6o Transactions of the Canadian Institute. [Vol. IX. 



according to the Hardy-Linder-Picton law. By adding gradually in- 

 creasing amounts of these salt solutions to samples of the colloidal 

 solution, it was found that the coagulative power of these solutions was 

 practically the same, thus bearing out the truth of the above law. 



d. Summary. 



From the above results we may conclude that : 



1. As the ferric chloride is removed from a colloidal solution of ferric 



hydroxide, the charge on the particle at first increases, reaches a maximum, 

 then gradually decreases. 



2. The trivalent phosphate ion has a strong discharging and coagula- 

 tive action on these colloidal particles. 



3. Coagulation experiments on samples of dilute dialysed ferric hy- 

 droxide seem to bear out the truth of the law due to Linder, Picton and 

 Hardy. 



In conclusion, I desire to thank Dr. M. C. Boswell for the chemical 

 analyses. 



Department of Physics, University of Toronto, 

 June 2oth, 1910. 



