Editing Silicate (section)

==Chemical properties==
<!--Solid silicates are generally stable and well characterized.-->

Silicates with [[alkali]] cations and small or chain-like anions, such as [[sodium orthosilicate|sodium ortho-]] and [[sodium metasilicate|metasilicate]], are fairly soluble in water.  They form several solid [[hydrate]]s when crystallized from solution.  Soluble [[sodium silicate]]s and mixtures thereof, known as [[waterglass]] are important industrial and household chemicals. Silicates of non-alkali cations, or with sheet and tridimensional polymeric anions, generally have negligible solubility in water at normal conditions.

===Reactions===
{{Biomineralization sidebar|geologic forms}}
Silicates are generally inert chemically.  Hence they are common minerals. Their resiliency also recommends their use as building materials.

When treated with calcium oxides and water, silicate minerals form [[Portland cement]].

Equilibria involving hydrolysis of silicate minerals are difficult to study. The chief challenge is the very low solubility of SiO<sub>4</sub><sup>4-</sup> and its various protonated forms. Such equilibria are relevant to the processes occurring on geological time scales.<ref name=knight/><ref name=GBAlex>G. B. Alexander (1953): "The Reaction of Low Molecular Weight Silicic Acids with Molybdic Acid". ''Journal of the American Chemical Society, volume 75, issue 22, pages 5655–5657. {{doi|10.1021/ja01118a054}}</ref>  Some plants excrete ligands that dissolve silicates, a step in [[biomineralization]].

Catechols can depolymerize SiO₂—a component of silicates with ionic structures like orthosilicate (SiO₄⁴⁻), metasilicate (SiO₂³⁻), and pyrosilicate (Si₂O₆⁷⁻)—by forming bis- and tris(catecholate)silicate dianions through coordination.<ref>{{Cite journal |last=Mazaheri |first=Omid |date=14 November 2024 |title=Assembly of Silicate–Phenolic Network Coatings with Tunable Properties for Controlled Release of Small Molecules |url=https://onlinelibrary.wiley.com/doi/full/10.1002/adma.202413349 |journal=Advanced Materials |doi=10.1002/adma.202413349|url-access=subscription }}</ref> This complexes can be further coated on various substrates for applications such as drug delivery systems, antibacterial and antifouling applications.

===Detection===
Silicate anions in solution react with [[molybdate]] anions yielding yellow [[silicomolybdate]] complexes. In a typical preparation, [[monomer]]ic orthosilicate was found to react completely in 75 seconds; [[dimer (chemistry)|dimer]]ic pyrosilicate in 10 minutes; and higher [[oligomer]]s in considerably longer time.  In particular, the reaction is not observed with suspensions of [[colloidal silica]].<ref name=GBAlex/>

===Zeolite formation and geopolymers polymerisation===
The nature of soluble silicates is relevant to understanding [[biomineralization]] and the synthesis of [[aluminosilicate]]s, such as the industrially important [[catalyst]]s called [[zeolite]]s.<ref name=knight>{{cite journal | last1 = Knight | first1 = Christopher T. G. | last2 = Balec | first2 = Raymond J. | last3 = Kinrade | first3 = Stephen D. | year = 2007 | title = The Structure of Silicate Anions in Aqueous Alkaline Solutions | journal = Angewandte Chemie International Edition | volume = 46 | issue = 43 | pages = 8148–8152 | doi = 10.1002/anie.200702986 | pmid = 17886822 }}</ref> Along with [[aluminate]] [[anion]]s, soluble silicate anions also play a major role in the polymerization mechanism of [[geopolymer]]s. Geopolymers are [[amorphous]] aluminosilicates whose production requires less energy than that of ordinary [[Portland cement]]. So, [[geopolymer cement]]s could contribute to limiting the {{CO2|link=carbon dioxide}} emissions in the Earth [[atmosphere]] and the [[global warming]] caused by this [[greenhouse gas]].