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The oxidation of carbon by cuprous oxide-lead oxide-silica melts Joshi, Ashok Purushottam


An investigation of the relationship between the kinetics of the oxidation of spectroscopic grade graphite with the oxidising potential of cuprous oxide-lead oxide-silica melts was undertaken. The kinetics of the reaction were studied at two temperatures over a wide range of oxidising potentials. In all cases it was observed that the rate of oxidation was proportional to the equilibrium oxygen pressure of the system and the square of the activity of the oxygen ions. The variation of the rate constant with temperature indicated that O⁻⁻ are involved in the rate determining step. At a given temperature the rate constants for the simple PbO—SiO₂ and the complex Cu₂O—PbO—SiO₂ slags were found to be of the same order of magnitude, if O⁻⁻ were considered. Hence the rate expression could be written as [formula omitted] The activation energy of oxidation of graphite was determined over a wide range of PbO—SiO₂ composition, and found to have a value of 22±2 Kcal./mole. The activation energy for spectroscopic grade carbon was found to have a value of 22 Kcal./mole, indicating that the activation energy was independent of the nature of the carbon surface. The constant A was observed to have a value of 12 for the slags investigated. The theory of the ionic equilibrium in silicate melts devised by Toop and Samis was extended to calculate aO⁻⁻ and silica in multicomponent silicate slags. The present investigation appears to substantiate their theory. The results obtained in this study indicate that aO⁻⁻ in an unknown silicate melt might be determined by oxidising carbon in the melt and measuring the rate of oxidation.

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