— 184 REPORT OF THE CHEMIST OF THE 
it is true, were obtained, in one case, with milk-casein not 
strictly pure and, in the other case, with the paracasein deriva- 
tive of milk-casein, and it may be thought that results secured 
in this way do not justify the conclusion drawn in regard to the 
existence of two such distinct combinations of an acid with 
casein and paracasein. But, aside from the data presented here, 
there is abundant evidence that both milk-casein and paracasein 
form at least two salts, corresponding to a half-saturated or 
mono-acid salt, and a saturated or di-acid salt. 
POSSIBILITY OF AN ADDITIONAL COMPOUND OF PARACASEIN WITH ACID. 
There is evidence that small amounts of acid can disappear in 
cheese-curd without a corresponding increase of salt-soluble 
compound. This fact is illustrated by the following experiment: 
We coagulated with rennet 3 liters of freshly drawn milk, to 
which ether had been promptly added, and then warmed the 
milk to 107° F. (42° C.) in order to shrink and harden the curd. 
Portions of 25 grams each of this curd were ground with sand, 
placed in Erlenmeyer flasks, covered with 100 ce. of water, 
heated for 10 minutes at 185° F. (85° C.) to check completely all 
acid fermentation, and then treated with different amounts of 
lactic acid. After standing one hour, with occasional shaking, 
the curd in the different flasks was extracted, first with small 
amounts of water and then with 500 cc. of 5 per ct. solution of 
sodium chloride. In 50 cc. of each of these extracts, the nitrogen 
was determined by the Kjeldahl method. The results are given 
in the following table: 
TABLE VI.—AMouNTS OF SALT-SOLUBLE COMPOUND FORMED BY 
DIFFERENT AMOUNTS OF ACIDS. 


Grams of lactic acid used.......... 0 0.02) 0.05} O. 101 0.20 0.50 
Percentage of total nitrogen in form 
of salt-soluble compound........ 6.0 | 7.0°) 8:1.) 8.05) 2370 eens 



The amount of salt-soluble compound was not proportionately 
increased by the use of .02, .05 and .10 gram of lactic acid for 
25 grams of curd; but when an additional .10 gram of lactic acid 

