This is caused by breakage of the silica spheres when contacting the water. Some types of silica gel will "pop" when exposed to enough water. Once saturated with water, the gel may be regenerated by heating it to 120 ☌ (250 ☏) for 1–2 hours. However, material silica gel removes moisture by adsorption onto the surface of its numerous pores rather than by absorption into the bulk of the gel. Silica gel is often described as "absorbing" moisture, which may be appropriate when the gel's microscopic structure is ignored, as in silica gel packs or other products. Silica gel's high specific surface area (around 750–800 m 2/g (230,000–240,000 sq ft/oz)) allows it to adsorb water readily, making it useful as a desiccant (drying agent). Stabilizing silica gel - non-crystalline micro-porous solid powder, nontoxic, flame-resisting, used in brewery of grains for beer to improve taste, clearness, color, and foam and for removal of non-micro-organism impurities. Superficial polarity, thermal stability, performance greater than fine-pored silica gel. Silica alumina gel - light yellow, chemically stable, flame-resistant, insoluble except in alkali or hydrofluoric acid. Additionally dried and screened, it forms macro-pored silica gel which is used as drier, adsorbent and catalyst carrier. Type C – translucent, micro-pored structure, raw material for preparation of silica gel cat litter.Type B – translucent white pellets, pore diameter: 4.5–7.0 nm, liquid adsorbents, drier and perfume carriers, also may be used as catalyst carriers, cat litter.Type A – clear pellets, approximate pore diameter: 2.5 nm, drying and moistureproof properties, can be used as catalyst carriers, adsorbents, separators and variable-pressure adsorbent.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, making carbon disulphide, and as a catalyst support for the manufacture of butadiene from ethanol (feedstock for synthetic rubber production). Patrick, a chemistry professor at Johns Hopkins University. The synthetic route for producing silica gel was patented in 1918 by Walter A.
It was used in World War I for the adsorption of vapors and gases in gas mask canisters. Silica gel was in existence as early as the 1640s as a scientific curiosity. 6.6 Humidity indicator (color-changing silica gel).It is sometimes used in laboratory processes, for example to suppress convection in liquids or prevent settling of suspended particles. '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. Small paper envelopes containing silica xerogel pellets, usually with a "do not eat" warning, are often included in dry food packages to absorb any humidity that might cause spoilage of the food. Some grains may contain small amounts of indicator substance that changes color when they have absorbed some water.
Silica xerogel is usually commercialized as coarse granules or beads, a few millimeters in diameter. It is hard and translucent, but considerably softer than massive silica glass or quartz and remains hard when saturated with water. 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. In the last case, the material is properly called silica xerogel. The voids may contain water or some other liquids, or may be filled by gas or vacuum. 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. Colloidal silica gel with light opalescence
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