Sulfur

<h2 id="characteristics">Characteristics</h2>
<h3>Physical properties</h3>

Sulfur forms several polyatomic molecules. The best-known allotrope is <a href="/facts/Octasulfur/sub03Upn">octasulfur</a>, cyclo-S8. The <a href="/facts/Point_group/41NSqUN6">point group</a> of cyclo-S8 is D4d and its dipole moment is 0 D.<a class="footnote-ref" id="fnref:6" href="#fn:6">6</a> Octasulfur is a soft, bright-yellow solid that is odorless.<a class="footnote-ref" id="fnref:7" href="#fn:7">7</a> It melts at 115.21 °C (239.38 °F),<a class="footnote-ref" id="fnref:8" href="#fn:8">8</a> and boils at 444.6 °C (832.3 °F).<a class="footnote-ref" id="fnref:9" href="#fn:9">9</a> At 95.2 °C (203.4 °F), below its melting temperature, cyclo-octasulfur begins slowly changing from α-octasulfur to the β-<a href="/facts/Polymorphism_(materials_science)/bu2tqsB9">polymorph</a>.<a class="footnote-ref" id="fnref:10" href="#fn:10">10</a> The structure of the S8 ring is virtually unchanged by this phase transition, which affects the intermolecular interactions. Cooling molten sulfur freezes at 119.6 °C (247.3 °F),<a class="footnote-ref" id="fnref:11" href="#fn:11">11</a> as it predominantly consists of the β-S8 molecules.<a class="footnote-ref" id="fnref:12" href="#fn:12">12</a> 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 <a href="/facts/Viscosity/QLVfrdCz">viscosity</a> due to the formation of <a href="/facts/Polymer/eF32E50K">polymers</a>.<a class="footnote-ref" id="fnref:13" href="#fn:13">13</a> At higher temperatures, the viscosity decreases as depolymerization occurs. Molten sulfur assumes a dark red color above 200 °C (392 °F). The density of sulfur is about 2 g/cm3, depending on the allotrope; all of the stable allotropes are excellent electrical insulators.
The <a href="/facts/Sublimation_(phase_transition)/KDoKokMn">sublimation</a> of sulfur becomes noticeable more or less between 20 °C (68 °F) and 50 °C (122 °F), and occurs readily in boiling water at 100 °C (212 °F).<a class="footnote-ref" id="fnref:14" href="#fn:14">14</a>
Sulfur is insoluble in water but soluble in <a href="/facts/Carbon_disulfide/b04Tadmy">carbon disulfide</a> and, to a lesser extent, in other <a href="/facts/Chemical_polarity/KlIJ0zjB">nonpolar</a> organic solvents, such as <a href="/facts/Benzene/Fguue7nr">benzene</a> and <a href="/facts/Toluene/Pzdt8dwD">toluene</a>.

<h3>Chemical properties</h3>
Under normal conditions, sulfur <a href="/facts/Hydrolysis/JTvwIHPs">hydrolyzes</a> very slowly to mainly form <a href="/facts/Hydrogen_sulfide/UbCqjMMk">hydrogen sulfide</a> and <a href="/facts/Sulfuric_acid/Wom6fymJ">sulfuric acid</a>:

1⁄2 S8 + 4 H2O → 3 H2S + H2SO4

The reaction involves adsorption of protons onto S8 clusters, followed by <a href="/facts/Disproportionation/67QMkXrV">disproportionation</a> into the reaction products.<a class="footnote-ref" id="fnref:15" href="#fn:15">15</a>
The second, fourth and sixth <a href="/facts/Molar_ionization_energies_of_the_elements/B7PHRcws">ionization energies</a> of sulfur are 2252 kJ/mol, 4556 kJ/mol and 8495.8 kJ/mol, respectively. The composition of reaction products of sulfur with oxidants (and its oxidation state) depends on whether releasing of reaction energy overcomes these thresholds. Applying <a href="/facts/Catalysis/LPBS7TQC">catalysts</a> and/or <a href="/facts/Endothermic_process/06xmHw6Q">supply of external energy</a> may vary sulfur's oxidation state and the composition of reaction products. While reaction between sulfur and oxygen under normal conditions gives sulfur dioxide (oxidation state +4), formation of <a href="/facts/Sulfur_trioxide/Ijvm08Lq">sulfur trioxide</a> (oxidation state +6) requires a temperature of 400–600 °C (750–1,100 °F) and presence of a catalyst.
In reactions with elements of lesser <a href="/facts/Electronegativity/H7Vq7Uah">electronegativity</a>, it reacts as an oxidant and forms sulfides, where it has oxidation state −2.
Sulfur reacts with nearly all other elements except noble gases, even with the notoriously unreactive metal <a href="/facts/Iridium/cB4n6MbQ">iridium</a> (yielding <a href="/facts/Iridium_disulfide/ChIFotwr">iridium disulfide</a>).<a class="footnote-ref" id="fnref:16" href="#fn:16">16</a> Some of those reactions require elevated temperatures.<a class="footnote-ref" id="fnref:17" href="#fn:17">17</a>

