Silica Gel (redirected from Silica gel crystals)

silica gel, chemical compound. It is a colloidal form of silica, and usually resembles coarse white sand. It may be prepared by partial dehydration of metasilicic acid, H₂SiO₃. Because it has many tiny pores, it has great adsorptive power. It is used as a drying agent, as a catalyst or catalyst carrier, and in purifying various substances. Silica aerogel is fully dehydrated silica gel; it is very porous and is often used in insulation, e.g., for refrigerators.

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silica gel

A highly absorbent form of silicon dioxide often wrapped in small bags and packed with equipment to absorb moisture during shipping and storage.

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silica gel [′sil·ə·kə ¦jel]

(inorganic chemistry)

A colloidal, highly absorbent silica used as a dehumidifying and dehydrating agent, as a catalyst carrier, and sometimes as a catalyst.

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silica gel, synthetic silica

A form of silica which adsorbs moisture readily; used as a drying agent.

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Silica Gel 

the desiccated gel of polysilicic acid; a solid hy-drophilic sorbent. By composition, silica gel is silicon dioxide (silica), and by structure, a highly porous body composed of extremely minute, accreted spherical particles.

In the manufacture of silica gel, a solution of sodium or potassium silicate (water glass) is first acted upon by hydrochloric or sulfuric acid. The congealed product is then broken into pieces, rinsed with water, dried, ground, fractionated, and roasted to remove all moisture. Commercial silica gel is available in grains or globular granules 5-7 to 10-² mm in size. Various brands of silica gel have a mean effective pore diameter of 20–150 angstroms and a specific surface of 10²-10³ m²/g.

Silica gel is used to absorb water vapor and the vapors of organic solvents. It is also used for the absorptive purification of nonpolar liquids and for the separation of alcohols, amino acids, vitamins, and antibiotics in gas and liquid chromatography. Macroporous silica gel serves as a catalyst base.

REFERENCE

Kol’tsov, S. I., and V. B. Aleskovskii. Silikagel’, ego stroenie i khimiches-kiesvoistva. Leningrad, 1963.