﻿the Kinetics of the Process of Coagulation. 317 



Kruyt and Arkel *, working with selenium sol and very 

 slow rate of coagulation, find extremely wide variations in T 

 in the same experiment. 



Table IX. 



(Observers : Kruyt and Arkel.) 



Values o£ T (in hours) . 



I. 



II. 



III. 



IV. 



2-8 



200 



131 



1-3 



51 



390 



55 



34 



44 



270 



52 



2'2 



(43) 



320 



54 



43 



(157) 



600 



68 



105 



200 



- 370 



55 



40 



— 



510 



— 



— 



— 



440 



48 



37 



— 



— 



— 



52 



__ 



_ 



— 



38 



The above few instances will suffice to show the range of 

 variations in u T " during the course of one experiment that 

 has been observed in the ultramicroscopic measurements. 



Considering that in Tables Y. to VII. the ratios between 

 the different values of T are taken, the range of variation 

 is extremely small. The actual deviations in the value of T 

 in any one experiment must be much less than the extreme 

 variations given. This comparison leaves no room for doubt 

 that " T " is a constant in the case of gold sols and within 

 the limits of the rate of coagulation that have been studied. 

 In fact, these data constitute the best evidence so far recorded 

 in favour of the theory of Smoluchowski. 



The Dependence of € on the Concentration. 



Tables V. to VII. show clearly how rapidly e, the 

 percentage of successful collisions, increases with con- 

 centration. A change of concentration in the ratio 24 

 to 28 increases the rate in the ratio 1 : 11 or 1:6 as the 

 case may be. It would be extremely interesting to work 

 with a sol which is less susceptible to impurities than these 

 gold sols. 



* Fee. Trav. CLim. Pays-Bas, vol. xxxix. T4] p. 6o(i (1920) ; [4] 

 vol. xl. p. 169(1921). 



