Crystal forms of chromium orthophosphate

There is no evid ence for t h e existence of any crystall ine hydrate of chromium orthophosphate other than the h exahydrate. This breaks down near 130C to an amorphou s material. If Lhe un strain ed and coar se hexahydrate is heated, it recrystallizes at 1,01 4 C to an un stable, fine-grain ed compound (i3CrPO'). If the original hydr ate is ground and thus strained, it will form a stable compound (aCrPO') at 972 C. X-ray diffraction powd er patterns are given for the three crystalline form s, and the general relation of chromium orLhophosphate hexahydrate to other hydrates is discussed .