296 PROPERTIES CONFERRED BY COLLOIDAL CONSTITUENTS 



A remarkable feature of these results is the extraordinarily high 

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

 concentration. For the majority of crystalloids the value of A is not 

 greatly in excess of unity, while for sodium caseinate it is of the Order 

 of 10 14 . This fact alone would lead us to suspect that the mechanism 

 which produces the viscosity of these solutions is different in nature 

 from that which produces the viscosity of solutions of crystalloids. 

 The viscosity of a protein solution is also very greatly increased by 

 lonization, the viscosity of protein solutions being at a minimum when 

 ionic protein is absent, i. e., when the protein is uncombined with acids 

 or bases. 



Indeed a very little consideration suffices to show that the viscosity 

 of a protein solution is of a very different type from the viscosity, for 

 example, of solutions of Sugar or Glycerol in water. Apart from the 

 extraordinary magnitude of A, the type of viscosity exhibited 

 by solutions of proteins differs from the viscosity of a glycerol-water 

 mixture in that it affords no hindrance, or very slight hindrance, 

 to the motion of ions and of crystalloidal molecules. The velocities 

 with which various crystalloids diffuse through Gelatin jellies are 

 remarkably close to the diffusion-velocities of the same substances in 

 distilled water. The jelly causes a very slight retardation of diffusion 

 but the hindrance to molecular movement is disproportionately small 

 in comparison with the enormous viscosity of the jellies. 



It has repeatedly been shown that the specific mobilities of the 

 majority of inorganic ions is the same in gelatin or agar jellies as it is 

 in distilled water. In fact, if allowance be made for the diminution 

 of the cross-section of the conducting field which is occasioned by the 

 presence of gelatin molecules we find that the electrical conductivities 

 of inorganic salt solutions in gelatin jellies are only very slightly less 

 than those of equally concentrated solutions in pure water, implying 

 that the ions of the electrolyte move as freely in the insterstices between 

 the protein molecules as they would move in distilled water. This is 

 true even when the ions are protein ions, for the dependence of the 

 Electrical Conductivity of protein solutions upon their dilution is of a 

 perfectly normal character, resembling the dependence of the conduc- 

 tivity of a solution of a crystalloid upon dilution, although, in the range 

 of concentrations employed, the viscosity of the protein solution 

 increases with its concentration very greatly, while that of a salt 

 solution, for example, increases almost imperceptibly. 



On the other hand the intimate dependence of the conductivities 

 of solutions of electrolytes upon the ordinary types of viscosity has 

 been commented upon, and quantitatively estimated by a host of 

 observers. Viscosities, very much less than those of the most dilute 

 Jellies, if caused by such substances as sugar or glycerol, profoundly 

 diminish the conductive power of electrolytes. Not only inorganic, but 

 also protein ions are very greatly hindered in their mobilities by the 

 type of viscousness which alcohol-water or glycerol-water mixtures 



