The thermal stability of potassium and cesium tetrachlorodioxotungstates

Thermal stability of K2WO2Cl4 and Cs2WO2Cl4 is studied. A weight amount of the initial substance is placed in membrane chamber in such a way that at 600 deg C the total pressure in the system does not exceed 103hPa. It has been established that in the system at the temperature higher 480 deg C besides K2WO2Cl4 transfer into vapour the secondary processes, which are apparently due to the decomposition of the initial compound, take place. As a result of the vapour complex composition, in gaseous phase three compounds can be present simultaneously, therefore, it is impossible to obtain quantitative characteristics of the process using the statistical method. It has been found, that the values of vapour pressure during Cs2WO2Cl4 heating and cooling are in good agreement, which testifies only to the process of transition into gaseous phase of the initial compound Cs2WO2Cl4 at the temperature up to 600 deg C. During reheating the temperature has been increased up to 800 deg C and total pressure reached 898.44hPa. At cooling the pressure values coincide with the ones at heating up 540 deg C. At the next heating the pressure in the membrane chamber increases sharply from 280 deg C, and from 330 deg C the pressure has a linear dependence. At 800 deg C the total vapour pressure reaches 933.1hPa and partial pressure constitutes approximately 66.65hPa or 7% from the total pressure in the membrane