VISCOSITY 323 



crystalloids is diminished by gelatin jellies, and the degree of 

 hindrance is materially modified by the presence, within the jelly, 

 of other dissolved substances, but the hindrance is extremely small 

 in comparison with the enormous viscosity of the jellies. 



Similarly Reformatzky (90) has shown that the velocity with 

 which methyl acetate is decomposed by acids in agar jelly (i.e., the 

 number of molecular collisions per second) is within 1 per cent of 

 its value in pure water. 



Lodge (65), Whetham (129) (130) and Masson (69) have shown 

 that the specific mobilities of the majority of inorganic ions is the 

 same in agar jellies as it is in water. Dumanski (28) has shown 

 that if allowance be made for the diminution in the cross-section 



of the conducting field, due to the presence of gelatin ( = ( - ) ' 



where g is the number of grams of gelatin per gram of solution and 



c the specific gravity of gelatin) the conductivities of inorganic 



salt solutions in gelatin jellies are very slightly less than those of 

 equally concentrated solutions in pure water. 



We have seen* that the dependence of the conductivity of 

 protein solutions upon their dilution is of perfectly normal char- 

 acter, resembling the dependence of the conductivity of a crystal- 

 loidal electrolyte upon dilution, despite the fact that the protein 

 solutions, as the above-cited results of Sackur reveal, vary enor- 

 mously in their viscosity with dilution. 



On the other hand, the intimate dependence of the conductivity 

 of solutions of electrolytes upon the ordinary type of viscosity has 

 been commented upon and quantitatively estimated by a host of 

 observers, among whom Walden may be especially mentioned 

 (127) (51) (37). Viscosities, very much less than those of the 

 dilutest jellies, profoundly diminish the conductive power of 

 electrolytes. Nor must it be imagined that the viscosity of a 

 protein jelly is essentially different, in any respect save magnitude, 

 from that of a protein solution, for, as von Schroeder (110) has 

 shown, the viscosity of a solution of gelatin, cooled below the 

 gelation-point, increases progressively and regularly with time, 

 until the extremely viscous solution passes insensibly into a jelly. 



Not only inorganic, but also protein ions are profoundly in- 

 fluenced in their mobilities by the type of viscousness which 



* Cf. Chap. X, also W. B. Hardy (41). 



