W. O. Fenn 445 
NaOH and NapSO, are not antagonistic. Their relations in higher 
concentrations are like those for Na; citrate and NaOH in Fig. 3. 
To determine the effects of higher concentrations of Na; citrate 
and NaOH on gelatin, the effect of increasing concentrations of 
Nas; citrate was determined for gelatin made up in water, and in 
six concentrations of NaOH. The results for four of these con- 
centrations and for water are plotted in Fig. 3 (see Table III). 
The: concentrations of Na; citrate used are plotted on the ab- 
scisse and the concentrations of NaOH simultaneously present ‘ 
in the gelatin are inserted on the curves. In the concentrations 
of NaOH chosen, no precipitate could be produced with alcohol 
unless Na; citrate was also present in sufficient amount. The 
more Naz citrate there is present the easier it is to precipitate. 
This shows antagonism. At points A and B, moreover, the com- 
bined effect is less than the effect of either Naz citrate or NaOH 
alone in those concentrations. An examination of the ordinates 
at B shows that small amounts of NaOH increase the alcohol 
number of gelatin plus Na; citrate, but larger amounts decrease 
it. This is in agreement with the fact that small amounts of 
NaOH hinder the precipitation of gelatin by NasSO, and Nas 
citrate, while larger amounts favor it.4 Conversely, it may be 
inferred from this figure, taken in conjunction with the expéri- 
ments in Fig. 2, that small amounts of Na,SO, or Nas citrate 
increase the aicohol number of gelatin plus NaOH, while higher 
concentrations decrease it. 
From this experiment the conclusion may therefore be drawn 
that NazSO, and NaOH are not antagonistic in weak concentra- 
tions (of both) but that they are antagonistic in higher concentrations. 
In Fig. 4 and Table IV are shown the effects of increasing con- 
centrations of CaCl, on the alcohol number of gelatin dissolved 
in water, NaOH, and acetic acid. In NaOH, the curve passes 
through a sharp minimum. This is due in part at least, to the 
formation of Ca(OH):, a small amount of which precipitated. 
It is probable that there is also some residual antagonistic effect 
upon the gelatin. In their relations to alkaline gelatin MgCl, 
and AICI, behave like CaCl, the curves passing through similar 
minima. In acid gelatin, however, MgCl, behaves more like 
14 Figures for this will appear in a subsequent paper on the precipita- 
‘tion of gelatin by mixtures of electrolytes. 
