INDUSTRIAL ELECTRO-CHEMISTRY 147 



soda and chlorine from our cell we would have a new electro- 

 chemical system. The catholj^te would then be a mixture 

 of caustic soda and sodium chloride and the ions of caustic 

 soda would participate in the conduction of the current and 

 hydroxyl ions would travel towards the anode and produce 

 new reactions. New reactions of a secondary nature would 

 also be started by the mixing of the chlorine and caustic in the 

 solution, due to diffusion and convection currents. It is thus 

 clear that since our electrochemical system has changed we 

 get new products which we do not want. The technical 

 problem is, therefore, to keep the anodic and cathodic products 

 of electrolysis separate from each other. It has been solved 

 in three essentially different ways. 



The first is to separate both compartments mechanically 

 by a diaphragm. As an early pioneer of diaphragm processes, 

 E. A. Le Sueur has been active in this country. The largest 

 American plant using a diaphragm process (that of the Dow 

 Chemical company) is situated in Midland, Mich., while 

 various diaphragm processes are in successful use in numerous 

 paper and pulp mills, notably in New England. 



The second general method is to keep the anodic and 

 cathodic liquids separate from each other by making use of 

 their different specific gravities (Glockenprocess, gravity proc- 

 ess). This method is specially interesting as one of the com- 

 paratively few cases in which scientific research (in this case 

 the determination of the transport numbers of the ions) has 

 finally led to a new industrial process. While this process 

 is in successful operation abroad, it has not yet been intro- 

 duced into this country. 



The third general method is to ehminate the sodium ions 

 which are discharged at the cathode by alloying them with the 

 mercury cathode. This process in the form developed by 

 Hamilton Young Castner and C. Kellner is in use on a large 

 scale in Niagara Falls. The ehmination of the sodium from 

 the cell by alloying it with a fused lead cathode in the Acker 

 process is, of course, quite analogous. 



In the manufacture of caustic soda and bleaching powder 

 by electrolysis of sodium chloride, the electrolytic methods, 

 sketched above, had to compete with one of the most firmly 



