Controlled Potential Coulometry of Metals in Fused Lithium Chloride-Potassium Chloride Eutectic

The controlled potential coulometric determination of platinum, copper, chromium, and vanadium in fused lithium chloride-potassium chloride eutectic was studied. Platinum(II) was determined with a relative error of 0.67% by plating out the metal, and copper(II) with a relative error of 0.45% both by deposition of the metal and by stripping from graphite or platinum electrodes. Chromium was determined with a relative error of 0.38%, by reduction of chromium(III) to chromium(II), and vanadium wit a relative error of 1.0% by oxidation of vanadium(III). sing a coulometric procedure, the standard electrode potentials of the vanadium(III) -- vanadium(II) and chromium(III) chromium(II) systems were determined in solutions ranging from 0.016 to 0.04M. Polarograms of niobium solutions made by anodizing the metal in the melt exhibited two waves. Coulometric and polarographic data indicated that the solutions contained niobium(IV) and niobium(III) in a concentration ratio of 3 to 1.