Sodium metasilicate
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Template:Chembox image cellTemplate:Chembox image cellTemplate:Chembox image cellTemplate:Chembox AllOtherNamesTemplate:Chembox headerbarTemplate:Chembox IndexlistTemplate:Chembox JmolTemplate:Chembox ChEMBLTemplate:Chembox ECHATemplate:Chembox E numberTemplate:Chembox IUPHAR ligandTemplate:Chembox UNIITemplate:Chembox CompToxTemplate:Chembox headerbarTemplate:Chembox SolubilityInWaterTemplate:Chembox headerbarTemplate:Chembox DeltaGfreeTemplate:Chembox headerbarTemplate:Chembox GHS (set)Template:Chembox Lethal amounts (set)Template:Chembox SDSTemplate:Chembox Datapage checkTemplate:Chembox Footer| Template:Longitem | Template:Unbulleted list |
| Abbreviations | E550 |
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| KEGG | Template:Unbulleted list |
| MeSH | Sodium+metasilicate |
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| RTECS number | Template:Unbulleted list |
| UN number | 1759 3253 |
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| Template:Longitem | Na2SiO3 |
| Molar mass | Template:Chem molar mass |
| Appearance | White crystals |
| Density | 2.61 g/cm3 |
| Melting point | Template:Chembox CalcTemperatures |
| Solubility | insoluble in alcohol |
| Template:Longitem | 1.52 |
| Template:Longitem | 111.8 J/(K·mol) |
| Template:Longitem | 113.71 J/(K·mol) |
| Template:Longitem | −1561.43 kJ/mol |
| NFPA 704 (fire diamond) | Template:NFPA 704 diamond |
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Sodium metasilicate is the chemical substance with formula Template:Chem/link, which is the main component of commercial sodium silicate solutions. It is an ionic compound consisting of sodium cations Template:Chem/link and the polymeric metasilicate anions [–Template:Chem/link–]n. It is a colorless crystalline hygroscopic and deliquescent solid, soluble in water (giving an alkaline solution) but not in alcohols.[1]
Preparation and properties
The anhydrous compound can be prepared by fusing silicon dioxide Template:Chem/link (silica, quartz) with sodium oxide Template:Chem/link in 1:1 molar ratio.[2]
The compound crystallizes from solution as various hydrates, such as
- pentahydrate Template:Chem/link·5Template:Chem/link (CAS 10213-79-3, EC 229-912-9, PubChem 57652358)
- nonahydrate Template:Chem/link·9Template:Chem/link (CAS 13517-24-3, EC 229-912-9, PubChem 57654617)[3]
Structure
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.
Uses
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
See also
References
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- ↑ Chemical Book: "Sodium metasilicate". Accessed on 2018-05-13.
- ↑ J. F. Schairer and N. L. Bowen (1956): "The system Template:Chem/link—Template:Chem/link—Template:Chem/link". American Journal of Science, volume 254, issue 3, pages 129-195 Script error: No such module "CS1 identifiers".
- ↑ M. F. Bechtold (1955): "Polymerization and Properties of Dilute Aqueous Silicic Acid from Cation Exchange" Journal of Physical Chemistry, volume 59, issue 6, pages 532–541. Script error: No such module "CS1 identifiers".
- ↑ Script error: No such module "citation/CS1".
- ↑ Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications Template:ISBN
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