<h3>Allotropes</h3>
Main article: <a href="/facts/Allotropes_of_sulfur/b1TUYVFQ">Allotropes of sulfur</a>

Sulfur forms over 30 solid <a href="/facts/Allotropy/2WUdHWxg">allotropes</a>, more than any other element.<a class="footnote-ref" id="fnref:18" href="#fn:18">18</a> Besides S8, several other rings are known.<a class="footnote-ref" id="fnref:19" href="#fn:19">19</a> Removing one atom from the crown gives S7, which is of a deeper yellow than S8. <a href="/facts/High-performance_liquid_chromatography/UNT9jPp0">HPLC</a> analysis of "elemental sulfur" reveals an equilibrium mixture of mainly S8, but with S7 and small amounts of S6.<a class="footnote-ref" id="fnref:20" href="#fn:20">20</a> Larger rings have been prepared, including S12 and S18.<a class="footnote-ref" id="fnref:21" href="#fn:21">21</a><a class="footnote-ref" id="fnref:22" href="#fn:22">22</a>
<a href="/facts/Amorphous/YTIzmrR0">Amorphous</a> or "plastic" sulfur is produced by rapid cooling of molten sulfur—for example, by pouring it into cold water. <a href="/facts/X-ray_crystallography/WtI0F5DN">X-ray crystallography</a> studies show that the amorphous form may have a <a href="/facts/Helix/BqC4AKwL">helical</a> structure with eight atoms per turn. The long coiled polymeric molecules make the brownish substance <a href="/facts/Elasticity_(physics)/wcJoIFg1">elastic</a>, and in bulk it has the feel of crude rubber. This form is <a href="/facts/Metastability_in_molecules/H72SMWof">metastable</a> 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.

