ROLE OF SEMICONDUCTIVE OXIDES IN THE THERMAL-DECOMPOSITION OF BARIUM OXALATE

The effect of the semiconductive oxides CuO, TiO2 and Cr2O3 on the isothermal decomposition of barium oxalate has been studied gasometrically. Plots of the fraction decomposed versus time (alpha-t), for pure salt as well as mixtures, indicate an initial gas evolution, a linear period and a sigmoidal regime consisting of acceleratory and decay stages. The data are best fitted to the Prout-Tompkins relationship indicating that nucleation occurs in a chain-branching manner over the entire sigmoidal zone. The oxides CuO and TiO2, being p- and n-type semiconductors respectively, do not affect the initial gas loss or the linear period but facilitate the acceleratory stage. However, the former decelerates the rate of the decay period whereas the latter does not affect it. Cr2O3, a p-type semiconducting oxide retards the rate in both the stages.