JACQUES LOEB 



259 



result. The figures indicate the number of cc. of 95 per cent alcohol 

 which when added to 10 cc. of 1 per cent gelatin solution brings about 

 the standard degree of opacity. When the addition of 30 cc. or more 

 alcohol to 10 cc. of the 1 per cent solution of gelatin-acid salt leaves the 

 solution perfectly clear we indicate this by the sign oo . 



The result (which agrees with the results of a previous publication 

 by the writer^) is unequivocal: all those gelatin-acid salts in which 

 the anion in combination with gelatin is monovalent can no longer be 

 precipitated by 95 per cent alcohol when the pH is ^ 4.4; while the 

 only gelatin-acid salt in combination with a bivalent anion, namely 

 gelatin sulfate, can be precipitated at any pH down to 2.0 (or even 

 below). The relative solubility of gelatin-acid salts in alcohol shows, 



TABLE V. 



Cc. of 95 per cent alcohol required to bring 10 cc. of 1 per cent gelatin-salt solution to standard opacity. 



therefore, the same influence of the valency (and lack of influence of 

 the nature of the anion) which we have found in connection with the 

 other properties of proteins like swelling, osmotic pressure, and 

 viscosity. 



The same agreement exists in regard to metal gelatinates. 10 cc. 

 of a 1 per cent solution of Li, Na, K, and NH4 gelatinate can no longer 

 be precipitated by the addition of 95 per cent alcohol when the pH 

 is ^ 5.0. The deviation from the isoelectric point is minute. 10 cc. 

 of 1 per cent Ba and Ca gelatinate, however, can be precipitated with 

 comparatively small quantities of 95 per cent alcohol at any pH 

 (Table V). 



5 Loeb, J., /, Biol. Chem., 1918, xxxiv, 489. 



