Thermal decomposition of potassium silicotungstate in air and in hydrogen flow

With the aid differential-thermal and X-ray phase analysis as well as of the complex metnod of stepwise annealing and ''hydration'' it has been established that upon heating potassium silicotungstate in air up to 900 deg C the decomposition process is described by the following equation K4[SiW12O40]→2K2W6O19+SiO2. Upon heating in a hydrogen flow the decomposition of potassium tungstate gives rise to the formation of metal tungstate and is described by the equation: 2K4[SiW12O40 H2]yields 3K2WO4+K2Si2O5+21W+31.5H2O