Hydrated silica
Encyclopedia
Hydrated silica is a form of silicon dioxide
Silicon dioxide
The chemical compound silicon dioxide, also known as silica , is an oxide of silicon with the chemical formula '. It has been known for its hardness since antiquity...

, which has a variable amount of water in the formula. It is also known as silicic acid
Silicic acid
Silicic acid is a general name for a family of chemical compounds of the element silicon, hydrogen, and oxygen, with the general formula [SiOx4-2x]n...

, a term usually used for its form dissolved in water. It is found in nature, as opal
Opal
Opal is an amorphous form of silica related to quartz, a mineraloid form, not a mineral. 3% to 21% of the total weight is water, but the content is usually between 6% to 10%. It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock, being most...

, which has been mined as a gemstone for centuries and in the cell walls of diatoms. It is also manufactured for use in toothpaste
Toothpaste
Toothpaste is a paste or gel dentifrice used with a toothbrush as an accessory to clean and maintain the aesthetics and health of teeth. Toothpaste is used to promote oral hygiene: it serves as an abrasive that aids in removing the dental plaque and food from the teeth, assists in suppressing...

. Once dehydrated the gel is used as a desiccant
Desiccant
A desiccant is a hygroscopic substance that induces or sustains a state of dryness in its local vicinity in a moderately well-sealed container....

 known as Silica gel
Silica gel
Silica gel is a granular, vitreous, porous form of silica made synthetically from sodium silicate. Despite its name, silica gel is a solid. It is a naturally occurring mineral that is purified and processed into either granular or beaded form...

. It is also used in various paints and varnishes and in the production of beer
Beer
Beer is the world's most widely consumed andprobably oldest alcoholic beverage; it is the third most popular drink overall, after water and tea. It is produced by the brewing and fermentation of sugars, mainly derived from malted cereal grains, most commonly malted barley and malted wheat...

.

Nature

In its pure form, as manufactured for toothpaste, it is an odourless, tasteless, white, gelatinous substance, which is chemically inert.

Chemical formula

Chemical Formula: SiO2 · nH2O
SiO2 = 1, H2O = 1: H2SiO3
SiO2 = 1, H2O = 2: H4SiO4 [also known as Si(OH)4]
SiO2 = 2, H2O = 1: H2Si2O5
SiO2 = 2, H2O = 3: H6Si2O7
SiO2 = 3, H2O = 2: H4Si3O8
SiO2 = 3, H2O = 4: H8Si3O10
SiO2 = 4, H2O = 1: H2Si4O9

Use in toothpaste

Diatomaceous earth
Diatomaceous earth
Diatomaceous earth also known as diatomite or kieselgur/kieselguhr, is a naturally occurring, soft, siliceous sedimentary rock that is easily crumbled into a fine white to off-white powder. It has a particle size ranging from less than 1 micrometre to more than 1 millimetre, but typically 10 to...

, originally mined as "tooth powder" is a naturally occurring hydrated silica. As a fine gel abrasive
Abrasive
An abrasive is a material, often a mineral, that is used to shape or finish a workpiece through rubbing which leads to part of the workpiece being worn away...

, frequently combined with softer calcium carbonate
Calcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...

 (from chalk
Chalk
Chalk is a soft, white, porous sedimentary rock, a form of limestone composed of the mineral calcite. Calcite is calcium carbonate or CaCO3. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite plates shed from micro-organisms called coccolithophores....

) it helps to remove plaque
Dental plaque
Dental plaque is a biofilm, usually a pale yellow, that develops naturally on the teeth. Like any biofilm, dental plaque is formed by colonizing bacteria trying to attach themselves to a smooth surface...

. Milled to a slightly larger size, the grains are more aggressive and are used in tooth bleaching
Tooth bleaching
Dental bleaching, also known as tooth whitening, is a common procedure in general dentistry but most especially in the field of cosmetic dentistry. A child's deciduous teeth are generally whiter than the adult teeth that follow. As a person ages the adult teeth often become darker due to changes in...

 formulations.

Flame retardant

It has also, synergetic effects when compounded with traditional flame retardants such as magnesium hydroxide and aluminium hydroxide.

Safety

Hydrated silica is listed by the US Food and Drug Administration
Food and Drug Administration
The Food and Drug Administration is an agency of the United States Department of Health and Human Services, one of the United States federal executive departments...

as "Generally Recognized as Safe".
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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