Redir: Silica

The chemical compound silicon dioxide, also known as silica or silox (from the Latin "silex"), is an oxide of silicon, chemical formula Oxygen: 2, and has been known for its hardness since the 9th century. Silica is most commonly found in nature as sand or quartz, as well as in the cell walls of diatoms. It is a principal component of most types of glass and substances such as concrete. Silica is the most abundant mineral in the earth's crust.

Manufactured forms

• glass (a colorless, high-purity form is called fused silica)
• synthetic amorphous silica, silica gel
• pyrogenic silica (sometimes called fumed silica or silica fume)

It is used in the production of various products.

• Inexpensive soda-lime glass is the most common and typically found in drinking glasses, bottles, and windows.
• A raw material for many whiteware ceramics such as earthenware, stoneware and porcelain.
• A raw material for the production of Portland cement.
• A food additive, primarily as a flow agent in powdered foods, or to absorb water (see the ingredients list for).
• The natural ("native") oxide coating that grows on silicon is hugely beneficial in microelectronics. It is a superior electric insulator, with high chemical stability. In electrical applications, it can protect the silicon, store charge, block current, and even act as a controlled pathway to allow small currents to flow through a device. At room temperature, however, it grows extremely slowly, and so to manufacture such oxide layers, the traditional method has been heating of silicon in high-temperature furnaces within an oxygen ambient (thermal oxidation).
• Raw material for aerogel in the Stardust spacecraft
• Used in the extraction of DNA and RNA due to its ability to bind to the nucleic acids under the presence of chaotropes.
• Added to medicinal anti-foaming agent, like Simethicone, in a small proportion to enhance defoaming activity.
• As hydrated silica in toothpaste (abrasive to remove plaque.)
• As a pesticide as Diatomaceous Earth.
• As a high-temperature thermal protection fabric (http://www.firesleeveandtape.com/silica-high-temperature-fabric.html)
• In cosmetics for its light-diffusing properties.

Inhalation health effects

Inhaling powder of any kind (other than prescribed medicines) is not recommended. When considering potential inhalation effects of silica, it is important to understand whether the silica is crystalline (such as quartz) or amorphous (non-crystalline). See the structure and properties section below for more information on which forms are crystalline and non-crystalline.