<h3>Isotopes</h3>
Main article: <a href="/facts/Isotopes_of_sulfur/08Qs8w3o">Isotopes of sulfur</a>
Sulfur has 23 known <a href="/facts/Isotope/KD9B1y6o">isotopes</a>, four of which are stable: 32S (94.99%±0.26%), 33S (0.75%±0.02%), 34S (4.25%±0.24%), and 36S (0.01%±0.01%).<a class="footnote-ref" id="fnref:23" href="#fn:23">23</a><a class="footnote-ref" id="fnref:24" href="#fn:24">24</a> Other than 35S, with a <a href="/facts/Half-life/kGVH8BAB">half-life</a> of 87 days, the <a href="/facts/Radioactivity/Ya6FVjt4">radioactive</a> isotopes of sulfur have half-lives less than 3 hours.
The preponderance of 32S is explained by its production in the so-called alpha-process (one of the main classes of nuclear fusion reactions) in exploding stars. Other stable sulfur isotopes are produced in the bypass processes related with 34Ar, and their composition depends on a type of a stellar explosion. For example, proportionally more 33S comes from <a href="/facts/Novae/H1GcmKXT">novae</a> than from <a href="/facts/Supernovae/Pfo2J23l">supernovae</a>.<a class="footnote-ref" id="fnref:25" href="#fn:25">25</a>
On the planet Earth the sulfur isotopic composition was determined by the Sun. Though it was assumed that the distribution of different sulfur isotopes would be more or less equal, it has been found that proportions of the two most abundant sulfur isotopes 32S and 34S varies in different samples. Assaying of the isotope ratio (<a href="/facts/%25CE%259434S/T67cbdg4">δ34S</a>) in the samples suggests their chemical history, and with support of other methods, it allows to age-date the samples, estimate temperature of equilibrium between ore and water, determine pH and oxygen <a href="/facts/Fugacity/C2gdkThT">fugacity</a>, identify the activity of sulfate-reducing bacteria in the time of formation of the sample, or suggest the main sources of sulfur in ecosystems.<a class="footnote-ref" id="fnref:26" href="#fn:26">26</a> However, there are ongoing discussions over the real reason for the δ34S shifts, biological activity or postdeposit alteration.<a class="footnote-ref" id="fnref:27" href="#fn:27">27</a>
For example, when <a href="/facts/Sulfide_mineral/f8rxJpCW">sulfide minerals</a> are precipitated, isotopic equilibration among solids and liquid may cause small differences in the δ34S values of co-genetic minerals. The differences between minerals can be used to estimate the temperature of equilibration. The <a href="/facts/%25CE%259413C/mMh14cU1">δ13C</a> and δ34S of coexisting <a href="/facts/Carbonate_minerals/8DUmuAhp">carbonate minerals</a> and sulfides can be used to determine the <a href="/facts/PH/RnSv8D7y">pH</a> and oxygen fugacity of the ore-bearing fluid during ore formation.
Scientists measure the <a href="/facts/Sulfur_isotope_biogeochemistry/98zskyIs">sulfur isotopes</a> of <a href="/facts/Mineral/LkUFbNmv">minerals</a> in rocks and <a href="/facts/Sediment/zsIH1A6U">sediments</a> to study the <a href="/facts/Redox/Pyd5RVcj">redox</a> conditions in past oceans. <a href="/facts/Sulfate-reducing_microorganism/uvFQhLWe">Sulfate-reducing bacteria</a> in marine sediment fractionate <a href="/facts/Sulfur_isotope_biogeochemistry/98zskyIs">sulfur isotopes</a> as they take in <a href="/facts/Sulfate/yuWVxsUf">sulfate</a> and produce <a href="/facts/Sulfide/d8YMjLeu">sulfide</a>. Prior to the 2010s, it was thought that sulfate reduction could fractionate <a href="/facts/Sulfur_isotope_biogeochemistry/98zskyIs">sulfur isotopes</a> up to 46 <a href="/facts/Permil/3xNDvE9l">permil</a><a class="footnote-ref" id="fnref:28" href="#fn:28">28</a> and fractionation larger than 46 permil recorded in sediments must be due to <a href="/facts/Disproportionation/67QMkXrV">disproportionation</a> of sulfur compounds in the sediment. This view has changed since the 2010s as experiments showed that <a href="/facts/Sulfate-reducing_microorganism/uvFQhLWe">sulfate-reducing bacteria</a> can fractionate to 66 permil.<a class="footnote-ref" id="fnref:29" href="#fn:29">29</a> As substrates for disproportionation are limited by the product of <a href="/facts/Sulfate-reducing_microorganism/uvFQhLWe">sulfate reduction</a>, the isotopic effect of disproportionation should be less than 16 permil in most sedimentary settings.<a class="footnote-ref" id="fnref:30" href="#fn:30">30</a>
In <a href="/facts/Forest/RnMtb31v">forest</a> ecosystems, sulfate is derived mostly from the atmosphere; weathering of ore minerals and evaporites contribute some sulfur. Sulfur with a distinctive isotopic composition has been used to identify pollution sources, and enriched sulfur has been added as a tracer in <a href="/facts/Hydrology/Xh727cnE">hydrologic</a> studies. Differences in the <a href="/facts/Natural_abundance/dGjaAwc9">natural abundances</a> can be used in systems where there is sufficient variation in the 34S of ecosystem components. <a href="/facts/Rocky_Mountain/rDc3cU0E">Rocky Mountain</a> lakes thought to be dominated by atmospheric sources of sulfate have been found to have measurably different 34S values than lakes believed to be dominated by watershed sources of sulfate.
The radioactive 35S is formed in <a href="/facts/Cosmic_ray_spallation/gSlq9VEP">cosmic ray spallation</a> of the atmospheric <a href="/facts/Argon-40/BhxtyJGu">40Ar</a>. This fact may be used to verify the presence of recent (up to 1 year) atmospheric sediments in various materials. This isotope may be obtained artificially by different ways. In practice, the reaction <a href="/facts/Chlorine-35/fdtzH9YF">35Cl</a> + <a href="/facts/Neutron/oRCM1geb">n</a> → 35S + <a href="/facts/Proton/clCjepXP">p</a> is used by irradiating <a href="/facts/Potassium_chloride/RgT2MdPa">potassium chloride</a> with neutrons.<a class="footnote-ref" id="fnref:31" href="#fn:31">31</a> The isotope 35S is used in various sulfur-containing compounds as a <a href="/facts/Radioactive_tracer/0210Jncn">radioactive tracer</a> for many biological studies, for example, the <a href="/facts/Hershey-Chase_experiment/kJJpIHIE">Hershey-Chase experiment</a>.
Because of the weak <a href="/facts/Beta_decay/vxTBlckp">beta activity</a> of 35S, its compounds are relatively safe as long as they are not ingested or absorbed by the body.<a class="footnote-ref" id="fnref:32" href="#fn:32">32</a>

