- 
caseose D 4). 
The two last products, after being dried at 105° C. in vacuo, were 
analyzed with the results shown in the following tables. 
Comparing these two tables, it is seen that the difference in per- 
centage composition of the two ash-free substances is not very great, 
and taking into consideration the large percentage of ash, it is proba- 
ble that the two latter precipitates have approximately the same 
composition. 
D. Deuterocaseose. 
The filtrate, from which certainly all protocaseose had been re- 
moved by acetic acid, and in fact nearly everything precipitable by 
acid from the salt-saturated fluid, was treated with ammonium 
sulphate in substance. A gummy precipitate resulted, which natu- 
rally enclosed considerable salt, and which for purification was dis- 
