590 



Mr. E. F. Burton on the Action of 



It will be noticed from the table, that at first the addition 

 of KC1 produced a slight increase in the velocity, but as 

 larger amounts were added the velocity reached a maximum 

 and then slowly decreased. It is important to observe that 

 in the above samples there was no sign of" coagulation even 

 at the expiration o£ several weeks. Two of the solutions did 

 coagulate at the end of six weeks, but this interval is so long 

 that this result may have been due to some ulterior cause. 



b. Potassium Sulphate. 

 Similar results for this salt, a ^qq (gram-molecular) solu- 

 tion of which was used, are given in Table VI. 



Table VI. 

 K 2 S0 4 added to Copper Colloidal Solution. 



No. 



Grams of S0 4 per 

 50 ccs. Cu Sol. 



Spec. Cond. 

 at 18° C. 



Velocity at 



18° C. 



Coagulation. 



1 







3-6 X10" 5 



8-9X10" 5 



17-8X10" 5 



44-5X10 -5 



71-2X10" 5 



5-8X10 -6 

 9-3X10 -6 

 12-4 xlO" 6 

 18-7X10 -6 

 385 XlO -6 

 58-3 XlO -6 



+25-4XKT 5 

 +25-3X10" 5 

 +24-0X10" 5 

 +21-8X10" 5 

 + 14-4X10" 5 

 



No sign. 



In two weeks. 

 In two hours. 

 In one hour. 



2 



3 



4 



5 



6 





When more KC1 and K 2 S0 4 than the greatest amounts 

 shown in the above tables was added to 50 ccs. of the 

 colloidal solution, the conductivity became so large that the 

 current through the liquid spoiled the velocity readings. 



c. Aluminium Sulphate. 

 In similar experiments on colloidal gold and silver solu- 

 tions from 18 XlO" 5 to 25 x 10" 5 gram of A1 2 (S0 4 ) 3 per 

 100 ccs. of colloidal solution was sufficient to reduce the 

 velocity of the gold and silver particles to zero. The very 

 strong action of this salt was attributed to the trivalent 

 aluminium ion. According to the theory then suggested, 

 this salt should not have nearly so strong an action on the 

 copper colloidal solution on account of the fact that the 

 copper particle bears a positive charge, and therefore the 

 active ion in the aluminium solution will be the S0 4 . The 

 results given in Table VII. confirm this view entirely. 



