Sodium metasilicate

Sodium metasilicate

Names
IUPAC name Sodium metasilicate
Identifiers
CAS Number	6834-92-0 Y pentahydrate: 10213-79-3 nonahydrate: 13517-24-3 Y
3D model (JSmol)	Interactive image
Abbreviations	E550
ChEBI	CHEBI:60720 Y
ChemSpider	21758 Y
ECHA InfoCard	100.027.193
EC Number	600-279-4229-912-9
MeSH	Sodium+metasilicate
PubChem CID	23266 pentahydrate: 61495 nonahydrate: 61639
RTECS number	VV9275000
UNII	052612U92L Y nonahydrate: D8D44215LZ Y
UN number	1759 3253
CompTox Dashboard (EPA)	DTXSID7029669
InChI InChI=1S/2Na.O3Si/c;;1-4(2)3/q2*+1;-2 Y Key: NTHWMYGWWRZVTN-UHFFFAOYSA-N Y InChI=1/2Na.O3Si/c;;1-4(2)3/q2*+1;-2 Key: NTHWMYGWWRZVTN-UHFFFAOYAB
SMILES [Na+].[Na+].[O-][Si]([O-])=O
Properties
Chemical formula	Na2SiO3
Molar mass	122.062 g·mol−1
Appearance	White crystals
Density	2.61 g/cm3
Melting point	1,088 °C (1,990 °F; 1,361 K)
Solubility in water	22.2 g/100 ml (25 °C) 160.6 g/100 ml (80 °C)
Solubility	insoluble in alcohol
Refractive index (nD)	1.52
Thermochemistry
Heat capacity (C)	111.8 J/(K·mol)
Std molar entropy (S⦵298)	113.71 J/(K·mol)
Std enthalpy of formation (ΔfH⦵298)	−1561.43 kJ/mol
Gibbs free energy (ΔfG⦵)	−1427 kJ/mol
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H302, H314, H315, H319, H335
Precautionary statements	P260, P261, P264, P270, P271, P280, P301+P312, P301+P330+P331, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P310, P312, P321, P330, P332+P313, P337+P313, P362, P363, P403+P233, P405, P501
NFPA 704 (fire diamond)	2 0 0
Lethal dose or concentration (LD, LC):
LD50 (median dose)	1153[clarification needed] (rat, oral)
Safety data sheet (SDS)	Avantor Performance Materials
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

Sodium metasilicate is the chemical substance with formula Na
₂SiO
₃, which is the main component of commercial sodium silicate solutions. It is an ionic compound consisting of sodium cations Na⁺
and the polymeric metasilicate anions [–SiO²⁻
₃–]_n. It is a colorless crystalline hygroscopic and deliquescent solid, soluble in water (giving an alkaline solution) but not in alcohols.^[1]

The anhydrous compound can be prepared by fusing silicon dioxide SiO
₂ (silica, quartz) with sodium oxide Na
₂O in 1:1 molar ratio.^[2]

The compound crystallizes from solution as various hydrates, such as

• pentahydrate Na
  ₂SiO
  ₃·5H
  ₂O (CAS 10213-79-3, EC 229-912-9, PubChem 57652358)
• nonahydrate Na
  ₂SiO
  ₃·9H
  ₂O (CAS 13517-24-3, EC 229-912-9, PubChem 57654617)^[3]

In the anhydrous solid, the metasilicate anion is actually polymeric, consisting of corner-shared {SiO₄} tetrahedra, and not a discrete SiO₃²⁻ ion.^[4]

In addition to the anhydrous form, there are hydrates with the formula Na₂SiO₃·nH₂O (where n = 5, 6, 8, 9), which contain the discrete, approximately tetrahedral anion SiO₂(OH)₂²⁻ with water of hydration. For example, the commercially available sodium silicate pentahydrate Na₂SiO₃·5H₂O is formulated as Na₂SiO₂(OH)₂·4H₂O, and the nonahydrate Na₂SiO₃·9H₂O is formulated as Na₂SiO₂(OH)₂·8H₂O.^[5] The pentahydrate and nonahydrate forms have their own CAS Numbers, 10213-79-3 and 13517-24-3 respectively.

Sodium metasilicate reacts with acids to produce silica gel.^[6]

• Cements and Binders - dehydrated sodium metasilicate forms cement or binding agent.
• Pulp and Par - sizing agent and buffer/stabilizing agent when mixed with hydrogen peroxide.
• Soaps and Detergents - as an emulsifying and suspension agent.
• Automotive applications - decommissioning of old engines (CARS program), cooling system sealant, exhaust repair.
• Egg Preservative - seals eggs increasing shelf life.
• Crafts - forms "stalagmites" by reacting with and precipitating metal ions. Also used as a glue called "soluble glass".
• Hair coloring kits

• Potassium metasilicate
• Sodium orthosilicate
• Sodium pyrosilicate