Sodium thiosulphate is an inorganic compound with the formula Na₂S₂O₃xH₂O. Typically it is available as the white or colorless pentahydrate, Na₂S₂O₃·5H₂O. The solid is an efflorescent crystalline substance that dissolves well in water. It is also often called sodium hyposulphite or hypo.
Formula: Na2S2O3