The selectivity and yield (based on phosphorus) of sodium phosphite pr
oduction by the interaction of 60-70% phosphorus slime with a concentr
ated NaOH solution have been studied as functions of the P:NaOH and P:
H2O ratios in the reaction mixture, the order of adding reagents (alka
li solution to a slime suspension or vice versa), and the stirring rat
e. The concentrations of sodium phosphite and hypophosphite and of pho
sphates in the liquid phase have been analyzed. Kinetic curves of phos
phite and hypophosphite formation for various values of the parameters
are presented. The possible contribution of various reactions to the
process and their influence on the process selectivity are analyzed.