Jacques Loeb Dot 
(1) Gelatin-Cl + Nat 
oh 
(2) Gelatin-Na + Cl- 
+ = 
(3) Gelatin + Nat + Cl- 
_ + 
In (1) gelatin ion would be negative, in (2) gelatin ion would 
be positive, and in (3) the gelatin ion would have both a nega- 
tive and a positive charge in different parts of the molecule. 
We shall see that the facts speak in favor of (1); namely, an ex- 
clusive or a prevailing formation of negative gelatin ions. Ac- 
cording to our assumption the additional swelling of gelatin due 
to ionization should begin when the salt solution used for per- 
fusion to wash out the m/8 NaCl is so dilute as not to suppress 
the electrolytic dissociation of the gelatin-salt compound com- 
pletely. Since this suppression depends upon the common ion of 
the gelatin-salt compound and the salt, it should be possible to 
ascertain which this common ion is, the anion or the cation of 
the salt. If, for instance, the dissociation of the gelatin salt 
occurs according to (1) into gelatin + Nat, the lowest concen- 
tration of NaeSO, which just allows the additional swelling of 
a gelatin previously treated with m/8 NaCl should be about 
one-half of that in which the swelling begins when lower con- 
centrations of NaCl are used; since, e.g., a M/256 NasSO, solution 
sends about twice as many Na ions into solution as does a M/256 
NaCl solution. In other words, that concentration of a salt 
which is just able to inhibit completely the subsequent swelling 
of gelatin previously treated with m/8 NaCl should depend 
only upon the concentration of the cation of this salt, if the type 
(1) of the dissociation of the gelatin salt exists; namely, 
> + 
(1) Na-gelatin — gelatin + Na 
This is the case. We know from Table I that the inhibiting 
concentration of NaCl for the additional swelling" of gelatin pre- 
viously treated with m/8 NaCl is m/64 NaCl. In this concen- 
11 By additional swelling we mean the swelling which takes place as a 
consequence of the previous. treatment with M/8 NaCl, when the excess 
of the salt is removed and the ionization of the gelatin salt no longer 
too much depressed. 
