442 Effect of Electrolytes. II 
high concentrations of acetic acid. NaCl, for example, has, 
therefore, decreased the effect of acetic acid on the alcohol num- 
ber of gelatin. But acetic acid has increased the effect of NaCl. 
Is this, then, a case of antagonism? 
Osterhout has defined two electrolytes as antagonistic when 
their combined effect is less than the additive effect, the additive 
effect being the effect of the combination if each salt acts inde- 
TABLE I. 
Antagonism between Acetic Acid and Sodium Salts in Their Action on the 
Precipitation of Gelatin by Alcohol. 
Concentra- Ce. alcohol to precipitate in gelatin plus 
tion 
of acid. H20 NaCl NaNOs3 Na acetate. Naz2SOu Na citrate. 
M 
4.17 No. ppt. 16.2 14.35 13 4.7 9.3 
2.08 ¥ 15.4 15.4 12.0 6.1 9.0 
1.04 He “s 14.4 13.9 10.4 6.6 8.2 
0.52 % 12.8 12.4 9.0 6.8 ries! 
0.26 14.35 11.2 10.9 7.9 6.9 7.4 
0.13 10.95 9.75 9.55 Toe 7.0 7.9 
0.065 8.85 8.8 8.6 7.0 7.1 7.8 
0.032 1,8 7.9 7.8 6.8 Ven 8.0 
0.016 6.15 | 
0.008 9.15 
0.004 4.5 
0.0 4.25 6.85 6.75 7.0 Al 8.7 
The first column shows the concentration of the acetic acid in the gela- 
tin before adding alcohol. The succeeding columns show the number of 
cc. of 95 per cent alcohol which were necessary to produce a precipitate 
in 5 cc. of the acetic acid solution plus H.O-gelatin, NaCl-gelatin, etc. 
In all cases the salt concentration was kept constant at 0.125 mM, while the 
concentration of acetic acid varied. 3 per cent gelatin B was used through- 
out, and all the tubes stood over night at 26°C. before adding alcohol. 
The results of two determinations were averaged for each point. (See 
Fig. 1.) 
pendent of the presence of the other.2 This is of course the 
ideal criterion for antagonism. In the case of gelatin, however, 
it is frequently not easy to apply because the effects of the vari- 
2 For criteria of antagonism in biological work and the determination 
of the additive effect see Osterhout, Bot. Gaz., 1914, lviii, 178; 1915. lx, 
228. 
