88 COLLOID CHEMISTRY OF THE PROTEINS 



While the electrometric measurements show the existence 

 of an ionised salt of desamino-glutin and acid, investigations 

 of the viscosity indicate that no great increase in hydration 

 results from the formation of these protein ions. The viscosity 

 of desamino-glutin, in strong contrast with that of glutin, is 

 not increased at all by combination with acid. We must 

 therefore conclude that at least in the case of glutin the increase 

 in hydration by formation of ions is bound up with the com- 

 bination between acid and the terminal amino-groups. On the 

 other hand, the cause of precipitation of desamino-glutin is 

 clearly connected with its ionisation. Minimum precipitation 

 coincides with the maximum of ionisation, as is shown by the 

 following experiments on precipitation with phenol. 



Table 37. 



Precipitation of 075 per cent. Desamino-glutin 

 + HC1 by Phenol. 



(10 c.c. of the mixture treated with 4 c.c. of 5 per cent, phenol 



solution.} 



Thus the heavy hydration of the albumin ions is in no wise a 

 necessary preliminary to a decrease in precipitation of ionised 

 protein salts. 



According to the work of J. Christiansen* the hydrated 

 ionised albumin is most attacked by pepsin, so that the first 

 stages in the action of pepsin can be followed by noting the 

 decrease in viscosity. The heavy hydration of the particles 

 appears to be a favourable preliminary to hydrolytic decom- 



* Biochem. Zeitsch., 1912, 47, 226. 



