Hydrated silica is a form of
silicon dioxide, which has a variable amount of water in the formula. When dissolved in water it is usually known as
silicic acid
Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...
. It is found in nature, as
opal
Opal is a hydrated amorphous form of silica (SiO2·''n''H2O); its water content may range from 3 to 21% by weight, but is usually between 6 and 10%. Due to its amorphous property, it is classified as a mineraloid, unlike crystalline forms o ...
(which has been mined as a gemstone for centuries), and in the cell walls of
diatoms
A diatom ( Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group comprising se ...
. It is also manufactured for use in
toothpaste
Toothpaste is a paste or gel dentifrice used with a toothbrush to clean and maintain the aesthetics and health of teeth. Toothpaste is used to promote oral hygiene: it is an abrasive that aids in removing dental plaque and food from the teeth, a ...
. Hydrated silica can be dehydrated to produce
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. The voids may contain water or some other ...
, which is used as a
desiccant
A desiccant is a hygroscopic substance that is used to induce or sustain a state of dryness (desiccation) in its vicinity; it is the opposite of a humectant. Commonly encountered pre-packaged desiccants are solids that absorb water. Desiccants ...
. It is also used in various paints and varnishes and in the production of
beer.
Nature
In its pure form, as manufactured for toothpaste, it is an odorless, tasteless, white, gelatinous substance, which is chemically inert.
Chemical formula
Chemical Formula: SiO
2 · H
2O
: 1 SiO
2 + 1 H
2O → H
2SiO
3
: 1 SiO
2 + 2 H
2O → H
4SiO
4 lso known as Si(OH)4: 2 SiO
2 + 1 H
2O → H
2Si
2O
5
: 2 SiO
2 + 3 H
2O → H
6Si
2O
7
: 3 SiO
2 + 2 H
2O → H
4Si
3O
8
: 3 SiO
2 + 4 H
2O → H
8Si
3O
10
: 4 SiO
2 + 1 H
2O → H
2Si
4O
9
Use in toothpaste
Diatomaceous earth
Diatomaceous earth (), diatomite (), or kieselgur/kieselguhr is a naturally occurring, soft, siliceous sedimentary rock that can be crumbled into a fine white to off-white powder. It has a particle size ranging from more than 3 μm to le ...
, originally mined as "tooth powder" is a naturally occurring hydrated silica. As a fine gel
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 by friction. While finishing a material often means polishing it to gain a smooth, reflec ...
, frequently combined with softer
calcium carbonate (from
chalk
Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor. Chalk ...
) it helps to remove
plaque
Plaque may refer to:
Commemorations or awards
* Commemorative plaque, a plate or tablet fixed to a wall to mark an event, person, etc.
* Memorial Plaque (medallion), issued to next-of-kin of dead British military personnel after World War I
* Pla ...
. Milled to a slightly larger size, the grains are more aggressive and are used in
tooth bleaching
Tooth whitening or tooth bleaching is the process of lightening the color of human teeth. Whitening is often desirable when teeth become yellowed over time for a number of reasons, and can be achieved by changing the intrinsic or extrinsic color o ...
formulations.
Flame retardant
It also has synergetic effects when compounded with traditional
flame retardant
The term flame retardants subsumes a diverse group of chemicals that are added to manufactured materials, such as plastics and textiles, and surface finishes and coatings. Flame retardants are activated by the presence of an ignition source an ...
s such as
magnesium hydroxide
Magnesium hydroxide is the inorganic compound with the chemical formula Mg(OH)2. It occurs in nature as the mineral brucite. It is a white solid with low solubility in water (). Magnesium hydroxide is a common component of antacids, such as milk ...
and
aluminium hydroxide
Aluminium hydroxide, Al(OH)3, is found in nature as the mineral gibbsite (also known as hydrargillite) and its three much rarer polymorphs: bayerite, doyleite, and nordstrandite. Aluminium hydroxide is amphoteric, i.e., it has both basic and ...
.
Safety
Hydrated silica is listed by the US
Food and Drug Administration
The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food s ...
as "Generally Recognized as Safe"
[https://web.archive.org/web/20071126082443/http://www.tomsofmaine.com/toms/ifs/hydrated_silica.asp]
References
Toothpaste
Chemistry
Opal
Paint/Varnish
Beer
{{DEFAULTSORT:Hydrated Silica
Household chemicals
Silicon dioxide