284 Effects of Electrolytes on Gelatin. I 
von Schroeder’s maximum viscosity. It is difficult to understand 
this unless Ostwald has confused the “hydration viscosity” as 
measured by von Schroeder in dilute solutions with the “gela- 
tion viscosity’”’ of solutions which are strong enough to set. The 
gelation viscosity is of course at a maximum in an approxi- 
mately neutral solution. It is evident that Ostwald’s minimum 
must be some secondary phenomenon inherent in the swelling 
method. 
The equilibrium between proteins and acids has been studied 
in more detail by other methods. Bugarsky and Liebermann” 
and Manabe and Matula® have made simultaneous electrometric 
determinations of the H and Cl ions combined with the protein 
in HCl. The amount of HCl combined with the protein has been 
determined by Van Slyke by conductivity measurements, and 
the amount of the H ion combined has been determined by 
Pauli and Hirschfeld® and by Procter® by potentiometer measure- 
ments of the H ion concentration. The latter has made perhaps 
the most notable contribution to the subject by giving a quanti- 
tative explanation of the maximum swelling of gelatin in acids. 
b. Salts. 
The following conclusions can be drawn concerning the effects 
of salts on the alcohol number of gelatin. (1) All salts increase 
the alcohol number of gelatin except certain ones which combine 
a bivalent or trivalent cation with a bivalent or trivalent anion. 
(2) Trivalent anions and cations are more effective than biva- 
lent, and bivalent are more effective than monovalent in hinder- 
ing precipitation. (8) The lyotropic effect is of minor impor- 
tance except in high concentrations of sulfates, citrates, and 
tartrates. 
The results of the experiments with salts alone are plotted in 
Figs. 2 to 5 and the data are given in the corresponding tables. 
In all cases the ordinates represent the number of ce. of alcohol 
required to produce a precipitate in 5 cc. of the gelatin-salt mix- 
2 Bugarsky, 8., and Liebermann, L., Arch. ges. Physiol., 1898, xxii, 51. 
13 Manabe, K., and Matula, J., Biochem. Z., 19138, lii, 369. 
14 Van Slyke, L. L., and Van Slyke, D. D., Am. Chem. J., 1907, xxxviii, 
383. 
15 Pauli, W., and Hirschfeld, M., Biochem. Z., 1914, Ixii, 245. 
