PROCESS FOR PRODUCING AQUEOUS ALKALI METAL PHOSPHATE SOLUTIONS

1. Process for making aqueous alkali metal phosphate solutions by subjecting aqueous alkali metal phosphite solutions to catalytic oxidation with oxygen or air, wherein oxygen or air in stoichiometric excess is introduced into the aqueous alkali metal phosphite solution or into an aqueous solution of alkali metal phosphites and alkali metal phosphates having a temperature of about 30 to 110 degrees C and a pH-value of 0 to 8, in the presence of SiO2 or aluminosilicate containing at most 10 weight % of Al2 O3 , the SiO2 or alumino-silicate having optionally finely divided palladium applied thereto, for as long as necessary to achieve maximum conversion of the alkali metal phosphite to alkali metal phosphate and, after completion of the oxidation, the aqueous solution is separated from the catalyst.