A white crystalline solid, H3PO2; r.d. 1.493; m.p. 26.5°C; decomposes above 130°C. It is soluble in water, ethanol, and ethoxyethane. Salts of phosphinic acid may be prepared by boiling white phosphorus with the hydroxides of group I or group II metals. The free acid is made by the oxidation of phosphine with iodine. It is a weak monobasic acid in which it is the –O-H group that is ionized to give the ion H2PO2−. The acid and its salts are readily oxidized to the orthophosphate and consequently are good reducing agents.