BaCO₃とGeO₂の反応

抄録

The reaction between BaCO₃ and GeO₂ has been studied in air and in CO₂ at 800-1000°C. Several products (Ba₂GeO ₄, BaGeO ₃ and BaGe₄O₉) were obtained when the mixtures of BaCO₃ and GeO₂ were heated in air, but under the CO₂ atmosphere of 393-763mmHg, Ba₂GeO ₄ was prepared with very small amounts of BaGeO₃ and BaGe₄O₉ so far as BaCO₃ was remaining in the samples.
The kinetics of the following reaction were studied under the CO₂ atmosphere of 763 mmHg.
2BaCO₃+GeO₂=Ba₂GeO₄+2CO₂
The kinetic data can be expressed reasonably by the zero-order equation. There is a discontinuity in the plotting of log k against 1/T at about 830°C or 840°C for the reaction of BaCO₃ with hexagonal GeO₂, or with tetragonal GeO₂, respectively. The values of activation energy are about 37 or 16 kcal/mol above or below 830°C, respectively, for the reaction of BaCO₃ with hexagonal GeO₂, and 65 or 22 kcal/mol above or below 840°C, respectively, for the reaction with tetragonal GeO₂. The kinetic data are discussed in comparison with the kinetic dada for the reaction between BaCO₃ and TiO₂ under the atmosphere of CO₂.