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 dessicant known as Silica Gel. It is also used in various paints and varnishes and in the production of beer.

Additional recommended knowledge

Correct Test Weight Handling Guide: 12 Practical Tips

Essential Laboratory Skills Guide

Weighing the right way

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