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Cathodic and anodic polarization curves of zirconium in neutral sodium chloride solution were determined at constant current densities between 3.5 X 10 -s and 3.5 X 10-3 amp/cm ~.In aerated 0.5M NaC1, the cathode reaction occurring below the oxygen limiting diffusion current of 2 X 10 -4 amp/cm 2 was reduction of 02 to OH-. At current densities above the diffusion wave, hydrogen was evolved. Change in salt concentration resulted in a slight shift of diffusion current due to change in oxygen solubility. In deaerated 0.5M chloride solution, the oxygen diffusion current decreased with decrease in oxygen concentration. The slope of the Tafel line obtained is 0.12, and the hydrogen overvoltage for this system is 0.83 volt at 1 ma/cmL Another wave occurred at 2 X 10 -6 amp/cm 2 and is explained as the reduction of a surface oxide layer on the metal.Anodically, zirconium dissolved in 0.5M NaC1. The dissolution potential, 0.15 volt, did not vary with current density. Commercial zirconium and pure hafnium also dissolved under similar conditions.In neutral sulfate solutions, zirconium was passive under anodic treatment. At current densities above 1 X 10 -3 amp/cm 2 the potential reached an apparently constant value in about ten minutes. After a period depending on current density, this was followed by a sudden increase in potential to 28.5 volts. This potential is a result of an IR drop across a surface layer of oxide.

Ethylene glycol is seen to be the most selective solvent at the temperature studied. It also is the only solvent of the three that will permit recovery of both components pure. Its low solubility characteristics, however, require high solvent to feed ratios.Experimental data collected for each of the three solvents studied are tabulated in Tables II and III. LITERATURE CITED (1)