W. O: Fenn 443 
ous electrolytes when each is used alone are quite different and 
their dilution curves are so dissimilar that the additive effects are 
difficult to determine. When the additive effect is not known, 
it is safe to say that antagonism exists if the observed effect is less 
than that produced by the most strongly acting electrolyte in the 
absence of the others (and in the same concentration in which 
it exists in the combination). When the observed effect is 
greater than this, there may still be some antagonism but it is 
very slight. This criterion will, therefore, be used throughout 
this paper in determining’ whether or not two electrolytes are 
antagonistic in their effects. 
Returning to Fig. 1, the conclusion may be drawn that acetic 
acid is antagonized by sodium salts, the bivalent SO, ion and the 
trivalent citrate ion being most effective, and the acetate, which, 
like the citrate, yields an alkaline solution by hydrolysis, being 
more effective than the nitrate or chloride. 
This experiment. (Fig. 1) was designed to elucidate by means 
of gelatin an experiment of Loeb,” where 0.125 ™m sodium salts 
was found to prevent the penetration of acetic acid into the egg 
of Fundulus. The order of effectiveness found by Loeb was 
SO.> acetate, Cl> NO. 
The relations of NasSO, to acid and alkaline gelatin are illus- 
trated in Fig. 2. In this experiment the effect of increasing 
concentrations of NaeSQ, on gelatin dissolved in HCl, NaOH, 
and water was determined by the alcohol method. The effect of 
Na,SO, on gelatin plus HCI is found to pass through a minimum. 
This minimum is probably an isoelectric point due to the neutrali- 
zation of the effect of the H ions by the SO, anions. The pro- ~ 
portions of SO, to H at this point are as 100:30. Antagonism 
is shown by the fact that the combined effect of NagSO, and 
HCl at the minimum is less than that of the HCl alone. NagSO, 
and HCl are, therefore, antagonistic in their effects on gelatin, at 
least in certain concentrations. 
The effect of NasSO, on gelatin plus NaOH is seen (Fig. 2 and 
Table II) to pass through a maximum and subsequently fall off. 
The effect of Na:SO. alone is shown in the dotted line. At no 
point is the combined effect of NasSO, and NaOH less than the 
effect of either alone. Therefore in low concentrations at least 
18 Loeb, J. Biol. Chem., 1915, xxiii, 139. 
