Silica
Description
Colorless crystals or white amorphous powder. Silica is widely available because it makes up one of the largest portions of the earth's crust. In its purest form, silica, or silicon dioxide, occurs as crystalline Quartz. The more common, but less pure, forms are Quartzite, Sandstone, Flint, Agate, and Sand. The fossil form of silica is Diatomaceous earth. All forms of silica are inert, unaffected by heat, insoluble in strong acids (except hydrofluoric) and slowly attacked by strong alkalis. Silica is not commonly used as a pigment, however, it is found in grounds, primers and wood fillers. Silica is used in the manufacture of glass, water glass, abrasives, ceramics and enamelware.
| Compound | Description | Examples | Applications | ||||
|---|---|---|---|---|---|---|---|
| Silica | Pure silica is crystalline silicon dioxide found in nature as as quartz. Variations due to temperature and pressure produce amorphous, vitreous or glassy forms of silica. | quartz, sand, quartzite, sandstone, flint agate, diatomaceous earth | production of glass and ceramics; use as a filler in concrete; as an abrasive | ||||
| Fumed silica | A white fluffy powder containg a colloidal form of silica produced by burning silicon tetrachloride. Untreated fumed silica is hydrophilic, but many commercial products are treated to make them hydrophobic | Aerosil; Cab-O-Sil; HDK; Zandosil; Reolosil; Orisil; XYSIL | thixotropic thickener, anti-caking agent, filtration; desiccant to kill insects | ||||
| Silica gel | An amorphous, porous form of silica available as granules or beads. It has a strong affinity for water. | Grade 40; Grade 42; Arten Gel; ArtSorb: Britesorb; Prosorb; Rhapid Gel; Rhapid pak | desiccant, sorbent, humidity buffering | ||||
Synonyms and Related Terms
silicon dioxide; silicic anhydride; quartz; silex; diatomaceous earth; flint; diatomite; sand; quartzite; sandstone; amethyst; jasper, chalcedony; agate; onyx; tridymite; opal; cristobalite; Pigment White 27; Siliziumdioxid (Deut.); Kieselgur (Deut.); Kieselerde (Deut.); silice (Fr., Esp., It.); chalazias (Gr.); kwarts (Ned.); sílica (Port.)
Risks
- Noncombustible.
- Toxic by inhalation.
- Chronic exposure to dust may cause silicosis
Physical and Chemical Properties
- Inert
- Soluble in hydrofluoric acid.
- Density (g/ml) = 2.2 (amorphous) and 2.65 (quartz).
| Composition | SiO2 |
|---|---|
| Melting Point | 1710 C |
| Boiling Point | 2230 C |
Comparisons
Properties of Common Abrasives
Characteristics of Common White Pigments
Resources and Citations
- Wikipedia: Silicon dioxide Accessed July 2023
- R. J. Gettens, G.L. Stout, Painting Materials, A Short Encyclopaedia, Dover Publications, New York, 1966
- G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 708
- Ralph Mayer, A Dictionary of Art Terms and Techniques, Harper and Row Publishers, New York, 1969 (also 1945 printing)
- Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
- Michael McCann, Artist Beware, Watson-Guptill Publications, New York City, 1979
- Matt Roberts, Don Etherington, Bookbinding and the Conservation of Books: a Dictionary of Descriptive Terminology, U.S. Government Printing Office, Washington DC, 1982
- Dictionary of Building Preservation, Ward Bucher, ed., John Wiley & Sons, Inc., New York City, 1996
- Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997
- The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry 8637
- The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998
- Art and Architecture Thesaurus Online, https://www.getty.edu/research/tools/vocabulary/aat/, J. Paul Getty Trust, Los Angeles, 2000