Hydrated silica

Hydrated silica is a form of silicon dioxide, which has a variable amount of water in the formula. It is also known as silicic acid, a term usually used for its form dissolved in water. It is found in nature, as opal, which has been mined as a gemstone for centuries and in the cell walls of diatoms. It is also manufactured for use in toothpaste. Once dehydrated the gel is used as a desiccant known as Silica gel. 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 odourless, tasteless, white, gelatinous substance, which is chemically inert.

Chemical formula

Chemical Formula: SiO₂ · nH₂O SiO₂ = 1, H₂O = 1: H₂SiO₃ 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 SiO₂ = 4, H₂O = 2: H₄SiO₄ [also known as Si(OH)₄ ]

Use in toothpaste

Hydrated silica is a mild gel abrasive, which, when combined with calcium carbonate (from chalk) helps to remove plaque. Milled to a slightly larger size, the grains are more abrasive and will help to whiten teeth.

Safety

Hydrated silica is listed by the US Food and Drug Administration as "Generally Recognised as Safe".

References

Toothpaste: [http://www.tomsofmaine.com/toms/ifs/hydrated_silica.asp] Chemistry: [http://sci-toys.com/ingredients/hydrated_silica.html] Opal: [http://www.galleries.com/minerals/mineralo/opal/opal.htm] Paint/Varnish: [http://householdproducts.nlm.nih.gov/cgi-bin/household/brands?tbl=chem&id=1683] Beer: [http://www.freepatentsonline.com/4975405.html]