Electrolysis, Electroplating, and Electroforming

The electrolyte surrounding the central positive electrode is sodium tet-rachloroaluminate, which melts at 157 °C and acts as a solvent for the nickel(II) chloride, and this is separated from the molten sodium in the outer compartment by a /3-alumina tube which, again, serves as a fast ion conductor for Na . The cell operates at 300 °C and delivers up to 2.58 V. 

Lithium with anode chemistry analogous to reaction 15.94 

Crude hydrogen for industry is most economicedly made today by cracking hydrocarbons (Section 7.3), steam reforming or partial oxidation of methane, or the water-gas reaction (Section 9.3), but if very pure hydrogen and/or oxygen are required, or if electricity is inexpensive, water may 

Other commercially important inorganic chemicals that can be made electrolytically include caustic soda and chlorine, chlorate and perchlorate salts (Chapter 12), potassium dichromate (K2Cr207), manganese dioxide, and potassium permanganate.  

Electrolytic purification of metals is considered at length in Chapter 17. In essence, metals can be deposited in high purity from solution on a cathodic surface, by careful control of the voltage and other parameters. The anode can be a billet of the impure metal, and the impurities will either stay in solution or form an insoluble anode slime here, both dissolution and reprecipitation of the desired metal are accomplished in a single electrolytic step. Alternatively, a crude solution of the meted ion might be prepared by some other means, and the pure metal deposited on a cathode with an anode of some inert material the product of electrolysis at the anode will normally be oxygen gas. 

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