Sodium stannate, formally sodium hexahydroxostannate(IV), is the inorganic compound with the formula Na<sub>2</sub>[Sn(OH)<sub>6</sub>]. This colourless salt forms upon dissolving metallic tin or tin(IV) oxide in sodium hydroxide and is used as a stabiliser for hydrogen peroxide. In older literature, stannates are sometimes represented as having the simple oxyanion SnO<sub>3</sub><sup>2âÂÂ</sup>, in which case this compound is sometimes named as sodium stannate–3–water and represented as Na<sub>2</sub>SnO<sub>3</sub>÷3H<sub>2</sub>O, a hydrate with three waters of crystallisation. The anhydrous form of sodium stannate, Na<sub>2</sub>SnO<sub>3</sub>, is recognised as a distinct compound with its own CAS Registry Number, and a distinct material safety data sheet.
Alkali metal stannate compounds are prepared by dissolving elemental tin in a suitable metal hydroxide, in the case of sodium stannate by the reaction:
A similar reaction occurs when tin dioxide is dissolved in base:
The anhydrous form can also be prepared from tin dioxide by roasting with sodium carbonate in a mixed carbon monoxide / carbon dioxide environment:
The anion is a coordination complex that is octahedral in shape, similar to most stannates, such as the hexachlorostannate anion . The Sn—O bond distances average 2.071 ÃÂ .