Editing Sulfur (section)

===Physical properties===
[[File:Burning-sulfur.png|thumb|upright|left|As a solid, sulfur is a characteristic lemon yellow; when burned, sulfur melts into a blood-red liquid and emits a blue flame.]]

Sulfur forms several polyatomic molecules. The best-known allotrope is [[octasulfur]], cyclo-S<sub>8</sub>. The [[point group]] of cyclo-S<sub>8</sub> is D<sub>4d</sub> and its dipole moment is 0 D.<ref>{{cite journal|last1=Rettig|first1=S. J. |last2=Trotter |first2=J. |title=Refinement of the structure of orthorhombic sulfur, α-S8 |journal=Acta Crystallographica Section C|date=15 December 1987 |volume=43 |issue=12 |pages=2260–2262 |doi=10.1107/S0108270187088152 |bibcode=1987AcCrC..43.2260R |url=http://journals.iucr.org/c/issues/1987/12/00/a27614/a27614.pdf|issn = 0108-2701 }}</ref> Octasulfur is a soft, bright-yellow solid that is odorless.{{efn|But impure samples have an odor similar to that of [[match]]es. A strong odor called "smell of sulfur" actually is given off by several sulfur compounds, such as [[hydrogen sulfide]] and [[organosulfur]] compounds.}} It melts at {{convert|115.21|C}},{{efn|Sulfur's melting point at 115.21°C was determined by two laboratories of the US Department of Energy (Jefferson Lab and Los Alamos National Lab).<ref>{{Cite web |title=Sulfur {{!}} S (Element) - PubChem |url=https://pubchem.ncbi.nlm.nih.gov/element/Sulfur |access-date=2024-04-15 |website=pubchem.ncbi.nlm.nih.gov}}</ref>
Greenwood and Earnshaw say that at fast heating for microcrystalline α-S<sub>8</sub> the melting point is {{convert|115.1|C}}.<ref name="Greenwood-1997a" />}} and boils at {{convert|444.6|C}}.<ref name="Greenwood-1997a" /> At {{convert|95.2|C}}, below its melting temperature, cyclo-octasulfur begins slowly changing from α-octasulfur to the β-[[polymorphism (materials science)|polymorph]].<ref name="Greenwood-1997b">{{Greenwood&Earnshaw2nd|pages= 645–665}}</ref> The structure of the S<sub>8</sub> ring is virtually unchanged by this phase transition, which affects the intermolecular interactions. Cooling molten sulfur freezes at {{convert|119.6|C}},<ref>{{Cite book |last1=Poling |first1=Bruce E. |url=https://books.google.com/books?id=9tGclC3ZRX0C |title=The Properties of Gases and Liquids 5E |last2=Prausnitz |first2=John M. |last3=O'Connell |first3=John P. |date=2000-11-27 |publisher=McGraw Hill Professional |isbn=978-0-07-149999-6 |language=en}}</ref> as it predominantly consists of the β-S<sub>8</sub> molecules.{{efn|Historically, it was rather difficult to find the exact melting point of sulfur.<ref>{{Cite web |date=2013-10-03 |title=7.5: Changes of State |url=https://chem.libretexts.org/Bookshelves/General_Chemistry/Chem1_(Lower)/07%3A_Solids_and_Liquids/7.05%3A_Changes_of_State |access-date=2024-04-15 |website=Chemistry LibreTexts |language=en}}</ref> When heated slowly, the melting point may range from {{convert|114.6|C}} to {{convert|120.4|C}}<ref name="Greenwood-1997a" /> (factors that interfere with a definite melting point, are the [[Crystallization of polymers|polymerlike nature]] of sulfur<ref>{{Cite journal |last1=Kozhevnikov |first1=V. F. |last2=Payne |first2=W. B. |last3=Olson |first3=J. K. |last4=McDonald |first4=C. L. |last5=Inglefield |first5=C. E. |date=2004-10-15 |title=Physical properties of sulfur near the polymerization transition |url=https://pubmed.ncbi.nlm.nih.gov/15473808/ |journal=The Journal of Chemical Physics |volume=121 |issue=15 |pages=7379–7386 |doi=10.1063/1.1794031 |issn=0021-9606 |pmid=15473808|arxiv=physics/0405012 |bibcode=2004JChPh.121.7379K }}</ref> and a large number of allotropes.<ref>{{Cite journal |last1=Inostroza |first1=Manuel |last2=Fernandez |first2=Bárbara |last3=Aguilera |first3=Felipe |last4=Layana |first4=Susana |last5=Walter |first5=Thomas R. |last6=Zimmer |first6=Martin |last7=Rodríguez-Díaz |first7=Augusto |last8=Oelze |first8=Marcus |date=2023 |title=Physical and chemical characteristics of active sulfur flows observed at Lastarria volcano (northern Chile) in January 2019 |journal=Frontiers in Earth Science |volume=11 |doi=10.3389/feart.2023.1197363 |doi-access=free |bibcode=2023FrEaS..1197363I |issn=2296-6463}}</ref>) Melting point may be presented as a temperature range, depending on the allotropic composition of a sample at the time of melting.}} Between its melting and boiling temperatures, octasulfur changes its allotrope again, turning from β-octasulfur to γ-sulfur, again accompanied by a lower density but increased [[viscosity]] due to the formation of [[polymer]]s.<ref name="Greenwood-1997b" /> At higher temperatures, the viscosity decreases as depolymerization occurs. Molten sulfur assumes a dark red color above {{convert|200|C}}. The density of sulfur is about 2&nbsp;g/cm<sup>3</sup>, depending on the allotrope; all of the stable allotropes are excellent electrical insulators.

Sulfur [[Sublimation (phase transition)|sublimes]] more or less between {{convert|20|C}} and {{convert|50|C}}.<ref>{{Cite journal |last=Tucker |first=Roy P. |date=1929-01-01 |title=Notes on the Sublimation of Sulfur between 25° and 50°C |url=https://pubs.acs.org/doi/abs/10.1021/ie50229a014 |journal=Industrial & Engineering Chemistry |language=en |volume=21 |issue=1 |pages=44–47 |doi=10.1021/ie50229a014 |issn=0019-7866}}</ref>

Sulfur is insoluble in water but soluble in [[carbon disulfide]] and, to a lesser extent, in other [[Chemical polarity|nonpolar]] organic solvents, such as [[benzene]] and [[toluene]].