Thermal and X-ray diffraction investigations of the binary system chromium(III) oxide — barium perchlorate trihydrate

Abstract

Chromium(Ill.) oxide reverses the sequence of dehydration of barium perchlorate trihydrate (BP). Between 223 and 310 ~ the oxide reacts with anhydrous BP in a 1:1 molar ratio to give the yellow barium dichromite BaCr204. Between 350 and 430 ~ this material reacts in 1:1 stoichiometry with BP, to give barium chromate BaCrO 4. The products have been identified by X-ray diffraction analysis. The formation of an unkown phase is also reported.Chromium(l I I) oxide has been shown to catalyse the thermal decomposition of the perchlorates and the chlorates of the alkali metals [1][2][3], and to interact chemically to give the metal dichromates [2,3]. The oxide also catalyses the decomposition of alkali metal pyrosulphates to the sulphates through the formation of chromium sulphate or the double sulphates with the alkali metals [4]. Udupa and Srinivasan [5] recently reported that the oxide reacts with barium chlorate via complex stoichiometry to give barium chromate BaCrO4 and barium chloride. On the other hand, the thermal decomposition of barium perchlorate (BP) is catalysed by manganese(IV)oxide and europium(Ill) oxide and the initial decomposition temperature can be lowered from 460 ~ down to 310 ~ by the action of these oxides [6].It is the purpose of the present work, therefore, to study the effects of Cr203 on the thermal decomposition of barium perchlorate. ExperimentalA MOM-photorecording derivatograph was employed for recording TG, DTG and DTA curves under static air atmosphere; a pair of MOM-platinum crucibles was used for sample and reference material (e-AI203); sample size: 100 mg, heating rate: 10 deg/min. §