Sodium silicate

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Description

A white to greenish vitreous solid or clear, syrupy liquid. Sodium silicate is made by fusing silicon dioxide (from Sand) and Sodium oxide (from Soda ash). An aqueous solution of sodium silicate is called Water glass. It forms a hard, glasslike mass when it dries. Sodium silicate has been used to preserve eggs, fireproof fabrics, and waterproof walls. Most commonly, it is used as a cement for abrasive wheels, bonding paper, corrugated boxes and cartons, wood, glass, porcelain, leather, and textiles. A water glass solution is viscous and has little tack. For use as an adhesive, pressure must be applied to hold materials together while bonding. The dried product is brittle and water sensitive. Aluminum salts can be added to the formulation to improve water resistance. Water glass has been used to make artificial stone. It was tried unsuccessfully as a binder in the 19th century for fresco paintings (see Mineral painting). Water glass was also used in the Ransome process of stone preservation. This procedure used alternating solutions of an alkaline silicate and Calcium chloride to form insoluble Calcium silicate in the pores of the stone.

Synonyms and Related Terms

water glass; waterglass; soluble glass; liquid glass; silicate of soda; sodium metasilicate; egg preserver; silicate de sodium (Fr.)

Applications

  • Silica gel packets or beads for moisture control
  • Passive fire control
  • Stone consolidation

Risks

Noncombustible.

Corrosive. Skin contact causes irritation and burns. Ingestion causes vomiting.

PQ Corporation: SDS

Physical and Chemical Properties

Soluble in water forming strongly alkaline solutions (pH = 11-12.5)

Partially miscible with primary alcohols and ketones.

Composition 2Na2O - SiO2
CAS 1344-09-8
Refractive Index 1.513, 1.520, 1.528
Density 1.3-1.5 liquid; 2.40-2.61 (solid)
Boiling Point 102 C (liquid)
Melting Point 1088 C (solid)

Resources and Citations

  • J.H.Wills, "Inorganic Adhesives and Cements" in Handbook of Adhesives, I.Skeist (ed.), Van Nostrand Reinhold, New York, 1977. p.117-138.
  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 738
  • Matt Roberts, Don Etherington, Bookbinding and the Conservation of Books: a Dictionary of Descriptive Terminology, U.S. Government Printing Office, Washington DC, 1982
  • The Dictionary of Paper, American Paper Institute, New York, Fourth Edition, 1980
  • The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry 8824
  • CRC Handbook of Chemistry and Physics, Robert Weast (ed.), CRC Press, Boca Raton, Florida, v. 61, 1980 Comment: ref. index = 1.513, 1.520, 1.528
  • Michael McCann, Artist Beware, Watson-Guptill Publications, New York City, 1979