W. O. Fenn 447 
NaC] because it fails to give the sharp maximum which CaCl, 
gives in its effect on acetic acid-gelatin, as shown in Fig. 4. 
A sharp maximum like that shown for CaCl plus acetic acid 
has been shown to be characteristic of the effects of acid alone 
on the alcohol number of gelatin. It is not found in the pure 
CaCk curve as’ shown by the dotted line. Furthermore, an ex- 
amination of these curves reveals the fact that at no point is the 
combined effect of CaCl. and acetic acid less than the effect of 
either CaCl, or acetic acid alone. CaCl, and acetic acid, at 
~ least in small concentrations, are not antagonistic in their effects. 
TABLE III. 
Effect of Sodium Citrate on the Alcohol Number of Gelatin plus NaOH. 
Conenerhs Ce. alcohol to precipitate in gelatin plus NaOH. 
tion o 
Nascitrate.! 99 4 | 0.0235m [ 0.047 0.094 0.127 u 0.254 u 0.508 u 
M 
0.28 5.4 7.0 6.5 G0 6.6 6.1 5:6 
0.14 8.8 9.7 9.6 8.9 8.9 4.9 7.1 
0.07 10.0 14.7 foo7- 12.4 13.6 L007 9.4 
0.035 10.9 24.4 22.0 17.8 16.5 ‘14.6 12.6 
0.0175 | 11.5] No ppt.] 30.0+) No ppt.| 22.7 22.8 17.8 
0.0087 | 10.7| “ “ |Noppt.| “ “ | 32.0+] 30.0 30.0 
0.0043 ; hive Ge Sa eNoippt.-No ppte) No ppt: 
0 0 4. 5 ¢¢ “ “ce cc (79 “ (<3 (<9 (<9 “ce iT (<4 
2 per cent gelatin A for 15 to 20 hours at 30°C. before adding alcohol. 
Other details asin Table I. (See Fig. 3.) 
In higher concentrations of CaCl, however, it is antagonistic 
to acids. Thus Fig. 5 and Table V show that acetic acid com- 
pletely prevents the precipitation of gelatin by alcohol in con- 
centrations greater than 0.1 m (see dotted line in the H2,O curve) 
but that when CaCl, 1.5m is also present, precipitation is pos- 
sible even in high concentrations of acetic acid. A comparison 
of this result with the acetic acid curves in gelatin plus sodium 
salts (Fig. 1) shows that although CaCl, does antagonize acids 
it is very much less effective in this respect than are the sodium 
salts, particularly those with polyvalent anions, 
In low concentrations, therefore, CaCl, 1s not antagonistic to 
acids but in higher concentrations tt 1s. 
