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3, 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 [– SiO 2− 3 –] n. It is a colorless crystalline hygroscopic and deliquescent solid, soluble in water (giving an alkaline solution) but not in alcohols. [1]
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 cements , coatings, passive fire protection , textile and lumber processing, manufacture of refractory ...
The tables below provides information on the variation of solubility of different substances (mostly inorganic compounds) in water with temperature, at one atmosphere pressure. Units of solubility are given in grams of substance per 100 millilitres of water (g/(100 mL)), unless shown otherwise. The substances are listed in alphabetical order.
The following chart shows the solubility of various ionic compounds in water at 1 atm pressure and room temperature (approx. 25 °C, 298.15 K). "Soluble" means the ionic compound doesn't precipitate, while "slightly soluble" and "insoluble" mean that a solid will precipitate; "slightly soluble" compounds like calcium sulfate may require heat to precipitate.
Idealized structure of sodium metasilicate. Metasilicates are silicates containing ions of empirical formula SiO 2− 3. Common stoichiometries include M I 2 SiO 3 and M II SiO 3. Metasilicates can be cyclic, usually the hexamer (SiO 3) 12− 6 or chains (SiO 3)n 2−. [1] Common compounds containing metasilicate anion are: Inosilicates
Depiction of a metasilicate chain, emphasizing the tetrahedral silicate subunits. Alternative depiction of a metasilicate chain emphasizing the Si-O bonds. With two shared oxides bound to each silicon, cyclic or polymeric structures can result. The cyclic metasilicate ring Si 6 O 12− 18 is a hexamer of SiO 3 2-.
Theoretical computations indicate that the dissolution of silica in water proceeds through the formation of a SiO 2 ·2H 2 O complex and then orthosilicic acid. [ 7 ] The silicon–oxygen double bond of metasilicic acid, implied by the formula H 2 SiO 3 , is hypothetical or highly unstable.
Sulfuric acid and sodium silicate solutions are added simultaneously with agitation to water. Precipitation is carried out under acidic or basic conditions. The choice of agitation , duration of precipitation, the addition rate of reactants, their temperature and concentration and pH can vary the properties of the resulting silica.