Sodium hypochlorite is a chemical compound with the formula NaOCl or NaClO, comprising a sodium cation (Na+) and a hypochlorite anion (OCl−or ClO−). It may also be viewed as the sodium salt of hypochlorous acid. The anhydrous compound is unstable and may decompose explosively. It can be crystallized as a pentahydrate NaOCl•5H2O, a pale greenish-yellow solid which is not explosive and is stable if kept refrigerated.