58 



Transactioj>is of the Canadian Institute. 



[Vol. IX. 



dealt with. In the case of sols, the particles of which are negatively 

 charged, the important factor in the added electrolyte is the valency of 

 the positive (or metal) ion, while, in the case of the oppositely charged 

 particles, it is the valency of the acid radical which is the determining 

 influence. In every case the valency of the added ions bearing a charge 



PrussidnBlue. 



70O &»i 900. 



fiesistdJice (/1r/j'u), 



the same in sign as that of the particle does not seem to have the slightest 

 effect on the power of the electrolyte to produce a decrease in the value 

 of the velocity of the particle in an electric field and, consequently, coagu- 

 lation. 



As the particle of the ferric hydroxide is positively charged, potassium 

 phosphate was chosen because the acid radical is trivalent and therefore of 

 very great discharging power. At the end of the time recorded in Table 

 I, 5CCS. of the dialysed ferric hydroxide were mixed with 250 ccs. of con- 

 ductivity water, the mixture still giving a rather highly coloured solution. 

 The velocity of the particles was taken and then to various samples of 

 50CCS. of this solution 10, 15, 24, and 36 drops of i/iooo normal* potassium 

 phosphate were added respectively. The effect of the salt on the velocity 

 of the particles is recorded in Table III. 



*The meaning of normal here is one gram molecular weight per 1000 ccs. of water. 



