Sodium silicate
History

Soluble silicates of alkali metals (sodium or potassium) were observed by European alchemists in the 16th century. Giambattista della Porta observed in 1567 that tartari salis (cream of tartar, potassium bitartrate) caused powdered crystallum (quartz) to melt at a lower temperature. Other possible early references to alkali silicates were made by Basil Valentine in 1520, and by Agricola in 1550. Around 1640, Jan Baptist van Helmont reported the formation of alkali silicates as a soluble substance made by melting sand with excess alkali, and observed that the silica could be precipitated quantitatively by adding acid to the solution.

In 1646, Glauber made potassium silicate, which he called liquor silicum, by melting potassium carbonate (obtained by calcinating cream of tartar) and sand in a crucible, and keeping it molten until it ceased to bubble (due to the release of carbon dioxide). The mixture was allowed to cool and then was ground to a fine powder. When the powder was exposed to moist air, it gradually formed a viscous liquid, which Glauber called " Oleum oder Liquor Silicum, Arenæ, vel Crystallorum " (i.e., oil or solution of silica, sand or quartz crystal).

However, it was later claimed that the substances prepared by those alchemists were not waterglass as it is understood today. That would have been prepared in 1818 by Johann Nepomuk von Fuchs, by treating silicic acid with an alkali; the result being soluble in water, "but not affected by atmospheric changes".

The terms "water glass" and "soluble glass" were used by Leopold Wolff in 1846, by Émile Kopp in 1857, and by Hermann Krätzer in 1887.

In 1892, Rudolf Von Wagner distinguished soda, potash, double (soda and potash), and fixing (i.e., stabilizing) as types of water glass. The fixing type was "a mixture of silica well saturated with potash water glass and a sodium silicate" used to stabilize inorganic water color pigments on cement work for outdoor signs and murals.
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