<h3>Natural occurrence</h3>

32S is created inside massive stars, at a depth where the temperature exceeds 2.5×109 K, by the <a href="/facts/Silicon_burning/qpYtHo8c">fusion</a> of one nucleus of silicon plus one nucleus of helium.<a class="footnote-ref" id="fnref:33" href="#fn:33">33</a> As this nuclear reaction is part of the <a href="/facts/Alpha_process/S8cf71rL">alpha process</a> that produces elements in abundance, sulfur is the 10th <a href="/facts/Abundance_of_the_chemical_elements/CE9WehBl">most common element in the universe</a>.
Sulfur, usually as sulfide, is present in many types of <a href="/facts/Meteorite/NsmHlBlX">meteorites</a>. <a href="/facts/Ordinary_chondrite/9dysJBuy">Ordinary chondrites</a> contain on average 2.1% sulfur, and <a href="/facts/Carbonaceous_chondrite/TnCY8ssz">carbonaceous chondrites</a> may contain as much as 6.6%. It is normally present as <a href="/facts/Troilite/tWP2rSj1">troilite</a> (FeS), but there are exceptions, with carbonaceous chondrites containing free sulfur, sulfates and other sulfur compounds.<a class="footnote-ref" id="fnref:34" href="#fn:34">34</a> The distinctive colors of <a href="/facts/Jupiter/95m7XjMT">Jupiter</a>'s <a href="/facts/Volcano/c2M5upml">volcanic</a> moon <a href="/facts/Io_(moon)/p3Uc8FmK">Io</a> are attributed to various forms of molten, solid, and gaseous sulfur.<a class="footnote-ref" id="fnref:35" href="#fn:35">35</a> In July 2024, elemental sulfur was accidentally discovered to exist on <a href="/facts/Mars/AQGtVvz0">Mars</a> after the <a href="/facts/Curiosity_(rover)/mVLawAfA">Curiosity rover</a> drove over and crushed a rock, revealing sulfur crystals inside it.<a class="footnote-ref" id="fnref:36" href="#fn:36">36</a>
Sulfur is the fifth most common element by mass in the Earth. Elemental sulfur can be found near <a href="/facts/Hot_spring/YrzFykH1">hot springs</a> and <a href="/facts/Volcanic/c2M5upml">volcanic</a> regions in many parts of the world, especially along the <a href="/facts/Pacific_Ring_of_Fire/UpRWnP2P">Pacific Ring of Fire</a>; such volcanic deposits are mined in Indonesia, Chile, and Japan. These deposits are polycrystalline, with the largest documented single crystal measuring 22 cm × 16 cm × 11 cm (8.7 in × 6.3 in × 4.3 in).<a class="footnote-ref" id="fnref:37" href="#fn:37">37</a> Historically, <a href="/facts/Sicily/E6fug03z">Sicily</a> was a major source of sulfur in the <a href="/facts/Industrial_Revolution/B6E3Fasm">Industrial Revolution</a>.<a class="footnote-ref" id="fnref:38" href="#fn:38">38</a> Lakes of molten sulfur up to about 200 m (660 ft) in diameter have been found on the sea floor, associated with <a href="/facts/Submarine_volcano/HD4HjUgb">submarine volcanoes</a>, at depths where the boiling point of water is higher than the melting point of sulfur.<a class="footnote-ref" id="fnref:39" href="#fn:39">39</a>
Native sulfur is synthesized by <a href="/facts/Anaerobic_bacteria/bhQnlqCq">anaerobic bacteria</a> acting on <a href="/facts/Sulfate_minerals/AQAw1nJg">sulfate minerals</a> such as <a href="/facts/Gypsum/MItYU70n">gypsum</a> in <a href="/facts/Salt_dome/RsPm1A8y">salt domes</a>.<a class="footnote-ref" id="fnref:40" href="#fn:40">40</a><a class="footnote-ref" id="fnref:41" href="#fn:41">41</a> Significant deposits in salt domes occur along the coast of the <a href="/facts/Gulf_of_Mexico/bGE5s57G">Gulf of Mexico</a>, and in <a href="/facts/Evaporite/vNW8fcEy">evaporites</a> in eastern Europe and western Asia. Native sulfur may be produced by geological processes alone. Fossil-based sulfur deposits from salt domes were once the basis for commercial production in the United States, Russia, Turkmenistan, and Ukraine.<a class="footnote-ref" id="fnref:42" href="#fn:42">42</a> Such sources have become of secondary commercial importance, and most are no longer worked but commercial production is still carried out in the <a href="/facts/Osiek%2c_%25C5%259Awi%25C4%2599tokrzyskie_Voivodeship/9w3nuycA">Osiek</a> mine in Poland.
Common naturally occurring sulfur compounds include the <a href="/facts/Mineral/LkUFbNmv">sulfide minerals</a>, such as <a href="/facts/Pyrite/41CYREyr">pyrite</a> (iron sulfide), <a href="/facts/Cinnabar/MUzsHjFw">cinnabar</a> (mercury sulfide), <a href="/facts/Galena/eSaK62FA">galena</a> (lead sulfide), <a href="/facts/Sphalerite/5NumvnzR">sphalerite</a> (zinc sulfide), and <a href="/facts/Stibnite/f1wo26vQ">stibnite</a> (antimony sulfide); and the <a href="/facts/Mineral/LkUFbNmv">sulfate minerals</a>, such as <a href="/facts/Gypsum/MItYU70n">gypsum</a> (calcium sulfate), <a href="/facts/Alunite/UXHTTDq0">alunite</a> (potassium aluminium sulfate), and <a href="/facts/Barite/G6frVDl5">barite</a> (barium sulfate). On Earth, just as upon Jupiter's moon Io, elemental sulfur occurs naturally in volcanic emissions, including emissions from <a href="/facts/Hydrothermal_vent/0xPqNUkY">hydrothermal vents</a>.
The main industrial source of sulfur has become <a href="/facts/Petroleum/IQV0bHVd">petroleum</a> and <a href="/facts/Natural_gas/9MYQ7NAP">natural gas</a>.<a class="footnote-ref" id="fnref:43" href="#fn:43">43</a>

