REPORT OF THE CHEMICAL DEPARTMENT. 
Peete ehlONt OP DIU ThE ACIDS: UPON 
CASEIN WHEN NO SOLUBLE COM- 
BOWEN io hore PONE Dee 
L. L. VAN SLYKE AND D. D. VAN SLYKE. 
3 SUMMARY. 
1. Object The work of which an occount is presented was 
undertaken primarily to measure more accurately the amount of 
acid that combines with casein to form a definite compound in- 
soluble in water, but facts were developed which raised the funda- 
mental question as to whether the action is one of real chemical 
combination and to this question chief attention is directed. 
2. Outline of method of work.— Casein is agitated with dilute 
acids of known strength for given periods of time, the mixture is 
filtered and the amount of acid taken up by the casein 1s measured 
by the decrease in the conductivity of the solution. It was found 
necessary to work out special formulas in order to calculate con- 
veniently the results of conductivity measurements into terms giv- 
ing equivalent amounts of acid. In some cases, casein that had 
taken up acid was treated with water and the acid partially ex- 
tracted. 
3. General scope of work.— The behavior of casein was studied 
(1) with four acids of different dissociating power (hydrochloric, 
sulphuric, lactic and acetic) ; (2) with N-125, N-500, N-1ooo and 
N-2000 concentrations of these acids; (3) for contact of different 
periods of time, ranging from 5 minutes to 48 hours; (4) at dif- 
ferent temperatures (O°, 25° and 45° C.); and (5) with dilute so- 
es yD 
*Reprint of Part I, Technical Bulletin No. 3. 
[203] 
