PROCESS FOR PREPARING MADREL SALT

摘要

1524496 Maddrell sa sodium phosphates HOECHST AG 4 April 1977 [15 April 1976] 14109/77 Heading C1A A process for making Maddrell salt having a purity of more than 95 wt. per cent by heating sodium phosphate to temperatures of 250‹ C. to 420‹ C., comprises: using as the sodium phosphate starting material sodium trimetaphosphate or a mixture of sodium trimetaphosphate with Maddrell salt, monosodium orthophosphate and/or disodium pyrophosphate; admixing the starting material, prior to heating it, with 0À5 to 5 wt. per cent of orthophosphoric acid, polyphosphoric acid, phosphorus pentoxide or one or more salts of a volatile base forming polyphosphoric acid at the temperatures specified; and calcining the resulting mixture over the period necessary to transform the starting material to Maddrell salt.