<h2 id="compounds">Compounds</h2>
Main article: <a href="/facts/Sulfur_compounds/IK0amTfM">Sulfur compounds</a>
Common <a href="/facts/Oxidation_state/W53W6s6V">oxidation states</a> of sulfur range from −2 to +6. Sulfur forms stable compounds with all elements except the <a href="/facts/Noble_gas/j0yHMEAE">noble gases</a>.

<h3>Electron transfer reactions</h3>

Sulfur polycations, S2+8, S2+4 and S2+19 are produced when sulfur is reacted with oxidizing agents in a strongly acidic solution.<a class="footnote-ref" id="fnref:44" href="#fn:44">44</a> The colored solutions produced by dissolving sulfur in <a href="/facts/Oleum/oyT7XMod">oleum</a> were first reported as early as 1804 by C. F. Bucholz, but the cause of the color and the structure of the polycations involved was only determined in the late 1960s. S2+8 is deep blue, S2+4 is yellow and S2+19 is red.<a class="footnote-ref" id="fnref:45" href="#fn:45">45</a>
Reduction of sulfur gives various <a href="/facts/Polysulfide/PpfaUlw4">polysulfides</a> with the formula S2−x, many of which have been obtained in crystalline form. Illustrative is the production of <a href="/facts/Sodium_tetrasulfide/2CmWgJNg">sodium tetrasulfide</a>:

4 Na + S8 → 2 Na2S4
Some of these dianions dissociate to give <a href="/facts/Radical_anion/N4vFqKrV">radical anions</a>. For instance, <a href="/facts/Trisulfur/3jn3RdcG">S−3</a> gives the blue color of the rock <a href="/facts/Lapis_lazuli/KKPFyQFN">lapis lazuli</a>.

This reaction highlights a distinctive property of sulfur: its ability to <a href="/facts/Catenation/vm7k4zsv">catenate</a> (bind to itself by formation of chains). <a href="/facts/Protonation/q5Gf9z0M">Protonation</a> of these polysulfide anions produces the <a href="/facts/Polysulfane/FAGqzw4I">polysulfanes</a>, H2Sx, where x = 2, 3, and 4.<a class="footnote-ref" id="fnref:46" href="#fn:46">46</a> Ultimately, reduction of sulfur produces sulfide salts:

16 Na + S8 → 8 Na2S
The interconversion of these species is exploited in the <a href="/facts/Sodium%25E2%2580%2593sulfur_battery/anzLVAxD">sodium–sulfur battery</a>.

