CONTROLLED POTENTIAL COULOMETRIC AND POLAROGRAPHIC INVESTIGATIONS OF METALLIC IONS IN FUSED SALTS
Two types of platinum(II)--platinum(O) reference electrodes used in fused lithium chloride-potassium chloride eutectic were compared and tested with respect to their stability with repeated use. One type was completely enclosed in a borosilicate glass tube, the glass serving as a salt bridge to the melt, whereas the other contained a small asbestos fiber sealed into the end of the glass tube. Both electrodes were found to be stable over long periods of time and capable of withstanding intermittent use for more than a year. Small drifts were noted, but such deviations were not significant when the electrodes were used for reference during controlled potential coulometric analyses which were performed in the melt. The controlled potential coulometric analysis of platinum, copper, chromium, and vanadium in fused lithium chloride--potassium chloride was studied. Platinum(II) analyses were performed with an average error of plus or minus 0.67 percent by plating out the metal on a platinum working electrode. Analyses of copper(I) solutions were performed with an average error of plus or minus 0.45 percent both by deposition of the metal and by stripping from a graphite or platinum electrode at controlled potential. Use of cylindrical electrodes with inert gas bubbling through the center of the cylinder provided efficient stirring and allowed electrolyses to be completed in four to five minutes. Chromium was determined with an average error of plus or minus 0.38 percent by reduction of chromium (III) to chromium(II) at a graphite electrode. Vanadium was determined by oxidation of vanadium(II) to vanadium (III) with an average error of plus or minus 1.0 percent. The presence of oxide ion contamination was found to seriously affect the vanadium determination due to deposition of vanadium (III) oxide at more negative potentials. Using a precise 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 M to 0.04 M. The electrochemical behavior of niobium solutions in the lithium chloride-potassium chloride eutectic was studied by anodizing the metal in the melt and recording polarograms taken at a platinum' microelectrode. Polarograms of solutions made by anodizing the metal exhibited two waves, the first of which was a composite wave involving a one- electron reduction step. Coulometric data obtained during the anodization of the metal and the relative heights of the anodic and cathodic portions of the composite wave indicated the presence of niobium(IV) and niobium(III) in the approximate concentration ratio of 3:1. The second wave appeared to be a two- or three-electron deposition process which was not clearly defined. The diffusion current of the first wave was found to be proportional to the amount of niobium dissolved in the melt. Polarographic studies of a series of metal oxides dissolved in fused alkali metaphosphates demonstrated the formation of several stable species which exhibited diffusion controlled current-voltage curves. Uranium(VI), copper(II), iron(III), and vanadium(IV) produced reduction waves involving two electrons for the uranium and one electron for the other metals. Sulfate ion was found to undergo a two-step reduction to sulfite ion and sulfide ion. Silver was the only metal found to deposit over the concentration ranges studied. (Dissertation Abstr., XXIII, No. 12(I))
- Research Organization:
- Originating Research Org. not identified
- NSA Number:
- NSA-17-030555
- OSTI ID:
- 4676306
- Resource Relation:
- Other Information: Thesis. Orig. Receipt Date: 31-DEC-63
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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Related Subjects
ALKALI METALS
ANODES
ASBESTOS
BORON SILICATES
CHROMIUM COMPOUNDS
COPPER COMPOUNDS
CURRENTS
DIAGRAMS
DIFFUSION
ELECTRIC POTENTIAL
ELECTROCHEMISTRY
ELECTRODES
ELECTRONS
ERRORS
EUTECTICS
FUSED SALTS
GLASS
GRAPHITE
INERT GASES
IRON COMPOUNDS
LITHIUM CHLORIDES
METALS
MIXING
NIOBIUM COMPOUNDS
OXIDES
PHOSPHATES
PLATING
PLATINUM
POLAROGRAPHY
POTASSIUM CHLORIDES
QUALITATIVE ANALYSIS
QUANTITATIVE ANALYSIS
REDUCTION
RESIDUES
SEALS
SILVER
SOLUTIONS
STABILITY
SULFATES
SULFIDES
TUBES
URANIUM COMPOUNDS
VANADIUM COMPOUNDS