Sodium Hydroxide → Phosphoric Acid

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Reaction Steps

Sodium hypophosphite is prepared by reacting tetraphosphorus, P4, with an aqueous solution of sodium hydroxide. This reaction produces a solution of about 50 wt % sodium hypophosphite, about 25 wt % sodium phosphite, and about 25 wt % of a gaseous mixture of phosphine and hydrogen in a 1:1 molar ratio. (Other alkali metal or alkaline earth metal hypophosphites can be made in the same manner.) At the present time, the practice is to burn the phosphine-hydrogen mixture in air followed by scrubbing in water to produce phosphoric acid. However, the resulting phosphoric acid has about the same value as the P4 starting material, so no value is added by these additional steps.

Provenance & Evidence