<h3>Hydrogenation</h3>
Treatment of sulfur with hydrogen gives <a href="/facts/Hydrogen_sulfide/UbCqjMMk">hydrogen sulfide</a>. When dissolved in water, hydrogen sulfide is mildly acidic:<a class="footnote-ref" id="fnref:47" href="#fn:47">47</a>

H2S ⇌ HS− + H+
Hydrogen sulfide gas and the hydrosulfide anion are extremely toxic to mammals, due to their inhibition of the oxygen-carrying capacity of <a href="/facts/Hemoglobin/RsD1MzYA">hemoglobin</a> and certain <a href="/facts/Cytochrome/VF51IeGv">cytochromes</a> in a manner analogous to <a href="/facts/Cyanide/t0o8FMKI">cyanide</a> and <a href="/facts/Azide/AaJwyv1z">azide</a> (see below, under precautions).

<h3>Combustion</h3>
The two principal sulfur oxides are obtained by burning sulfur:

S + O2 → SO2 (<a href="/facts/Sulfur_dioxide/jDK1fIDs">sulfur dioxide</a>)
2 SO2 + O2 → 2 SO3 (<a href="/facts/Sulfur_trioxide/Ijvm08Lq">sulfur trioxide</a>)
Many other sulfur oxides are observed including the <a href="/facts/Lower_sulfur_oxides/7ABYGhEB">sulfur-rich oxides</a> include <a href="/facts/Sulfur_monoxide/CI8PbSJX">sulfur monoxide</a>, <a href="/facts/Disulfur_monoxide/ez5v6KrH">disulfur monoxide</a>, disulfur dioxides, and <a href="/facts/Higher_sulfur_oxides/qTdYdmMR">higher oxides</a> containing peroxo groups.

<h3>Halogenation</h3>
Sulfur reacts with <a href="/facts/Fluorine/YUV0Fb8m">fluorine</a> to give the highly reactive <a href="/facts/Sulfur_tetrafluoride/jJYpjeSQ">sulfur tetrafluoride</a> and the highly inert <a href="/facts/Sulfur_hexafluoride/jeee0PJ8">sulfur hexafluoride</a>.<a class="footnote-ref" id="fnref:48" href="#fn:48">48</a> Whereas fluorine gives S(IV) and S(VI) compounds, chlorine gives S(II) and S(I) derivatives. Thus, <a href="/facts/Sulfur_dichloride/TTtzPjH4">sulfur dichloride</a>, <a href="/facts/Disulfur_dichloride/aYBYJprF">disulfur dichloride</a>, and higher chlorosulfanes arise from the chlorination of sulfur. <a href="/facts/Sulfuryl_chloride/UtEHXDb8">Sulfuryl chloride</a> and <a href="/facts/Chlorosulfuric_acid/L9pNz2P2">chlorosulfuric acid</a> are derivatives of sulfuric acid; <a href="/facts/Thionyl_chloride/nWwvNtvd">thionyl chloride</a> (SOCl2) is a common reagent in <a href="/facts/Organic_synthesis/WLFePEzH">organic synthesis</a>.<a class="footnote-ref" id="fnref:49" href="#fn:49">49</a> Bromine also oxidizes sulfur to form <a href="/facts/Sulfur_dibromide/pmfPGaeH">sulfur dibromide</a> and <a href="/facts/Disulfur_dibromide/xWNPlk48">disulfur dibromide</a>.<a class="footnote-ref" id="fnref:50" href="#fn:50">50</a>

<h3>Pseudohalides</h3>
Sulfur oxidizes <a href="/facts/Cyanide/t0o8FMKI">cyanide</a> and <a href="/facts/Sulfite/xdppUlKA">sulfite</a> to give <a href="/facts/Thiocyanate/S438CJp8">thiocyanate</a> and <a href="/facts/Thiosulfate/LYu0KhDu">thiosulfate</a>, respectively.

<h3>Metal sulfides</h3>
Sulfur reacts with many metals. Electropositive metals give polysulfide salts. Copper, zinc, and silver are attacked by sulfur; see <a href="/facts/Tarnishing/GCskvFrN">tarnishing</a>. Although many <a href="/facts/Sulfide_mineral/f8rxJpCW">metal sulfides</a> are known, most are prepared by high temperature reactions of the elements.<a class="footnote-ref" id="fnref:51" href="#fn:51">51</a> Geoscientists also study the isotopes of metal sulfides in rocks and sediment to study environmental conditions in the Earth's past.<a class="footnote-ref" id="fnref:52" href="#fn:52">52</a>

<h3>Organic compounds</h3>
Main article: <a href="/facts/Organosulfur_compounds/sUxSSXwD">Organosulfur compounds</a>

