GB936890A - Process for the production of hypophosphites - Google Patents

Abstract

Alkali metal or alkaline earth metal hypophosphites are produced by reacting white phosphorus in at least 5% excess of that stoichiometrically required with aqueous solutions or suspensions of alkali metal or alkaline earth metal hydroxides containing more than 30% by weight of the metal hydroxide at a temperature of 20 DEG to 44 DEG C., the phosphorus being used in the form of finely divided particles having a surface area of at least 1 m.2/g. and a thickness of at most 0,5 mm. After reduction in the development of the phosphine also produced by the reaction the reaction mixture may be heated, preferably for a short time, at temperatures above the melting point of the phosphorus, e.g. between 44 DEG and 65 DEG C. The finely divided phosphorus is preferably used in the form of a sludge or an p aqueous suspension having a solids content of more than 10%. The sludge may be obtained by quenching gases containing a relatively small amount of phosphorus, e.g. phosphorus furnace gases, with cold water. The starting gases preferably contain 0,03 to 3% by weight phosphorus vapour, 5 to 98% by volume water vapour, and less than 5% of air, the oxygen to phosphorus ratio lying between 0,01 and 1. The hydroxide used is preferably a sodium, potassium, calcium or barium hydroxide and the reaction desirably takes place in an inert gas atmosphere, e.g. nitrogen or argon.