ELECTROLYSIS 195 



to the deposition of metals there is also the liberation of hydrogen, 

 now required on a very large scale, by electrolysis of alkaline 

 solutions. The liquid round the anode in any electrolytic 

 arrangement is exposed to oxidising influence, while the cathode 

 provides a means of reduction, and both these effects are now 

 turned to account for manufacturing a considerable number of 

 salts and other compounds formerly procured by purely chemical 

 processes. Falling water is usually the source of the energy 

 which is transmuted through the current into chemical energy 

 and heat in the cells, and at Niagara, for example, there has 

 been a large development of electrical industries on both the 

 Canadian and American sides. 



Potassium chlorate is an important compound formerly made 

 by passing chlorine gas into alkaline solutions. It is now made 

 almost exclusively by the electrolysis of potassium chloride 

 solution, keeping the liquid at about 70 C., at which temperature 

 the hypochlorite formed at lower temperature is changed into a 

 mixture of chlorate and chloride. When the electrolytic cell is 

 divided by a diaphragm so that the electrodes are kept separate 

 the electrolysis of sodium chloride may be arranged to yield 

 caustic soda and hydrogen gas at the cathode, with chlorine at 

 the anode. The gases may be led off and utilised in any way 

 desired. The caustic soda is in the solution, and when the 

 decomposition is effected in the Castner cell it is obtained free 

 from common salt. 



Another important product is permanganate, which was 

 formerly prepared by fusing together black oxide of manganese 

 and potassium hydroxide or carbonate, whereby a green 

 manganate, K 2 Mn0 4 , is formed. By passing carbon dioxide 

 through the solution one-third of the manganese was pre- 

 cipitated as dioxide Mn0 2 , while the potassium carbonate and 

 permanganate were left in solution. In order to prevent waste 

 of potash the manganate may be dissolved from the fused mass 

 by water, and submitted to electrolysis with iron electrodes at a 

 temperature of about 60, when the manganate is oxidised to per- 

 manganate. Other salts, such as perchlorates and persulphates, 

 are obtained in a similar manner. 



On the other hand, the electrolytic method is applied to 

 reduction, and a good example is afforded by the preparation of 

 hydroxylamine from nitric acid. The electrolyte is sulphuric 

 acid of 40 per cent strength, to which nitric acid is slowly added 



