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 meta silicic acid, H 2SiO 3. 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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