W. O. Fenn . 449 
TABLE IV. 
Effect of CaCl, on the Precipitation by Alcohol of Acid and Alkaline Gelatin. 
In acetic acid.* In NaOH.}j 
Ce. alcohol to precipitate in 
gelatin plus Ce. alcoho! to 
Concentration of Concentration of | precipitate in 
aCle. , : aCle. gelatin pius 
ee et MS ne NaOH, 0015 x 
M M yk Se 
1.5 15.6 16.4 0.25 9.9 
0.75 16.0 17.0 0.125 9.1 
0.375 16.7 17.8 0.0625 7.8 
0.188 17.2 18.5 0.0312 6.2 
0.094 Leo 19.5 0.0156 5.2 
0.047 18.8 21.5 0.0078 5.1 
0.024 18.6 Def OM 0.0039 6.3 
0.012 16.9 27.7 0.00195 7.6 
0.006 13.8 Fig 0.00097 8.4 
0.003 11.4 14.3 0.00048 9.1 
0.0 8.65 10.6 0.0 LEO 
*2 per cent gelatin A for 24 hours before adding alcohol. 
+3 per cent gelatin B for 15 hours at 26°C. 
The NaOH and the acetic acid curves are not strictly comparable but 
as they are so different there is no confusion in plotting them together. 
Gelatin B was not so pure a grade of commercial gelatin as gelatin A. 
Data for the effect of CaCl, on pure gelatin are given in Table II of the 
first paper of this series and are plotted with the data of this table in 
Fig. 4. Other details as in Table I. 
except in very low concentrations, it is possible. that some 
antagonism exists. AICI; is certainly less effective in this respect, 
however, than CaCh., 
In this connection, reference should be made to the conclu- 
sions of Chick and Martin!” concerning the effects of acids and 
alkalies on salts in albumin solutions. They found that small 
amounts of NaOH and HCl hindered the precipitation of albu- 
min by NaSO, and CaCl. respectively, but larger amounts 
favored it. | 
17 Chick and Martin, Biochem. J., 1913, vii, 380. 
4 
