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|Section2= |Section3= |Section4= |Section8= }} Sodium silicate is the common name for compounds with the formula Na2(SiO2)nO. A well-known member of this series is sodium metasilicate, Na2SiO3. Also known as waterglass or liquid glass, these materials are available in aqueous solution and in solid form. The pure compositions are colourless or white, but commercial samples are often greenish or blue owing to the presence of iron-containing impurities. They are used in cements, passive fire protection, textile and lumber processing, refractories, and automobiles. Sodium carbonate and silicon dioxide react when molten to form sodium silicate and carbon dioxide: :Na2CO3 + SiO2 → Na2SiO3 + CO2 Anhydrous sodium silicate contains a chain polymeric anion composed of corner-shared tetrahedral, and not a discrete SiO32− ion.〔 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.〔Wells A.F. (1984) ''Structural Inorganic Chemistry'' 5th edition Oxford Science Publications ISBN 0-19-855370-6〕 In industry, the various grades of sodium silicate are characterized by their SiO2:Na2O weight ratio (weight ratios can be converted to molar ratios by multiplication with 1.032), which can vary between 2:1 and 3.75:1.〔Gerard Lagaly, Werner Tufar, A. Minihan, A. Lovell "Silicates" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, 2005. 〕 Grades with this ratio below 2.85:1 are termed alkaline. Those with a higher SiO2:Na2O ratio are described as neutral. ==History== Water glass〔See also: * Leopold Wolff, ''Das Wasserglas: Seine Darstellung, Eigenschaften und seine mannichfache Anwendung in den technischen Gewerben'' ( its preparation, properties, and its manifold uses in technical commerce ) (Leipzig, (Germany): Quedlinburg, 1846). * Emile Kopp (1857) "Sur la préparation et les propriétés du verre soluble ou des silicates de potasse et de soude; analyse de tous les travaux publiés jusqu'a ce jour sur ce sujet" (On the preparation and properties of water-glass or the silicates of potash and soda; analysis of all works published until today on this subject) ''Le Moniteur scientifique'', 1 : (337-349 ), (366-391 ). * Hermann Krätzer, ''Wasserglas und Infusorienerde, deren Natur und Bedeutung für Industrie, Technik und die Gewerbe'' (and soluble earths, their nature and significance for industry, technology, and commerce ) (Vienna (Wien), Austria: Hartleben, 1887). * Hermann Mayer, ''Das Wasserglas; Sein Eigenschaften, Fabrikation und Verwendung auf Grund von Erfahrungen und Mitteilungen der Firma Henkel & Cie''. ( Its properties, production, and application on the basis of experiences and communications of the firm of Henkel & Co. ) (Braunschweig, Germany: Vieweg, 1925). * Morris Schrero, (''Water-glass: A Bibliography'' ) (Pittsburgh, Pennsylvania: Carnegie Library, 1922).〕 was defined in Von Wagner's ''Manual of Chemical Technology'' (1892 translation) as any of the soluble alkaline silicates, first observed by Jean Baptist van Helmont ''circa'' 1640 as a fluid substance made by melting sand with excess alkali.〔Johannes van Helmont, ''Opuscula medica inaudita'', (Cologne (Coloniæ Agrippinæ), (Germany): Jost Kalckhoven (Jodocum Kalcoven), 1644), part I: De Lithiasi. On (page 53 ), van Helmont mentions that alkalis dissolve silicates: "''Porro lapides, gemmae, arenae, marmora, silices, &c. adjuncto alcali, vitrificantur: sin autem plure alcali coquantur, resolvuntur in humido quidem: ac resoluta, facili negotio acidorum spirituum, separantur ab alcali, pondere pristini pulveris lapidum''." (Furthermore, stone, gems, sand, marble, silica, etc., become glassy by the addition of alkali: but if roasted with more alkali, they are dissolved in moisture: and the former weight of the stone powder is separated from the alkali and released by simply adding acid.)