112 THE ROYAL SOCIETY OF CANADA 



^«^^80 = 50.1683 CCS. 



1 . 0038 

 .*. \^olume occupied by solid particles in bottle full of solution 



vi = z;- — =50.2024-50.1683=0.0341 cc. 

 a 



.'. If x= density of theyl^2'S'3 particles 



lih 0.1176 



""" 7i"(M)3ll"^-^^- 



On looking up the mineral tables* of densities we find that arsenious 

 sulphide is given as between 3 .4 and 3.5. 



This seems to be quite conclusive evidence that the ultimate 

 structure of the particles is not of a loosely packed, spongy nature 

 but is as compact as the sulphide in large masses. 



Summary 



A method is given by which the centrifuge may be made to 

 hasten the coagulative action due to adding electrolytes to colloidal 

 solutions, so that such determinations of coagulating power of electro- 

 lytes m.ay be both hastened and standardized. Incidentally a deter- 

 mination of the density of the arsenious sulphide in colloidal solution 

 is shown to be the same as that of the substance in large masses. 



Department of Physics, 

 Universitv of Toronto. 



* Dana: Textbook of Mineralogy, Ed. 1916, p. 282. 



