Hydrated silica

<h2 id="use-in-toothpaste">Use in toothpaste</h2>
<a href="/facts/Diatomaceous_earth/kQVwJICV">Diatomaceous earth</a>, originally mined as "tooth powder" is a naturally occurring hydrated silica. As a fine gel <a href="/facts/Abrasive/UJ9TvVMx">abrasive</a>, frequently combined with softer <a href="/facts/Calcium_carbonate/UQ1wLFna">calcium carbonate</a> (from <a href="/facts/Chalk/b6hepsNS">chalk</a>) it helps to remove <a href="/facts/Dental_plaque/b67GE1pA">plaque</a>. Milled to a slightly larger size, the grains are more aggressive and are used in <a href="/facts/Tooth_bleaching/82tgxhvD">tooth bleaching</a> formulations.<a class="footnote-ref" id="fnref:3" href="#fn:3">3</a> Hydrated silica is a useful abrasive in toothpastes because it does not chemically interact with other active ingredients, especially <a href="/facts/Sodium_fluoride/HHcvwK7s">sodium fluoride</a>.<a class="footnote-ref" id="fnref:4" href="#fn:4">4</a>

<h2 id="nature">Nature</h2>
Hydrated silicas can form in nature through biotic processes primarily involving benthic microorganism activity in the oceans.<a class="footnote-ref" id="fnref:5" href="#fn:5">5</a> However, there are several abiotic processes that form hydrated silicas, such as precipitating out of solution, forming a diagenetic alteration product, or replacing pre-existing minerals in sedimentary rocks.<a class="footnote-ref" id="fnref:6" href="#fn:6">6</a>
In its pure form, as manufactured for toothpaste, it is an odorless, tasteless, white, gelatinous substance, which is chemically inert. One of the primary industrial methods to acquire hydrated silica is through a <a href="/facts/Sol%E2%80%93gel_process/u4vtn2uj">sol-gel process</a>.<a class="footnote-ref" id="fnref:7" href="#fn:7">7</a> 
Hydrated silicas can be categorized into three main categories based on differences in crystallinity:<a class="footnote-ref" id="fnref:8" href="#fn:8">8</a>

<ol><li>Hydrated silicate glass (Lowest crystallinity)</li>
<li>Opal</li>
<li>Microcrystalline quartz (Highest crystallinity)</li></ol>
One of the most common ways to detect and identify hydrated silicas in laboratory is through near infrared and thermal infrared <a href="/facts/Spectroscopy/mj71FuNK">spectroscopy</a>.<a class="footnote-ref" id="fnref:9" href="#fn:9">9</a>

<h2 id="chemical-formula">Chemical formula</h2>
Chemical Formula: SiO2 · nH2O 

1 SiO2 + 1 H2O → H2SiO3
1 SiO2 + 2 H2O → H4SiO4 [also known as Si(OH)4]
2 SiO2 + 1 H2O → H2Si2O5
2 SiO2 + 3 H2O → H6Si2O7
3 SiO2 + 2 H2O → H4Si3O8
3 SiO2 + 4 H2O → H8Si3O10
4 SiO2 + 1 H2O → H2Si4O9
Hydrated silicas exhibit a trend of decreasing bonded water molecules as the crystallinity of the silica molecule increases, with microcrystalline quartz's typically containing the least water content and macrocrystaline quartz having negligible water.<a class="footnote-ref" id="fnref:10" href="#fn:10">10</a>

<h2 id="flame-retardant">Flame retardant</h2>
Hydrated silica compounds, such as hydrated silica aluminate (HSA), can be combined with traditional flame retardants, such as <a href="/facts/Magnesium_hydroxide/0hKR5Ica">magnesium hydroxide</a> and <a href="/facts/Aluminium_hydroxide/e0pXvDGr">aluminium hydroxide</a>, to increase their effectivity.<a class="footnote-ref" id="fnref:11" href="#fn:11">11</a> A hydrated silica compound's effectiveness as a flame retardant is dependent upon the presence of chemically bonded transition metals, commonly iron and titanium<a class="footnote-ref" id="fnref:12" href="#fn:12">12</a>

<h2 id="safety">Safety</h2>
Hydrated silica is listed by the US <a href="/facts/Food_and_Drug_Administration/rCEnh9WB">Food and Drug Administration</a> as "Generally Recognized as Safe" <a class="footnote-ref" id="fnref:13" href="#fn:13">13</a>

Toothpaste: <a href="https://web.archive.org/web/20071126082443/http://www.tomsofmaine.com/toms/ifs/hydrated_silica.asp">[1]</a>
Chemistry: <a href="http://sci-toys.com/ingredients/hydrated_silica.html">[2]</a>[unreliable source?]
Opal: <a href="http://www.galleries.com/minerals/mineralo/opal/opal.htm">[3]</a>
Paint/Varnish: <a href="https://www.whatsinproducts.com/chemicals/view/1/1683">[4]</a>
Beer: <a href="http://www.freepatentsonline.com/4975405.html">[5]</a>

