Editing Sulfur (section)

===Allotropes===
{{Main|Allotropes of sulfur}}
[[File:Cyclooctasulfur-above-3D-balls.png|thumb|left|The structure of the cyclooctasulfur molecule, S<sub>8</sub>]]
Sulfur forms over 30 solid [[allotropy|allotropes]], more than any other element.<ref>{{cite book |title= Solid Sulfur Allotropes Sulfur Allotropes |first1= Ralf |last1= Steudel|first2= Bodo|last2= Eckert|date= 2003 |volume= 230 |pages= 1–80 |doi= 10.1007/b12110 |series= Topics in Current Chemistry |isbn= 978-3-540-40191-9}}</ref> Besides S<sub>8</sub>, several other rings are known.<ref>{{cite book |doi=10.1007/3-540-11345-2_10 |last= Steudel|first= R. |date= 1982 |volume= 102 |pages= 149–176 |series=Topics in Current Chemistry |isbn=978-3-540-11345-4|title= Inorganic Ring Systems|chapter= Homocyclic sulfur molecules}}</ref> Removing one atom from the crown gives S<sub>7</sub>, which is of a deeper yellow than S<sub>8</sub>. [[High-performance liquid chromatography|HPLC]] analysis of "elemental sulfur" reveals an equilibrium mixture of mainly S<sub>8</sub>, but with S<sub>7</sub> and small amounts of S<sub>6</sub>.<ref>{{cite journal |last1= Tebbe |first1= Fred N. |last2= Wasserman |first2= E. |last3= Peet |first3= William G. |last4= Vatvars |first4= Arturs |last5= Hayman |first5= Alan C. |title= Composition of Elemental Sulfur in Solution: Equilibrium of {{chem|S|6}}, S<sub>7</sub>, and S<sub>8</sub> at Ambient Temperatures |journal= Journal of the American Chemical Society|date= 1982 |volume= 104 |issue= 18 |pages= 4971–4972 |doi= 10.1021/ja00382a050|bibcode= 1982JAChS.104.4971T }}</ref> Larger rings have been prepared, including S<sub>12</sub> and S<sub>18</sub>.<ref>{{cite journal|last1= Meyer|first1= Beat|title= Solid Allotropes of Sulfur|journal= Chemical Reviews |date= 1964|volume= 64|issue= 4|pages= 429–451|doi= 10.1021/cr60230a004}}</ref><ref>{{cite journal|last1= Meyer|first1= Beat|title= Elemental sulfur|journal= Chemical Reviews|date= 1976|volume= 76|issue= 3|pages= 367–388 |doi= 10.1021/cr60301a003}}</ref>

[[Amorphous]] or "plastic" sulfur is produced by rapid cooling of molten sulfur—for example, by pouring it into cold water. [[X-ray crystallography]] studies show that the amorphous form may have a [[helix|helical]] structure with eight atoms per turn. The long coiled polymeric molecules make the brownish substance [[elasticity (physics)|elastic]], and in bulk it has the feel of crude rubber. This form is [[metastability in molecules|metastable]] at room temperature and gradually reverts to the crystalline molecular allotrope, which is no longer elastic. This process happens over a matter of hours to days, but can be rapidly catalyzed.
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