Process for the production of alkali metal hypophosphites

A process for the continuous production of an alkali metal hypophosphite which comprises:

• (a) continuously feeding an aqueous solution of an alkali metal hydroxide having a concentration of at least 10 wt. % and white phosphorus to a reactor having an inert gas atmosphere and maintained at a temperature higher than the melting point of white phosphorus, stirring and dispersing the white phosphorus while introducing an inert gas thereinto, carrying out the reaction under conditions such that molten white phosphorus is always present in the reactor, continuously withdrawing the reaction mixture containing alkali metal hypophosphite and alkali metal phosphite with an alkali metal hypophosphite/(alkali metal hypophosphite+alkali metal phosphite) component ratio by weight of at least 0.2, from the reactor and then feeding said reaction mixture to a separator connected with the reactor,
• (b) settling the reaction mixture in the separator in an inert gas atmosphere and maintained at a temperature of higher than the melting point of white phosphorus, thereby precipitating and separating the white phosphorus from the crude solution of the alkali metal hypophosphite, withdrawing the white phosphorus from the bottom of the separator, recycling to the reactor, continuously feeding the crude solution of the alkali metal hypophosphite to an electrodialytic cell, in which cation exchange membranes and univalent anion permselective membranes are alternatively arranged between a cathode compartment and an anode compartment to form at least one pair of a desalting compartment and a concentrating compartment, subjecting the crude solution to electrodialysis until the component ratio is at least 0.9 in the concentrating compartment and obtaining a purified solution of the alkali metal hypophosphite.