Sodium stannate

Sodium stannate, formally sodium hexahydroxostannate(IV), is the inorganic compound with the formula Na₂[Sn(OH)₆]. This colourless salt forms upon dissolving metallic tin or tin(IV) oxide in sodium hydroxide and is used as a stabiliser for hydrogen peroxide.^[2] In older literature, stannates are sometimes represented as having the simple oxyanion SnO₃²⁻,^[3] in which case this compound is sometimes named as sodium stannate–3–water and represented as Na₂SnO₃·3H₂O, a hydrate with three waters of crystallisation.^[1] The anhydrous form of sodium stannate, Na₂SnO₃, is recognised as a distinct compound with its own CAS Registry Number,^[4] 12058-66-1 , and a distinct material safety data sheet.^[5]

Sodium stannate

Names
IUPAC name Sodium hexahydroxostannate(IV)
Other names disodium hexahydroxyltin Sodium stannate(IV) sodium stannate–3–water sodium tin(IV) oxide hydrate
Identifiers
CAS Number	12027-70-2
3D model (JSmol)	Interactive image
ChemSpider	145444 Y
ECHA InfoCard	100.031.554
EC Number	234-724-5
PubChem CID	131868867
UNII	NJ7C1V83KG
CompTox Dashboard (EPA)	DTXSID70891881
InChI InChI=1S/2Na.6H2O.Sn/h;;6*1H2;/q2*+1;;;;;;;+4/p-6 Key: PMPBLIIMRRPPEO-UHFFFAOYSA-H
SMILES [OH-].[OH-].[OH-].[OH-].[OH-].[OH-].[Na+].[Na+].[Sn+4]
Properties
Chemical formula	H6Na2O6Sn
Molar mass	266.73 g/mol
Appearance	Colorless or white solid
Density	4.68 g/cm3
Boiling point	N/A
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H314, H315, H319, H335, H412
Precautionary statements	P260, P261, P264, P271, P273, P280, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P310, P312, P321, P332+P313, P337+P313, P362, P363, P403+P233, P405, P501
NFPA 704 (fire diamond)	2 0 0
Flash point	57 °C (135 °F; 330 K)
Autoignition temperature	N/A
Lethal dose or concentration (LD, LC):
LD50 (median dose)	2132 mg/kg [Mouse]
Safety data sheet (SDS)	[1][1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Alkali metal stannate compounds are prepared by dissolving elemental tin in a suitable metal hydroxide, in the case of sodium stannate by the reaction:^[6]

Sn   +   2 NaOH   +   4 H₂O   →   Na₂[Sn(OH)₆]   +   2 H₂

A similar reaction occurs when tin dioxide is dissolved in base:

SnO₂   +   2 NaOH   +   2 H₂O   →   Na₂[Sn(OH)₆]

The anhydrous form can also be prepared from tin dioxide by roasting with sodium carbonate in a mixed carbon monoxide / carbon dioxide environment:^[7]

SnO₂   +   Na₂CO₃   →   Na₂SnO₃   +   CO₂

The anion is a coordination complex that is octahedral in shape, similar to most stannates, such as the hexachlorostannate anion [SnCl₆]²⁻. The Sn—O bond distances average 2.071 Å.^[8]