ACTION OF SULFUR-DIOXIDE ON PHOSPHOCALCIC HYDROXYAPATITE AT DIFFERENTTEMPERATURES

Depending on temperature and heating time, the reaction between sulfur dioxide and phosphocalcic hydroxyapatite Ca10(PO4)6(OH)2 gives, eithe r a mixture of calcium sulfate and beta-calcium pyrophoshate (beta-Ca2 P2O7), or a mixture of calcium sulfate and a compound of beta-tricalci um phosphate structure with the formula Ca21-x(PO4)14-2x(SO4)2x with 0 less-than-or-equal-to x less-than-or-equal-to 1, already mentioned in a previous paper. The limiting compound Ca20(PO4)12(SO4)2 called calc ium phosphosufate (CPS), corresponding to x = 1, is obtained with appr opriate conditions of heating temperature, heating time, flow of sulfu r dioxide, which are specified.