Sodium metasilicate is the chemical substance with formula Na2SiO3, 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.
Contents
1 Preparation and properties
2 Structure
3 See also
4 References
Preparation and properties
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]
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.
See also
Potassium metasilicate
Sodium orthosilicate
Sodium pyrosilicate