Sodium hypophosphite Hypophosphorous acid Calcium Hypophosphite Tetrakis(Hydroxymethyl) Phosphonium Sulfate Tetrakis(hydroxymethyl) phosphonium chloride Tetrakis(hydroxymethyl) phosphonium chloride-urea (THPC-UREA) Tetrakis(Hydroxymethyl) Phosphonium Sulfate --urea (THPC-UREA) Benzene sulfonyl chloride