The thermal behaviour of H4SiW12O4024.8H2O (SiW12) was investigated by using DTA, TG and FTIR. Endothermic effects were observed at 40, 98 and 217C, corresponding to the
fusion of SiW12 in its own crystallization water, boiling of the solution and decomposition of the remaining tetrahydrate into anhydrous
SiW12, respectively. The mass of the sample remained constant on heating from about 250 to 400C. Subsequently, it slowly decreased
and reached a constant value at about 500C. At 526C a DTA peak appeared. There was an abrupt change in the FTIR spectrum
of the sample heated to 550C. The typical spectrum of the Keggin unit vanished and new bands at 807.5 and 1030 cm−1 indicated the presence of free WO3 and SiO2, respectively.