Silica/silika og silica gel

Silicon:

• Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a tetravalent metalloid and semiconductor.

• Silica:

  • Silicon dioxide
  • Kjemisk formel: SiO₂

  • _{most commonly found in nature as quartz and in various living organisms.^[5][6] In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and most abundant families of materials, existing as a compound of several minerals and as a synthetic product. Notable examples include fused quartz, fumed silica, silica gel, and aerogels. It is used in structural materials, microelectronics (as an electrical insulator), and as components in the food and pharmaceutical industries.}

  • _{The solubility of silicon dioxide in water strongly depends on its crystalline form}

  • Silica is the primary ingredient in the production of most glass. When molten silicon dioxide SiO₂ is rapidly cooled, it does not crystallize, but solidifies as a glass. Because of this, most ceramic glazes have silica as the main ingredient.

    The majority of optical fibers for telecommunication are also made from silica. It is a primary raw material for many ceramics such as earthenware, stoneware, and porcelain.

    Silicon dioxide is used to produce elemental silicon.

  • Silica gel:

    • Kjemisk formel: SiO₂
    • _{the material is properly called silica xerogel.}
    • _{may contain small amounts of indicator substance that changes color when they have absorbed some water.}
    • _{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. 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.}
    • _{Once saturated with water, the gel may be regenerated by heating it to 120 °C (250 °F) for 1–2 hours. Some types of silica gel will "pop" when exposed to enough water. This is caused by breakage of the silica spheres when contacting the water.}

    • Silica gel, also referred to as silicon dioxide or synthetic amorphous silica (SAS), is listed by the FDA in the United States as generally recognized as safe (GRAS), meaning it can be added to food products without needing approval. Silica is allowed to be added to food in the USA at up to 2% as permitted under 21 CFR 172.480. In the EU, it can be in up to 5% concentrations.^[12] In 2018, a re-evaluation by the EFSA Panel on Food Additives and Nutrient Sources added to Food found no indications of toxicity even at the highest estimates of exposure level. ^[13]

      Listed uses include: anticaking agent, defoaming agent, stabilizer, adsorbent, carrier, conditioning agent, chillproofing agent, filter aid, emulsifying agent, viscosity control agent, and anti-settling agent.^[14] Silica can be found commonly in foods including baked goods, spices and herbs, dairy products, cocoa products, and more.

    • Types:

      • 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.
      • 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 C – translucent, micro-pored structure, raw material for preparation of silica gel cat litter. Additionally dried and screened, it forms macro-pored silica gel which is used as drier, adsorbent and catalyst carrier.