232 REPORT OF THE CHEMIST OF THE 
Taste VII.— SHowING EFFECT OF TEMPERATURE AND CONCENTRATION UPON 
RATE OF SOLUTION OF CASEIN BY SULPHURIC AND AcETIc ACIDS. 
(Figures show results of xanthoproteic test only.) 






TIME SULPHURIC ACID. ACETIC ACID. 
OF 
CONTACT. |/ 7195) | N-500 N-1000 N-125 N-500 N-1000 
5 25°C | O°C | 25°C | O°C | 25°C || OPC | 25°C | OPC | 25°C | OPC | 25°C 
PS eeriitiees 5 beer eee) sae ieee BOF On eal! PSO CTE Cee Sia aa aes 
ENSyGanabaleicn pete Ae ee te [Pees 0 Ont eee Be Pes elas lle. O 
Salad als chet ey Se DINE, POE Ie ede Logi eaves Ae oe RS REE Ap 0 
SEDER: ey es Ae 4 0 2 0 1 1 1 Oilers 0 0) 
LDS ES esr en Skene fae, eee OTA She ek ok De altne ete Onc) see 0 0 
24 ESR eee anne he La goers LSPs Pee. PAT ea Os) See O cies 













The results embodied in Tables V, VI, VII are summarized 
as follows: 
(1) Comparing hydrochloric and lactic acids, it is seen that these 
two acids have about the same solvent power at 0° C. with the 
higher dilutions, but with N-125 acid the solvent power of the 
lactic acid is somewhat greater. Increase of temperature increases 
the solvent effect of lactic acid less than that of hydrochloric. 
(2) Sulphuric acid dissolves casein more slowly than does hydro- 
chloric acid of the same strength and at the same temperatures. 
(3) Acetic acid is distinguished for its comparatively slight sol- 
vent action on casein at ordinary temperature. This fact is of 
interest in connection with the method of separating casein from 
milk by precipitation with acetic acid, the method in general use. 
Its use involves a more complete separation under uniform condi- 
tions, and with less solvent action, than can be attained by use of the 
other acids studied. 
(4) In order to study the effect of the acids under consideration 
upon casein without dissolving appreciable amounts of casein, it is 
necessary to use acid solutions as dilute as N-500 to N-2000 and at 
temperatures not above 25° C. 
Action of neutral salts upon the solubility of casein—In order 
to test the effect of replacing the H+ ion, casein was treated at 
room temperature with N-125 MgSO, and with N-s50 KCl, the 
same method of treatment being used as with the acids. Even 
after constant agitation of casein with magnesium sulphate for 
6 hours and with potassium chloride for 28 hours, we were unable 
to obtain any evidence of soltition of casein. 
