Graphite oxidation in sodium carbonate/sodium sulfate melts

Article abstract of DOI:10.1021/ic00131a021

The oxidation of spectroscopic grade graphite in sodium carbonate/sodium sulfate melts using oxidizing (air and oxygen) or inert (argon and nitrogen) sparge was investigated between 900 and 1000°C. The oxidation rate increased with increasing graphite surface area, increasing melt temperature, and increasing oxygen concentration. The rate, in oxidizing atmospheres, at 900°C was faster in pure sodium carbonate than in pure sodium sulfate with the maximum rate observed in mixed melts. At 950°C the oxidation rate was virtually equal in the two pure melts, and at 982°C the rate was faster in pure sodium sulfate. In melts containing sodium sulfate, the rate-determining step was apparently the same for reactions conducted in oxidizing and inert atmospheres, with sodium sulfate acting as a catalyst in the former and a reagent in the latter. Sequences of reactions are proposed for the oxidation of graphite in pure sodium carbonate, pure sodium sulfate, and mixed melts.