CHAPTER XIII 



CERTAIN PHYSICAL PROPERTIES OF PROTEIN SOLUTIONS, ETC. 



1. The Viscosity of Protein Solutions. — Protein solutions are 

 usually characterized by the possession of a high viscosity. The 

 question has been raised whether the viscosity is similar in nature 

 to that of a solution of a crystalloid substance, or whether it is 

 not, rather, comparable with the viscosity of a suspension of solid 

 particles (40). In support of this latter view it has been pointed 

 out that Bottazzi's measurements of the influence of concen- 

 tration upon the viscosity of protein solutions indicate that the 

 viscosity of these solutions does not change continuously with 

 change in concentration, as it does in solutions of crystalloids, but 

 changes per saltum (12). The measurements of Bottazzi were 

 made upon relatively few and widely separated concentrations, 

 however, and subsequent observers have not confirmed his results 

 (108) (59). Thus Sackur finds that the viscosity of solutions of 

 the "basic" caseinates of sodium and ammonium (i.e., containing 

 about 80x10"^ equivalents of base per gram and neutral to 

 phenolphthalein) varies with the concentration according to the 



Arrhenius-Euler formula — = A", where ?? is the viscosity of the 



solution, 770 that of the solvent, n is the concentration of the solu- 

 tion and ^ is a constant, the numerical value of which depends 

 upon the nature of the dissolved substance and upon the tempera- 

 ture (2). The following are Sackur's results: 



A remarkable feature of these results is the extraordinarily high 

 value of A, involving a very rapid increase in viscosity with 



320 