Some of the main classes of sulfur-containing organic compounds include the following:<a class="footnote-ref" id="fnref:53" href="#fn:53">53</a>

<ul><li><a href="/facts/Thiol/VemKEDP9">Thiols</a> or mercaptans (so called because they capture mercury as <a href="/facts/Chelation/4G79sXBB">chelators</a>) are the sulfur analogs of <a href="/facts/Alcohol_(chemistry)/Y0SCTDkh">alcohols</a>; treatment of thiols with base gives <a href="/facts/Thiolate/VemKEDP9">thiolate</a> ions.</li>
<li><a href="/facts/Thioether/GdyEz43f">Thioethers</a> are the sulfur analogs of <a href="/facts/Ether/jwDg0IKr">ethers</a>.</li>
<li><a href="/facts/Sulfonium/GcF77hXv">Sulfonium</a> ions have three groups attached to a cationic sulfur center. <a href="/facts/Dimethylsulfoniopropionate/5gUXrRQR">Dimethylsulfoniopropionate</a> (DMSP) is one such compound, important in the marine organic <a href="/facts/Sulfur_cycle/NzCakgxd">sulfur cycle</a>.</li>
<li><a href="/facts/Sulfoxide/Stk3Vnj9">Sulfoxides</a> and <a href="/facts/Sulfone/LJLP1RcT">sulfones</a> are thioethers with one and two oxygen atoms attached to the sulfur atom, respectively. The simplest sulfoxide, <a href="/facts/Dimethyl_sulfoxide/T4HSYfuC">dimethyl sulfoxide</a>, is a common solvent; a common sulfone is <a href="/facts/Sulfolane/oFKPToMK">sulfolane</a>.</li>
<li><a href="/facts/Sulfonic_acid/6JHPGnNY">Sulfonic acids</a> are used in many detergents.</li></ul>
Compounds with carbon–sulfur multiple bonds are uncommon, an exception being <a href="/facts/Carbon_disulfide/b04Tadmy">carbon disulfide</a>, a volatile colorless liquid that is structurally similar to carbon dioxide. It is used as a reagent to make the polymer <a href="/facts/Rayon/Us58BuEM">rayon</a> and many organosulfur compounds.<a class="footnote-ref" id="fnref:54" href="#fn:54">54</a> Unlike <a href="/facts/Carbon_monoxide/CKuLtEMJ">carbon monoxide</a>, <a href="/facts/Carbon_monosulfide/NmkhFybM">carbon monosulfide</a> is stable only as an extremely dilute gas, found between solar systems.<a class="footnote-ref" id="fnref:55" href="#fn:55">55</a>
Organosulfur compounds are responsible for some of the unpleasant odors of decaying organic matter. They are widely known as the <a href="/facts/Odorizer/BxTwHtKA">odorant</a> in domestic natural gas, garlic odor, and skunk spray, as well as a component of <a href="/facts/Bad_breath/8RGDp13v">bad breath</a> odor. Not all organic sulfur compounds smell unpleasant at all concentrations: the sulfur-containing <a href="/facts/Terpene/hDD4zF6P">monoterpenoid</a> <a href="/facts/Grapefruit_mercaptan/mJgMfTXl">grapefruit mercaptan</a> in small concentrations is the characteristic scent of grapefruit, but has a generic thiol odor at larger concentrations. <a href="/facts/Sulfur_mustard/e3qWU2Qp">Sulfur mustard</a>, a potent <a href="/facts/Blister_agent/5w33WIKa">vesicant</a>, was <a href="/facts/Chemical_weapons_in_World_War_I/s7HzwXTN">used in World War I</a> as a disabling agent.<a class="footnote-ref" id="fnref:56" href="#fn:56">56</a>
Sulfur–sulfur bonds are a structural component used to stiffen rubber, similar to the disulfide bridges that rigidify proteins (see biological below). In the most common type of industrial "curing" or hardening and strengthening of natural <a href="/facts/Rubber/CbsjJxhY">rubber</a>, elemental sulfur is heated with the rubber to the point that chemical reactions form <a href="/facts/Disulfide/eDx5Xtlg">disulfide</a> bridges between <a href="/facts/Isoprene/8ArKUyzT">isoprene</a> units of the polymer. This process, patented in 1843, made rubber a major industrial product, especially in automobile tires. Because of the heat and sulfur, the process was named <a href="/facts/Vulcanization/jmBUqGaz">vulcanization</a>, after the Roman god of the forge and <a href="/facts/Volcanism/0s6p1eFJ">volcanism</a>.

