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XL. The Influence of the Size of Colloid Particles upon the 

 Adsorption of Electrolytes, By Humphrey D. Murray, 



Exhibitioner of Christ Church, O.vford*. 



^EVERAL workers have examined the influence of con- 

 k^ centration upon the coagulation of colloidal solutions, 

 hut references to the effect produced by alteration in the 

 degree of dispersion are few and not very definite. Kruyt 

 and Spek t examined the coagulation of colloidal arsenious 

 sulphide, and found that the coagulative value of univalent 

 ions increased with increasing dilution ; in the case of a 

 divalent ion there was a slight decrease ; whilst for a ter- 

 valent ion there was a rapid decrease in the coagulative 

 value. Burton and Bishop + examined the coagulative 

 values of various ions upon colloidal solutions of arsenious 

 sulphide, copper, and gum mastic, and as the result of their 

 experiments found that with univalent ions the concentration 

 of the ion required for coagulation increased with decreasing 

 concentration of the colloid, for divalent ions the concentra- 

 tion of the ion was nearly constant, for trivalent ions the 

 concentration of the ion varied almost directly with that of 

 the colloid. More recently YVeiser and Nicholas § have 

 extended these researches to colloidal solutions of hydrous 

 chromic oxide, prussian blue, hydrous ferric oxide, and 

 arsenious sulphide. They found in the case of the first three 

 that the coagulative values of electrolytes tended to 

 increase with dilution of the colloid, but the increase was 

 less marked with electrolytes having univalent precipitating 

 ions, and became more marked as the valency rose. Oden 

 found that sols with ultramicroscopic particles are more 

 sen-itive to electrolytes than those containing amicrons. 



The object of these experiments was to examine the 

 influence of the size and uniformity of colloid particles upon 

 the adsorption of electrolytes as measured by the minimal 

 concentration for coagulation. For this it was necessary to 

 obtain solutions of the same colloid prepared under identical 

 conditions, but containing particles of different mean size. 

 It was decided to employ Oden's method of fractional 

 coagulation. The most suitable colloid to use, therefore, is 

 one which, when first made, contains particles of markedly 



* Communicated by the Author. 



t Kruyt and Spek,*AV/. Zeit. xxv. p. 1 (1919). 



X Burton and Bishop, Jour. Phys. Chern. xxiv. p. 703 (1920). 



§ Weiser and Nicholas, Jour. Phys. Chem. xxv. 742 (1921). 



Phil. Mag. S. 6. Vol. 44. No. 260. Aug. 1922. 2 D 



