THE EFFECTS OF ELECTROLYTES ON GELATIN AND 
THEIR BIOLOGICAL SIGNIFICANCE. 
II. THE EFFECT OF SALTS ON THE PRECIPITATION OF ACID 
AND ALKALINE GELATIN BY ALCOHOL. ANTAGONISM. 
By W. O. FENN. 
(From the Laboratory of Plant Physiology, Harvard University, Cambridge.) 
(Received for publication, January 14, 1918.) 
In a previous paper! the writer described a method for study- 
ing the effects of electrolytes on gelatin which was found ,to pos- 
sess many advantages. It consisted essentially in adding 95 per 
cent alcohol to 5 cc. of a gelatin-electrolyte mixture until an 
opaque precipitate was produced. The number of cc. of alcohol 
required to produce this precipitate was referred to as the ‘‘alco- 
hol number” of gelatin. It can be quickly and accurately deter- 
mined and is surprisingly sensitive to small variations in the 
electrolyte content. 
The separate effects of acids, alkalies, and salts on the alcohol 
number of gelatin have already been described. The present 
paper deals with the effect of salts when combined with acids and 
alkalies. The effect of mixtures of two salts will form the subject 
of a later paper. 
There is need in biology for a complete knowledge of the 
equilibrium between salts and acid proteins or alkaline proteins, 
especially in view of the antagonistic action of salts and acids 
in their effects on organisms, as described by Loeb,? by Osterhout? 
and by others. Thereis no evidence of antagonistic action between 
salts and alkalies in biological work, so far as the writer is aware. 
Instances of antagonism between salts and both alkalies and acids 
are, however, numerous in investigations on the physical chem- 
istry of protein solutions. 
1 Fenn, W. O., J. Biol. Chem., 1918, xxxiii, 279. 
2 Loeb, J., Arch. ges. Physiol., 1899, Ixxv, 308. Loeb, J., and Waste- 
neys, H., Biochem. Z., 1911, xxxili, 489; 1912, xxxix, 167. 
3 Osterhout, W. J. V., J. Biol. Chem., 1914, xix, 517. 
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THE JOURNAL OF BIOLOGICAL CHEMISTRY, VOL. XXXIII, NO. 3 
