Abstract
Conditions for dehydration of HIO3 and formation of HIO3, HI3O8 and I2O5 were examined through TGA, DTA and X-ray analysis. HIO3 showed two dehydration processes at 90140°C (HIO3→HI3O8) and 200230°C (HI3O8→I2O5), and the quantitative ratio of the dehydration was found to be 2 : 1. The stable region of each component was observed at less than 80°C in the case of HIO3, 100190°C in the case of HI3O8 and more than 230°C in the case of I2O5. At any temperature between any two of the above mentioned degrees, the mixed components of the two were obtained. HIO3 is obtainable, by crystallizing or drying, at less than 70°C, while HI3O8 is prepared if HIO3 is either dehydrated by heating at 120150°C or evaporated to be crystallized directly from the solution at a higher temperature. Otherwise, it is obtainable if I2O5 absorbs water. However, the DTA curves of HI3O8 thus obtained are a little different from each other, and it is presumed to be caused by the structural irregularity. I2O5 is obtained by dehydration at a higher temperature than 230°C.
