76 COLLOID CHEMISTRY OF THE PROTEINS 



their ionisation, which is important in determining the 

 optical rotation. We must therefore seek the explanation of 

 the differences in rotation of the protein salts in constitutive 

 differences of the protein portion of these salts rather than in 

 variations in ionisation with a common anion. It is extremely 

 probable that the widespread agreement between rotation and 

 viscosity in the series of albumin salts with various acids is due 

 to the same or, at least, similar constitutive differences exert- 

 ing their influence on the viscosity of the acid proteins. 



The very recent work of M. Adolf and E. Spiegel * on an 

 acid-albumin made by boiling dialysed ox-serum albumin with 

 dilute hydrochloric acid has shown with certainty that, when 

 the precipitated acid albumin is dissolved in increasing quan- 

 tities of hydrochloric acid, the rotation passes through a 

 maximum. Unlike natural albumin, however, of which the 

 rotation remains at the maximum level on further addition of 

 acid, with this material the value decreases in more acid solu- 

 tions until it finally sinks to the original value. 



Table 31 gives some of these results. The values of the 

 viscosity for increasing concentrations of acid are added for 

 comparison, showing the characteristic course of the curve 

 with a sharp peak at the maximum point due to repression of 

 the ionisation in excess of acid. 



Table 31. 



(Final concentration of acid-albumin, 0-62 per cent.) 



If, on the one hand, the viscosity (Table 31) and the extent 

 of combination of acid-albumin (Table 39) are compared with 

 * Biochem. Zeitsch., 1920, 104, 175. 



