Section III.. 1908- [ 37 ] Trans. R. S. C. 



V. — On the Conductivity of Mixtures of Dilute Solutions. 



By J. A. Gardiner, M.A. 

 (Communicated by Prof. J. C. McLennan and read May 26, 1908). 



Introduction. 



In a recent paper by Mr. E. F. Burton' some numbers are given 

 which shew that, when dihite hydrochloric acid was added to a 

 colloidal solution of silver, a drop in the conductivity of the solution 

 occurred. During the course of that investigation Mr. Burton also 

 observed a similar effect when dilute hydrochloric acid was added to 

 a dilute solution of silver nitrate. 



Now, according to the ionic theory of electrolysis, silver nitrate 

 in dilute solution is completely dissociated into silver and nitrate 



+ 

 ions, i.e., AgNOj becomes Ag + NO3. The same is true of hydroch- 

 loric acid in dilute solution, HCl decomposing into th,e ions H + CI. 

 Also when we add dilute HCl to dilute AgNOg we should obtain the 

 following : 



AgNOj + HCl = AgCl + Ag + CI + H + NO3. 



Since the hydrogen ion possesses greater mobility than the silver ion 

 which it displaces one would naturally expect the conductivity of the 

 silver nitrate to increase on the addition of the hydrochloric acid. 

 From the observation described above it seemed evident, however, 

 that the conductivity under the circumstances stated, did not follow 

 the ordinary laws of electrolj'sis, and in order to examine the effect 

 more fully a series of experiments was made under a variety of con- 

 ditions described below. 



Description oj the apparatus. — The resistance of the solution was 

 measured by a method similar to that adopted by G. B. Bryan^ in 

 "The Conductivity of Liquids in Thin Layers." The arrangement is 

 shewn in Fig. 1. 



By means of the double commutator CC an alternating current 



was supplied to two corners of a Wheatstone Bridge, and since the 



connections to the galvanometer were reversed at the same time as 



' the current, any current through the galvanometer was always in one 



direction. The commutator had two ebonite drums, each with two 



1 Phil. Mag., Nov. 1906, p. 472. 



2 Bryan, Phil. Mag. 45, pp. 253-270, 1906. 