<h2 id="history">History</h2>
<h3>Antiquity</h3>

Being abundantly available in native form, sulfur was known in ancient times and is referred to in the <a href="/facts/Torah/BdJr9IFo">Torah</a>.<a class="footnote-ref" id="fnref:57" href="#fn:57">57</a> <a href="/facts/English_translations_of_the_Bible/5zf1bREm">English translations of the Christian Bible</a> commonly referred to burning sulfur as "brimstone", giving rise to the term "<a href="/facts/Fire_and_brimstone/jB5ykbFx">fire-and-brimstone</a>" <a href="/facts/Sermon/AT5m7TaU">sermons</a>, in which listeners are reminded of the fate of <a href="/facts/Damnation/67GhrmpG">eternal damnation</a> that await the unbelieving and unrepentant. It is from this part of the Bible<a class="footnote-ref" id="fnref:58" href="#fn:58">58</a> that <a href="/facts/Hell/2nIkoYTB">Hell</a> is implied to "smell of sulfur" (likely due to its association with volcanic activity). According to the <a href="/facts/Ebers_Papyrus/7KWeHwXs">Ebers Papyrus</a>, a sulfur ointment was used in ancient <a href="/facts/Egypt/8Ttg0JwB">Egypt</a> to treat granular eyelids. Sulfur was used for <a href="/facts/Fumigation/QGCodNPb">fumigation</a> in preclassical <a href="/facts/Greece/lqHw8bTB">Greece</a>;<a class="footnote-ref" id="fnref:59" href="#fn:59">59</a> this is mentioned in the <a href="/facts/Odyssey/tVTrA6nu">Odyssey</a>.<a class="footnote-ref" id="fnref:60" href="#fn:60">60</a> <a href="/facts/Pliny_the_Elder/grx67ghR">Pliny the Elder</a> discusses sulfur in book 35 of his <a href="/facts/Natural_History_(Pliny)/bMp2te1A">Natural History</a>, saying that its best-known source is the island of <a href="/facts/Melos/AY0u0GCz">Melos</a>. He mentions its use for fumigation, medicine, and bleaching cloth.<a class="footnote-ref" id="fnref:61" href="#fn:61">61</a>
A natural form of sulfur known as shiliuhuang (石硫黄) was known in China since the 6th century BC and found in <a href="/facts/Hanzhong/FY8dG24f">Hanzhong</a>.<a class="footnote-ref" id="fnref:62" href="#fn:62">62</a> By the 3rd century, the Chinese had discovered that sulfur could be extracted from <a href="/facts/Pyrite/41CYREyr">pyrite</a>.<a class="footnote-ref" id="fnref:63" href="#fn:63">63</a> Chinese <a href="/facts/Daoists/Bk79rd9J">Daoists</a> were interested in sulfur's flammability and its reactivity with certain metals, yet its earliest practical uses were found in <a href="/facts/Traditional_Chinese_medicine/51rSRXua">traditional Chinese medicine</a>.<a class="footnote-ref" id="fnref:64" href="#fn:64">64</a> The <a href="/facts/Wujing_Zongyao/SVYMpfF6">Wujing Zongyao</a> of 1044 AD described various formulas for Chinese <a href="/facts/Black_powder/AEcB6HCR">black powder</a>, which is a mixture of <a href="/facts/Potassium_nitrate/TycqMdcG">potassium nitrate</a> (KNO3), <a href="/facts/Charcoal/tpYGBHTn">charcoal</a>, and sulfur.<a class="footnote-ref" id="fnref:65" href="#fn:65">65</a>

Indian alchemists, practitioners of the "science of chemicals" (<a href="/facts/Sanskrit_language/ychfjhlx">Sanskrit</a>: रसशास्त्र, <a href="/facts/Romanization_of_Sanskrit/N1NFy5A4">romanized</a>: rasaśāstra), wrote extensively about the use of sulfur in alchemical operations with mercury, from the eighth century AD onwards.<a class="footnote-ref" id="fnref:66" href="#fn:66">66</a> In the <a href="/facts/Rasa_shastra/vx5lQ4ID">rasaśāstra</a> tradition, sulfur is called "the smelly" (गन्धक, gandhaka).
Early <a href="/facts/Europe/DTAtrKfh">European</a> <a href="/facts/Alchemy/CEx0U1Em">alchemists</a> gave sulfur a unique <a href="/facts/Alchemical_symbol/TIHkrNya">alchemical symbol</a>, a triangle atop a cross (🜍). (This is sometimes confused with the astronomical crossed-spear symbol ