Hydrated silica

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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[edit]

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

Chemical formula[edit]

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[edit]

Diatomaceous earth, originally mined as "tooth powder" is a naturally occurring hydrated silica. As a fine gel abrasive, frequently combined with softer calcium carbonate (from chalk) it helps to remove plaque. Milled to a slightly larger size, the grains are more aggressive and are used in tooth bleaching formulations.

Flame retardant[edit]

It also has synergetic effects when compounded with traditional flame retardants such as magnesium hydroxide and aluminium hydroxide[citation needed].

Safety[edit]

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

References[edit]

Toothpaste: [1] Chemistry: [2] Opal: [3] Paint/Varnish: [4] Beer: [5]