Silica Gel Packets |
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These commonly found desiccants are small beads of silica gel inside paper packets. |
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.