548 Proteins 
method the true characters of the effect of neutral salts (or any true 
effect of salts) upon the swelling of gelatin. 
The most important result obtained with our method is the 
proof that the influence of salts upon the swelling of gelatin is of 
a stoichiometrical character; z.e., we can utilize the limiting con- 
centration of different neutral salts for the additional swelling of 
sodium gelatinate to ascertain the molecular concentration of the 
salt. Experiments on the action of salt upon gelatin treated previ- 
ously with acid or alkali harmonize with the results given in this 
paper. They will be discussed in a following paper. The fact 
that dried pig’s bladder behaves similarly to the powdered gelatin 
indicates the more general character of our results. 
In the explanation of these phenomena the writer has adopted 
the idea that it is the degree of ionization of gelatin salts (of the 
type sodium gelatinate) which determines the additional swelling 
observed when the gelatin is first treated with a high concentra- 
tion of an alkali metal salt (w/8 or m/4) and the salt has been 
washed away. The reasons for this assumption are given in the. 
paper and need not be repeated here; but we may add that the 
new method and the new stoichiometric facts do not depend upon 
this hypothesis. If we adopt the ionization hypothesis, which 
seems supported by the facts known at present and contradicted 
by none, it follows, from our observations that we have at present 
two cases in which antagonistic salt action is clearly due to the 
fact that one electrolyte, e.g. NaCl or acid, causes the formation | 
of ionized protein, while the other electrolyte, e.g. CaCl, or neu- 
tral salts in general, causes the transformation of ionized into non- 
ionized protein, or inhibits in some other way the swelling effect 
of ionization of the protein molecule. The observations on the 
influence of neutral salts on the diffusion of potassium salts into — 
the egg of Pundulus may form a third case. 
SUMMARY. 
1. A new method has been described which allows us to study 
the effect. of neutral salts on gelatin. The essential part of this 
method consists in using the protein in powdered form, applying 
the salt in not too low a concentration (m/8 or M/4), and then 
washing away the salt solution. 
