Silica gel

Silica gel is a porous, amorphous form of silicon dioxide whose large internal surface adsorbs molecules, especially water. It is used in drying, separation, and purification.

Adsorption: Adsorption is the accumulation of atoms, ions, or molecules on a surface. Water and other molecules attach to silica gel’s extensive internal surfaces rather than entering its solid structure.
Desiccant: A desiccant is a material that removes moisture from its surroundings by adsorption or absorption. Silica gel is a widely used solid desiccant in packages and equipment.
Silicon dioxide: Silicon dioxide is a chemical compound of silicon and oxygen, found in crystalline and amorphous forms. Silica gel is an amorphous, porous form of this compound.
Molecular sieve: A molecular sieve is a porous material with pores that selectively admit molecules according to size or affinity. Unlike silica gel’s broad surface adsorption, molecular sieves can strongly favor particular molecule sizes.
Capillary condensation: Capillary condensation is the formation of liquid in narrow pores at vapor pressures below bulk saturation. At higher humidity, water can condense inside silica gel pores and increase its uptake.
Thin-layer chromatography: Thin-layer chromatography separates mixture components on a coated plate as a solvent moves across it. Silica gel commonly forms the stationary adsorbent layer on chromatography plates.
Amorphous solid: An amorphous solid lacks the long-range, repeating atomic order found in crystals. Silica gel’s disordered silica network distinguishes it from crystalline quartz.
Activated alumina: Activated alumina is a porous, high-surface-area form of aluminum oxide used for adsorption and drying. It competes with silica gel as a regenerable solid desiccant and adsorbent.
Surface hydroxylation: Surface hydroxylation is the formation or presence of hydroxyl groups on a material’s surface. Silica gel’s surface silanol groups interact with adsorbed water.
Flash chromatography: Flash chromatography separates compounds by forcing solvent through a packed column under pressure. Silica gel is a common stationary phase for rapidly separating organic mixtures.

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