New YorK AGRICULTURAL EXPERIMENT STATION. 183 
acid, or 1 gram of casein would require for complete saturation 
15.6 ce. of 7, hydrochloric acid. The work, repeated on 5 cc. 
of milk containing .031 gram of nitrogen, gave 15.9 cc. of ;', 
hydrochloric acid as the amount required to saturate 1 gram 
of casein. 
In the manner in which this work was done, it is recognized 
that we were dealing not with casein alone, but with the two 
principal proteids of milk, casein and albumin. However, there 
is no reason to believe that the results would be essentially 
different with pure casein. We shall later secure results with 
casein alone. 
(3) Deternination of amount of 74 hydrochloric acid required 
to saturate the unsaturated salt of paracasein.— To 50 cc. of the 
salt-extract of some curd, containing .058 gram of nitrogen in 
the form of the unsaturated hydrochloric acid salt of para- 
casein, we added 10 ce. of 4 hydrochloric acid for the purpose 
of converting the unsaturated into the saturated salt. We 
then added 5 cc. of neutral calcium picrate to facilitate clear 
filtration. The mixture was filtered, the precipitate washed, 
and the filtrate treated with ;, sodium hydroxide, rosolic acid 
being used as indicator. Neutralization required 7.1 cc. of 75 
sodium hydroxide. Hence, to saturate the salt-soluble com- 
pound, equivalent to .058 gram of nitrogen, required 2.9 cc. ;'; 
hydrochloric acid. Using 6.39 as the nitrogen factor of para- 
casein, it required 7.83 cc. of ;4 hydrochloric acid to convert 
1 gram of the unsaturated into the saturated hydrochloric acid 
salt of paracasein. 
We saw above that it required from 15.6 to 15.9 ce. 74, hydro- 
chloric acid to saturate milk-casein completely, or, more strictly, 
casein mixed with a small amount of milk-albumin. Now, the 
amount of 55, hydrochloric acid required to convert the unsaturated 
into the saturated hydrochloric acid salt of paracasein, 7.83 cc., is 
just one-half of 15.7 cc., the amount of ;*; hydrochloric acid 
required to form a saturated compound. Hence, the amount of 
combined acid in the saturated salt is twice that in the unsatu- 
rated salt; in other words, the unsaturated salt appears to be 
a mono-acid salt, and the saturated a di-acid salt. These results, 
