Sodium metasilicate is the

chemical substance A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., wit ...

with formula , which is the main component of commercial

sodium silicate Sodium silicate is a generic name for chemical compounds with the formula or ·, such as sodium metasilicate , sodium orthosilicate , and sodium pyrosilicate . The anions are often polymeric. These compounds are generally colorless transparent ...

solutions. It is an

ionic compound In chemistry, an ionic compound is a chemical compound composed of ions held together by electrostatic forces termed ionic bonding. The compound is neutral overall, but consists of positively charged ions called cations and negatively charged ...

consisting of

sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...

cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...

s and the

polymer A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...

metasilicate 320 px, Idealized structure of sodium metasilicate. Metasilicates are silicates containing ions of empirical formula . Common stoichiometries include MSiO3 and MIISiO3. Metasilicates can be cyclic, usually the hexamer or chains . Common comp ...

anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...

s ��–sub>''n''. It is a colorless crystalline

hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substance' ...

and

deliquescent Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substance' ...

solid, soluble in water (giving an alkaline solution) but not in alcohols.Chemical Book
"Sodium metasilicate"
Accessed on 2018-05-13.

Preparation and properties

The

anhydrous A substance is anhydrous if it contains no water. Many processes in chemistry can be impeded by the presence of water; therefore, it is important that water-free reagents and techniques are used. In practice, however, it is very difficult to achi ...

compound can be prepared by fusing

silicon dioxide Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is one ...

(silica,

quartz Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical f ...

) with

sodium oxide Sodium oxide is a chemical compound with the formula Na2 O. It is used in ceramics and glasses. It is a white solid but the compound is rarely encountered. Instead "sodium oxide" is used to describe components of various materials such as gla ...

in 1:1 molar ratio.J. F. Schairer and N. L. Bowen (1956): "The system ——". ''American Journal of Science'', volume 254, issue 3, pages 129-195 The compound crystallizes from solution as various

hydrate In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...

s, such as * pentahydrate ·5 (CAS 10213-79-3, EC 229-912-9, PubChem 57652358) * nonahydrate ·9 (CAS 13517-24-3, EC 229-912-9, PubChem 57654617)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.

Structure

In the anhydrous solid, the metasilicate anion is actually polymeric, consisting of corner-shared tetrahedra, and not a discrete SiO₃²⁻ ion. In addition to the anhydrous form, there are hydrates with the formula Na₂SiO₃·''n''H₂O (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. The pentahydrate and nonahydrate forms have their own CAS Numbers
10213-79-3
an
13517-24-3
respectively.

Uses

Sodium Metasilicate reacts with acids to produce

silica gel Silica gel is an amorphous and porous form of silicon dioxide (silica), consisting of an irregular tridimensional framework of alternating silicon and oxygen atoms with nanometer-scale voids and pores. The voids may contain water or some other l ...

. * 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

References

{{Authority control Inorganic silicon compounds Sodium compounds Metasilicates

Preparation and properties

Structure

Uses

See also

References