〕〔A number of other alchemists supposedly discovered potassium silicate before van Helmont. See: * Giambattista della Porta in his book ''Magia naturalis sive de miraculis rerum naturalium'' (1567), mentions that cream of tartar (''tartari salis'') causes powdered quartz (''crystallum'') to melt at a lower temperature. See: Baptista Porta, ''Magia naturalis sive de miraculis rerum naturalium, libri iiii'' (magic or on the miracles of nature, in four books ) (Lyon (Lugdunum), France: Guillaume Rouillé (Gulielmum Rovillium), 1569), (pages 290-291, "Crystallus, ut fusilis fiat" (quartz, so made molten) ). * Some evidence indicates the alchemist Basil Valentine prepared potassium silicate in 1520. See: Kohn, C. (1862) "Die Erfindung des Wasserglas im Jahre 1520" (The invention of waterglass in the year 1520), ''Zeitschrift des Oesterreichischen Ingenieur-Vereins'' (Journal of the Austrian Engineer Association), 14 : 229-230. However, subsequently an article pointed out that the substance prepared by Basil Valentine in 1520, by Agricola in 1550, by van Helmont around 1640, and by Glauber in 1648 was not the waterglass that Fuchs produced in 1818. See: : * Anon. (1863) ("Die Erfindung des Wasserglases im Jahre 1520," ) ''Kunst- und Gewerbe-Blatt'', 49 : 228-230. : * Reprinted in: Anon. (1863) ("Die Erfindung des Wasserglases im Jahre 1520," ) ''Polytechnisches Journal'', 168 : 394-395. : * Reprinted in: Anon. (1863) ("Die angebliche Erfindung des Wasserglases im Jahre 1520" ) (On the alleged invention of waterglass in the year 1520), ''Neues Repertorium für Pharmacie'', 12 : 271-273.〕 Glauber made what he termed "liquor silicum" in 1646 from potash and silica.〔Johann Rudolf Glauber, ''Furni Novi Philosophici'' (philosophical furnace ) (Amsterdam: Johan Jansson, 1646). In the 1661 German-language edition, see Chapter ("LXXIX. Wie durch Hülff eines reinen Sandes oder Kißlings / auß Sale Tartari ein kräfftiger Spiritus kan erlanget werden." ) (How with the help of a pure sand or silica / a powerful solution can be gotten from cream of tartar). Glauber's recipe for ''liquor silicum'' (potassium silicate) appears on pages 164-166. The recipe is simple: Potassium hydrogen tartrate (cream of tartar, ''Sale tartari'', ''Weinstein'' ) is heated in a furnace until it is converted to potassium carbonate. The potassium carbonate is mixed with sand in a crucible and heated until the mixture melts. The mixture is maintained in a liquid state until it ceases to bubble (due to the release of carbon dioxide from the potassium carbonate). The mixture is allowed to cool and then pulverized to a fine powder. When the powder is exposed to moist air, it gradually forms a viscous liquid, which Glauber called "''Oleum oder Liquor Silicum, Arenæ, vel Crystallorum''" (i.e., oil or solution of silica, sand or () crystal).〕 Johann Nepomuk von Fuchs, in 1818, obtained what is now known as water glass by treating silicic acid with an alkali, the result being soluble in water, "but not affected by atmospheric changes".〔See: * Joh. Nep. Fuchs (1825) ("Ueber ein neues Produkt aus Kieselerde und Kali" ) (On a new product from silica and potash), ''Archiv für die gesammte Naturlehre'', 5 (4) : 385-412. On page 386, Fuchs states that he first prepared potassium silicate in 1818: "Ich erhielt es zuerst, vor ungefähr 7 Jahren, …" (I first obtained it about 7 years ago, … ); since the Fuchs' paper was published in 1825, 7 years earlier would be 1818. * Reprinted in: Joh. Nepomuk Fuchs (1825) ("''Ueber ein neues Produkt aus Kieselerde und Kali; und dessen nüzliche Anwendung als Schuzmittel gegen schnelle Verbreitung des Feuers in Theatern, als Bindemittel, firnißartigen Anstrichen u.s.w.''" ) (On a new product from silica and potash; and its useful application as a protection against the rapid spread of fire in theaters, as a glue, varnish, etc.) ''Polytechnisches Journal'', 17 : 465-481.〕〔VonWagner, Rudolf (1892 translation of 13th edition by Willian Crookes) ''Manual of Chemical Technology'' ()〕 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Sodium silicate」の詳細全文を読む スポンサード リンク
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