Editing Sodium silicate (section)

{{Short description|Hygroscopic chemical compound of variable Na2O/SiO2 ratio precursor of waterglass}}
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'''Sodium silicate''' is a generic name for [[chemical compound]]s with the formula {{chem|Na|2''x''|Si|''y''|O|2''y''+''x''}} or {{chem|(|Na|2|O|)|''x''}}·{{chem|(SiO|2|)|''y''}}, such as [[sodium metasilicate]] ({{chem|Na|2|SiO|3}}), [[sodium orthosilicate]] ({{chem|Na|4|Si|O|4}}), and [[sodium pyrosilicate]] ({{chem|Na|6|Si|2|O|7}}). The anions are often [[polymer]]ic. These compounds are generally colorless transparent solids or white powders, and soluble in water in various amounts.

Sodium silicate is also the technical and common name for a mixture of such compounds, chiefly the metasilicate, also called '''waterglass''', '''water glass''', or '''liquid glass'''. The product has a wide variety of uses, including the formulation of [[cement]]s, coatings, [[passive fire protection]], textile and lumber processing, manufacture of [[refractory]] ceramics, as [[adhesives]], and in the production of [[silica gel]]. The commercial product, available in [[water solution]] or in solid form, is often greenish or blue owing to the presence of iron-containing impurities.

In industry, the various grades of sodium silicate are characterized by their SiO<sub>2</sub>:Na<sub>2</sub>O weight ratio (which can be converted to molar ratio by multiplication with 1.032). The ratio can vary between 1:2 and 3.75:1.<ref name=Ullmann>Gerard Lagaly, Werner Tufar, A. Minihan, A. Lovell "Silicates" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, 2005. {{doi|10.1002/14356007.a23_661}}</ref> Grades with ratio below 2.85:1 are termed alkaline. Those with a higher SiO<sub>2</sub>:Na<sub>2</sub>O ratio are described as neutral.