Sodium metasilicate
Sodium metasilicate is the chemical substance with formula Template:Chem, which is the main component of commercial sodium silicate solutions. It is an ionic compound consisting of sodium cations Template:Chem and the polymeric metasilicate anions [–Template:Chem–]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 (silica, quartz) with sodium oxide Template:Chem in 1:1 molar ratio.[2]
The compound crystallizes from solution as various hydrates, such as
- pentahydrate Template:Chem·5Template:Chem (CAS 10213-79-3, EC 229-912-9, PubChem 57652358)
- nonahydrate Template:Chem·9Template:Chem (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
- ↑ Chemical Book: "Sodium metasilicate". Accessed on 2018-05-13.
- ↑ J. F. Schairer and N. L. Bowen (1956): "The system Template:Chem—Template:Chem—Template:Chem". American Journal of Science, volume 254, issue 3, pages 129-195 Script error: No such module "doi".
- ↑ 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 "doi".
- ↑ Template:Greenwood&Earnshaw
- ↑ Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications Template:ISBN
- ↑ Script error: No such module "citation/CS1".