<h2 id="references">References</h2>

<ol>
<li id="fn:1">"Amethyst Galleries: Opal". <a href="http://www.galleries.com/Opal" target="_blank">http://www.galleries.com/Opal</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></li>
<li id="fn:2">"Hydrated silica gel for stabilization treatment of beer". <a href="https://www.freepatentsonline.com/4975405.html" target="_blank">https://www.freepatentsonline.com/4975405.html</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></li>
<li id="fn:3">https://web.archive.org/web/20071126082443/http://www.tomsofmaine.com/toms/ifs/hydrated_silica.asp [bare URL] <a href="https://web.archive.org/web/20071126082443/http://www.tomsofmaine.com/toms/ifs/hydrated_silica.asp" target="_blank">https://web.archive.org/web/20071126082443/http://www.tomsofmaine.com/toms/ifs/hydrated_silica.asp</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></li>
<li id="fn:4">Hara, Anderson T.; Turssi, Cecilia P. (2017-11-01). "Baking soda as an abrasive in toothpastes: Mechanism of action and safety and effectiveness considerations". The Journal of the American Dental Association. 148 (11): S27 – S33. doi:10.1016/j.adaj.2017.09.007. ISSN 0002-8177. PMID 29056187. <a href="https://jada.ada.org/article/S0002-8177(17)30812-7/fulltext" target="_blank">https://jada.ada.org/article/S0002-8177(17)30812-7/fulltext</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></li>
<li id="fn:5">Smith, Matthew R.; Bandfield, Joshua L.; Cloutis, Edward A.; Rice, Melissa S. (2013-04-01). "Hydrated silica on Mars: Combined analysis with near-infrared and thermal-infrared spectroscopy". Icarus. 223 (2): 633–648. Bibcode:2013Icar..223..633S. doi:10.1016/j.icarus.2013.01.024. ISSN 0019-1035. <a href="https://www.sciencedirect.com/science/article/pii/S0019103513000390" target="_blank">https://www.sciencedirect.com/science/article/pii/S0019103513000390</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></li>
<li id="fn:6">Smith, Matthew R.; Bandfield, Joshua L.; Cloutis, Edward A.; Rice, Melissa S. (2013-04-01). "Hydrated silica on Mars: Combined analysis with near-infrared and thermal-infrared spectroscopy". Icarus. 223 (2): 633–648. Bibcode:2013Icar..223..633S. doi:10.1016/j.icarus.2013.01.024. ISSN 0019-1035. <a href="https://www.sciencedirect.com/science/article/pii/S0019103513000390" target="_blank">https://www.sciencedirect.com/science/article/pii/S0019103513000390</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></li>
<li id="fn:7">"Hydrated Silica - an overview | ScienceDirect Topics". www.sciencedirect.com. Retrieved 2023-02-04. <a href="https://www.sciencedirect.com/topics/chemistry/hydrated-silica" target="_blank">https://www.sciencedirect.com/topics/chemistry/hydrated-silica</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></li>
<li id="fn:8">Smith, Matthew R.; Bandfield, Joshua L.; Cloutis, Edward A.; Rice, Melissa S. (2013-04-01). "Hydrated silica on Mars: Combined analysis with near-infrared and thermal-infrared spectroscopy". Icarus. 223 (2): 633–648. Bibcode:2013Icar..223..633S. doi:10.1016/j.icarus.2013.01.024. ISSN 0019-1035. <a href="https://www.sciencedirect.com/science/article/pii/S0019103513000390" target="_blank">https://www.sciencedirect.com/science/article/pii/S0019103513000390</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></li>
<li id="fn:9">Smith, Matthew R.; Bandfield, Joshua L.; Cloutis, Edward A.; Rice, Melissa S. (2013-04-01). "Hydrated silica on Mars: Combined analysis with near-infrared and thermal-infrared spectroscopy". Icarus. 223 (2): 633–648. Bibcode:2013Icar..223..633S. doi:10.1016/j.icarus.2013.01.024. ISSN 0019-1035. <a href="https://www.sciencedirect.com/science/article/pii/S0019103513000390" target="_blank">https://www.sciencedirect.com/science/article/pii/S0019103513000390</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></li>
<li id="fn:10">Smith, Matthew R.; Bandfield, Joshua L.; Cloutis, Edward A.; Rice, Melissa S. (2013-04-01). "Hydrated silica on Mars: Combined analysis with near-infrared and thermal-infrared spectroscopy". Icarus. 223 (2): 633–648. Bibcode:2013Icar..223..633S. doi:10.1016/j.icarus.2013.01.024. ISSN 0019-1035. <a href="https://www.sciencedirect.com/science/article/pii/S0019103513000390" target="_blank">https://www.sciencedirect.com/science/article/pii/S0019103513000390</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></li>
<li id="fn:11">Zhang, Sheng; Tang, Wufei; Guo, Jia; Jin, Xiaodong; Li, Hongfei; Gu, Xiaoyu; Sun, Jun (2018-08-01). "Improvement of flame retardancy and thermal stability of polypropylene by P-type hydrated silica aluminate containing lanthanum". Polymer Degradation and Stability. 154: 276–284. doi:10.1016/j.polymdegradstab.2018.06.014. ISSN 0141-3910. S2CID 139985716. <a href="https://www.sciencedirect.com/science/article/pii/S0141391018302064" target="_blank">https://www.sciencedirect.com/science/article/pii/S0141391018302064</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></li>
<li id="fn:12">Fire retardancy of polymeric materials. Arthur F. Grand, Charles A. Wilkie. New York: Marcel Dekker. 2000. ISBN 0-8247-8879-6. OCLC 43569399.{{cite book}}: CS1 maint: others (link) <a href="0-8247-8879-6" target="_blank">0-8247-8879-6</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></li>
<li id="fn:13">https://web.archive.org/web/20071126082443/http://www.tomsofmaine.com/toms/ifs/hydrated_silica.asp [bare URL] <a href="https://web.archive.org/web/20071126082443/http://www.tomsofmaine.com/toms/ifs/hydrated_silica.asp" target="_blank">https://web.archive.org/web/20071126082443/http://www.tomsofmaine.com/toms/ifs/hydrated_silica.asp</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></li>
</ol>

Hydrated silica open-in-new

Hydrated silica