274, REpPoRT OF THE CHEMIST OF THE 
From the results presented above, it is apparent that the reaction 
by which undissolved casein reduces the concentration of an acid 
solution is one of adsorption and not the formation of either a stable 
or a hydrolyzible salt, as is shown by the absence of either con- 
stant combining proportions or a constant concentration of acid at 
equilibrium. 
Casein is not the first proteid whose adsorptive power for acids 
has been studied. Walker and Appleyard! found that silk fixed 
varying proportions of mineral, fatty and aromatic acids, the aro- 
matic being adsorbed most completely, mineral acids next, and fatty 
acids least . and it was shown that the reaction was one of ad- 
sorption. Schmidt? found that the process by which silk fixed the 
acid dye, eosin, is one of adsorption and concluded from this and 
other data that the dyeing of silk is an adsorption phenomenon. 
Sjoqvist® found that coagulated egg albumin takes hydrochloric 
acid and sulphuric acid from solution, and that the acids could be 
re-extracted from the albumin with water, the reaction being char- 
acteristic of adsorption, although Sjéqvist attributes it a priori to 
the formation of a hydrolyzible albumin-acid salt. Using in each 
case 2 grains of albumin for 100 cc. of acid, he found that in five 
minutes, 72, 83 and or per ct. ot the actd was remwved from solu- 
tions, respectively, of N-1o, N-20 and N-4o concentration. It is 
apparent that, although the time of reaction was too short to permit 
final conclusions, the results suggest an adsorption, inasmuch as the 
concentration of the acid was reduced in all cages and more markedly 
as dilution increased, and showed no tendency towards an equilib- 
rium constant. Hardy* calls attention to the fact that the reacting 
masses of dissolved globulin and acid are not constant, and he is 
inclined to suggest the possibility that the relation between electro- 
lytes and proteids, even in solution, may be one of adsorption, the 
prteid molecules being gathered into minute masses in suspension, 
which form an “ inner phase’ more or less rich in adsorbed electro- 
lyte. Hardy emphasizes the “need for caution in regarding the 
reaction between proteids and acids as one of simple salt formation. 
‘Jour. Chem. Soc. [London], Trans., 6921334. 1806. 
*Ltschr. Phys. Chem., 15:to. 1804. 
* Skand. Arch. Physiol., 5:35. 1895. 
‘Jour. Physiol., 332300.  14u5.  fnakjht 
