﻿Particles upon the Adsorption of Electrolytes. 411 



one end point for a given concentration of mastic and a given 

 electrolyte, four solutions were made up with a fairly wide 

 difference of concentration in each solution, so as to give a 

 large bracket. After standing 48 hours and centrifuging 

 for half an hoar at 2000 r.p.m., at which speed there was no 

 sedimentation of the pure mastic solution, four more 

 solutions were mode up, in which the concentrations of 

 electrolyte were such as to cover the interval between the 



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two concentrations in the first determination, within the 

 limits of which the end point was observed to lie. The 

 process was repeated until the limit of observation was 

 reached, and eventually gave two concentrations of which it 

 was possible to say that one definitely caused complete 

 coagulation, and one did not. The end point was taken as 

 the mean of these tw^o concentrations. The observation of 

 the solutions was made by daylight against a black back- 

 ground. The size of the final bracket of concentration 

 varied directly with the concentration of electrolyte necessary 

 for coagulation, and the results were therefore more accurate 

 with trivalent ions than with monovalent. The results were 

 as follows (Series 5, 6 and 7, and figs. 3, 4 and 5). 



