Silica gel

Silica gel is an amorphous and porous form of silicon dioxide (silica), consisting of an irregular tridimensional framework of alternating silicon and oxygen atoms with nanometer-scale voids and pores.

Notable examples include fused quartz, fumed silica, silica gel, and aerogels.

Silica gel is an amorphous and porous form of silicon dioxide (silica), consisting of an irregular tridimensional framework of alternating silicon and oxygen atoms with nanometer-scale voids and pores.

Increasing water concentration results in the formation of hydrated silica gels and colloidal silica dispersions.

An aqueous solution of sodium silicate is acidified to produce a gelatinous precipitate that is washed, then dehydrated to produce colorless silica gel.

The product has a wide variety of uses, including the formulation of cements, passive fire protection, textile and lumber processing, manufacture of refractory ceramics, as adhesives, and in the production of silica gel.

An alternative indicator is methyl violet which is orange when dry and green when hydrated.

Its main use is as a purple dye for textiles and to give deep violet colors in paint and ink, it is also used as a hydration indicator for silica gel.

It was used in World War I for the adsorption of vapors and gases in gas mask canisters.

Silica gel is a chemically inert, nontoxic, polar and dimensionally stable (< 400 °C) amorphous form of SiO 2.

'Wet' silica gel, as may be freshly prepared from alkali silicate solutions, may vary in consistency from a soft transparent gel, similar to gelatin or agar, to a hard solid, namely a water-logged xerogel.

In the limit, the silicate anions merge into a tridimensional network of silicon tetrahedra, with most oxygen atoms occurring as covalent bridges; which is some form of silica, such as silica gel, mixed with water.

Silica gel is also applied to aluminium, glass, or plastic sheets for thin layer chromatography.

Thin-layer chromatography is performed on a sheet of glass, plastic, or aluminium foil, which is coated with a thin layer of adsorbent material, usually silica gel, aluminium oxide (alumina), or cellulose.

In World War II, silica gel was indispensable in the war effort for keeping penicillin dry, protecting military equipment from moisture damage, as a fluid cracking catalyst for the production of high octane gasoline, and as a catalyst support for the manufacture of butadiene from ethanol (feedstock for synthetic rubber production).

The catalyst is most commonly phosphoric acid, adsorbed onto a porous support such as silica gel or diatomaceous earth.

Silica gel may also be used to keep the relative humidity (RH) inside a high frequency radio or satellite transmission system waveguide as low as possible (see also Humidity buffering).

2. Silica Gel is widely used to buffer relative humidity inside museum display cases, packaged clothing, electronics and anything that might be damaged by condensation, or in the example of museum display cases, being too low an RH (relative humidity) as the silica will help protect the objects displayed from mechanical damage due to shrinking and growing with RH changes.

Silica gel is also combined with alkali metals to form a M-SG reducing agent.

In M-SG an alkali metal is absorbed into silica gel at elevated temperatures.

In column chromatography, the stationary phase is most often composed of silica gel particles of 40–63 μm.

The most common stationary phase for column chromatography is silica gel, the next most common being alumina.

Silica gel may also be used to keep the relative humidity (RH) inside a high frequency radio or satellite transmission system waveguide as low as possible (see also Humidity buffering).

Moisture in waveguides can typically be prevented with silica gel, a desiccant, or slight pressurization of the waveguide cavities with dry nitrogen or argon.

In chemistry, silica gel is used in chromatography as a stationary phase.

However, instead of using a stationary phase of paper, it involves a stationary phase of a thin layer of adsorbent like silica gel, alumina, or cellulose on a flat, inert substrate.

Silica gel may be doped with a moisture indicator that gradually changes its color when it transitions from the anhydrous (dry) state, to the hydrated (wet) state.

Common desiccants include phosphorus pentoxide and silica gel.

(See SiGNa chemistry)

SiGNa chemistry is a type of chemistry in which alkali metals are encapsulated into porous oxides of silica gel in order to reduce their pyrophoric and highly combustible properties while preserving the desirable reduction reactivity of the metals (Dye, et al.).

Silica gel is also used as cat litter, by itself or in combination with more traditional materials, such as clays including bentonite.

Silica gel litter, often referred to as "crystal litter", is a porous granular form of silicon dioxide, has the highest absorbency of any litter, and has excellent moisture control and complete odor elimination for an extended period of time compared to other litters.

Silica gel is also used as cat litter, by itself or in combination with more traditional materials, such as clays including bentonite.

In fact, in the most common package environments, bentonite desiccants offer a higher adsorption capacity than silica gel desiccants.

Silica gel is an amorphous and porous form of silicon dioxide (silica), consisting of an irregular tridimensional framework of alternating silicon and oxygen atoms with nanometer-scale voids and pores.

Silica gel is an amorphous and porous form of silicon dioxide (silica), consisting of an irregular tridimensional framework of alternating silicon and oxygen atoms with nanometer-scale voids and pores.

Silica gel is an amorphous and porous form of silicon dioxide (silica), consisting of an irregular tridimensional framework of alternating silicon and oxygen atoms with nanometer-scale voids and pores.

Silica gel is an amorphous and porous form of silicon dioxide (silica), consisting of an irregular tridimensional framework of alternating silicon and oxygen atoms with nanometer-scale voids and pores.

The voids may contain water or some other liquids, or may be filled by gas or vacuum.

Silica xerogel with an average pore size of 2.4 nanometers has a strong affinity for water molecules and is widely used as a desiccant.

It is hard and translucent, but considerably softer than massive silica glass or quartz; and remains hard when saturated with water.

It is hard and translucent, but considerably softer than massive silica glass or quartz; and remains hard when saturated with water.