The process of the thermal decomposition of lead cyclo-tetraphosphate dihydrate (P4m), Pb2P4O12·2H2O, was investigated using X-ray analysis, DTA-TG, HPLC, Isotachophoresis (IP), and IR spectrometry. P4m lost water of crystallization at about 100 °C. In the region of 150–170 °C, P4m decomposed to form oligo phosphates, and at about 190 °C, oligo phosphates changed to a crystalline material which contained ortho- and triphosphate. At about 300 °C, the crystalline material changed to cyclo-octaphosphate (P8m) through a new type of cyclo-tetraphosphate (P4m*). However, in the presence of a higher water-vapor pressure than the atmospheric one, the crystalline material changed mainly to the new type of P4m* with a little P8m, while at a low water-vapor pressure, the reverse tendency was observed: mainly P8m and a little P4m*.
No takes yet. Share an insight, caveat, or question.
Nariai et al. (1987) studied this question.