264. REpPorRT OF THE CHEMIST OF THE 
pared by us from cheese-curd and cheese. This is the body 
which our former work led us to regard as a compound formed 
by combination of paracasein and lactic acid in the case of cheese 
and which we regarded as paracasein monolactate. As the result 
of our more recent work, we now believe that the compound 
formed by treating calcium paracasein (cheese curd) with an 
amount of acid just sufficient to combine with the calcium of the 
calcium paracasein, in addition to certain inorganic salts held 
mechanically in the cheese-curd, is not paracasein mionolactate 
but base-free paracasein, or calcium paracasein from which the 
calcium has been removed by its combination with acid. 
THE RELATION BETWEEN THE TWO SERIES OF COMPOUNDS PREVIOUSLY 
CALLED PARACASEIN MONO-SALTS AND PARACASEIN DI-SALTS. 
When to the base-free paracasein we add dilute acid, another 
body appears to be formed, which differs in properties from the 
base-free proteid in being insoluble in warm 5 per ct. salt solution 
and hot 50 per ct. alcohol, and also in possessing none of the 
peculiar plastic properties of the base-free paracasein. This sub- 
stance is formed when milk is treated with rennet enzym and 
allowed to coagulate either by spontaneous souring or by the 
direct addition of dilute acids. We at first regarded this sub- 
stance as a paracasein di-salt of an acid, but since we have 
shown that what we regarded as a paracasein mono-salt is 
the base-free proteid, paracasein, we now regard this compound 
as resulting from the combination of acid with the base-free 
paracasein, forming a paracasein salt of the acid used, corre- 
sponding to the casein salts of acids, which have been already 
discussed. 
In each -of several experiments we suspended in distilled 
water portions of .5 gram of base-free paracasein and treated this 
with varying amounts of dilute acid of different strengths, agi- 
tating from time to time for an hour. The mixture was filtered 
and the filtrate titrated with _- hydrochloric acid. The 
amount of acid not recovered in the filtrate is regarded as repre- 
senting approximately the quantity that had combined with the 
paracasein. This was found to be equivalent to about 0.5 ec. of 
; hydrochloric acid, closely agreeing with the results obtained 
by treating base-free casein with acid. 
