Studies on the Use of Coulometric and Amperometric Analysis

Citation

Buck, Richard Pierson (1951) Studies on the Use of Coulometric and Amperometric Analysis. Master's thesis, California Institute of Technology. doi:10.7907/QJZB-MY25. https://resolver.caltech.edu/CaltechTHESIS:08092017-100407498

Abstract

A coulometric titration is described in which unipositive thallium is oxidized to the tripositive state by electrolytically generated bromine or chlorine. The end-point is determined amperometrically by measuring the current between two platinum electrodes with an impressed potential difference of 200 millivolts. Confirmatory analyses have shown an accuracy of 0.2% for 93 to 200 microgram samples, and of 0.1% for samples of from 200 to 1900 micrograms.

The application of dual intermediates to secondary coulometric titrations with an amperometric end point has been studied. Cupric copper and bromide have been used for the alternate electrolytic generation of bromine and cuprous copper for the purpose of titrating a substance exhibiting a slow rate of reaction with bromine. A procedure is described by which aniline has been titrated in quantities of from 13 to 280 micrograms with an average error without regard to sign of less than 0.4 micrograms.

A study has been made of the bromine-bromide diffusion current, the effects of the concentrations of bromine, bromide and hydrogen ion; the minimum bromide ion concentration necessary to maintain generation of bromine with 100% current efficiency was determined.

Studies have been made of the diffusion-controlled currents observed when potential differences, less than the decomposition potential, are impressed upon two platinized-platinum electrodes in solutions of hydrochloric acid which are 0.1 VF in potassium chloride and saturated with hydrogen gas. The effects of the electrode size and material, the applied potential, and the presence of oxygen and nitrogen gas are described.

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