Mr. W. Sutherland on Weak Electrolytes. 17 



was employed at longer ranges. The explanation appeared 

 at first to be simple, and the increased value of fju was attri- 

 buted to the ft rays from radium B. I found, however, that 

 this large value of the coefficient of absorption persisted from 

 14 to 90 minutes after the thin foil was removed from the 

 radium emanation, during which time the proportion of 

 radium C to radium B was increasing. This point requires 

 special investigation, but at present it appears that radium C 

 emits a considerable proportion of slow j3 rays, comparable 

 to those from radium B. 



The active deposit of thorium was examined for distances 

 from 20 to 30 cm. from the centre of the electroscope. In 

 this case the /5 rays from Th A and Th D pass into and through 

 the electroscope. The value of jjl for air was between *024 

 and '025, but the intensity of the radiation at ray disposal 

 was insufficient for a good determination, and further mea- 

 surements are in progress. 



III. On Weak Electrolytes and towards a Dynamical Tlieory 

 of Solutions. By William Sutherland "*. 



rj^HE chief defect of the prevalent theory of solutions is its 

 -L want of a dynamical foundation. This can be com- 

 pletely removed only when we have a kinetic theory of 

 liquids as adequate as the kinetic theory of gases. Mean- 

 while the valuable inductions associated with the names of 

 Arrhenius, Ostwald, van't Hoff, and others are interpreted 

 by the simplest chemical theory that will explain them, the 

 manifest physical difficulties being simply ignored. Hence 

 has arisen the critical attitude of physicists like Kelvin and 

 Helmholtz towards the working hypotheses of a large part 

 of theoretical physical chemistry. Take for instance the 

 principle of partial ionization as applied to the simplest case 

 of a binary electrolyte like NaOl in water. It is assumed 

 that the degree of ionization is controlled entirely by the 

 law of mass action, the ionizing force of the water and the 

 electrical attractions of the oppositely charged ions for one 

 another being completely ignored. One result of this 

 method of proceeding is to reach a theoretical conclusion 

 which is not verified for a typical electrolyte like NaCl. 

 Another result, however, is to find the theoretical conclusion 

 beautifully verified in the case of electrolytes like acetic 

 acid. The expounders of the prevalent theories of physical 



* Communicated by the Author. 

 Phil. Mag. S. 6. Vol. 22. No. 127. July 1911. (J 



