Chemistry. — "The Ekctvo-viscous Effect in Rubhersol." By Prof. 

 H. R. Kkuyt and W. A. N. Eggink. 



(Communicated at the meeting of January 27. 1922). 



1. Researches on agarsoPi have tanght that the relation ') between 

 the charge of dispersed particles and the viscosity of the dispersed 

 system manifests itself clearly in those sols in which the charge can 

 be considerably modified without the colloid system as such being 

 annihilated, i.e. in those ' systems of which the stability does not 

 only depend on their charge, bnt in which also hydration more 

 general: solvation) protects the system. The conceptions about the 

 stability ot the lyophile sol may be applied throughout the territory 

 of the emulsoids '), at least when water is taken as the substance 

 in which the dispersion takes place. Our attention was, however, 

 drawn by a remark on p. 570 of 0. de Vries' Estate Rubber '), 

 where it is stated that increase resp. decrease of the viscosity of a 

 benzene rubber solution is brought about by shaking it with a few 

 drops of a solution of alkali resp. of acid or salt. 



As it seems as if this is a question of an electro-viscous effect, 

 we have examined what influence electrolytes have on the viscosity 

 of solutions of rubber in benzene. 



2. Sols were used prepared in the following way : 1 gr. of a 

 certain crepe-rubber was added to 300 cm. of benzene, after 24 hours 

 it was carefully shaken, and the sol was poured through a folded paper 

 filter. Then benzene solutions of the electrolytes were made ; the liquids 

 which were to be examined viscosimetrically, were prepared by 

 mixing a volume of sol with a volume of the solution of the electrolyte 

 (resp. a volume of benzene, for the zero-standard) ; or as far as the measu- 

 rement of rubberless liquids are concerned by diluting electrolyte solutions 

 with benzene, as they were diluted with sol just before. At the 



>) H. R. Krutt and H. G. de Jono, Z. physik. Chem. 100, 250 (1922). 



') M. VON Smoldchowski, Koll. Z. 18, 190 (1918). We prefer the term electro- 

 viscous to quasi-viscous, which v. Smoluchowski uses, but which may give rise to 

 misunderstanding. 



») H. R. Krdyt, Koll. Z. 31, 338 (1922). 



*) Batavia 1920. 



