266 THE ROYAL SOCIETY OF CANADA 



electrical and hydrostatic field. Time, rate of revolution of the 

 cathode, current, and voltage over the cell, were recorded on each 

 of the photographic films. 



Solutions of various concentrations of copper sulphate and of 

 acid were used. The temperature and the rate of revolution of 

 the cathode were varied. The current was continuous, interrupted, 

 abruptly raised or lowered, abruptly alternated, sinusoidal, or sinu- 

 soidal with superposed direct current; and in the case of abrupt 

 change the lengths of the various "beats" were varied. 



In every case the interval before evolution of hydrogen agreed 

 within a few percent with that calculated from the equations deduced 

 by Professors Rosebrugh and Lash Miller in their paper on the 

 mathematical theory of concentration changes at the electrodes ;2 

 the assumptions made in that paper must therefore be regarded as 

 verified by experiment. 



The Electrolysis of Aqueous Sohitions of Sodium Sulphide 



By W. R. Fetzer, M.A. 



Presented by Professor W. Lash Miller, F.R.S.C. 



As a preliminary, the methods of determining the various sulphur 

 acids in solutions containing mixtures of their sodium salts were 

 revised, and new methods introduced. Using these analytical methods 

 it was found that when solutions of sodium polysulphides are electro- 

 lysed in an atmospheie of nitrogen, with rotating platinum anode, 

 and a diaphragm to keep out the cathode solution, the only product 

 at the anode is polysulphide sulphur, exactly 16.00 grams being 

 formed for every faraday of electricity passed through the solution. 

 This holds unless the current density is great enough to cause deposi- 

 tion of free sulphur as a yellow deposit, whereupon sulphate and 

 dithionate of sodium are formed. 



The current density necessary to bring about this deposition of 

 sulphur was then studied as a function of the rate of rotation of the 

 anode and the composition of the electrolyte, and it was found that 

 by dissolving sulphur in a solution of sodium sulphide the current 

 needed to cause deposition of sulphur is first increased, passes through 



^The Journal of Physical Chemistry, vol. 14, p. 816-844 and Trans. Roy. Soc. 

 Can., 1913, Sec. III., p. 210. 



