Phosphorous acid (H₃PO₃)：CAS No. 13598-36-2, EINECS :237-066-7

White crystal. Easily soluble in water, ethyl alcohol, has a strong reducing property oxidized to orthophosphoric acid slowly in the air. It is mainly used as raw materials for manufacturing plastic stabilizer, for the production of high-efficiency water treatment agent, organophosphorus pesticide, nylon whitening agent, and also for the manufacture of synthetic fibers and phosphites.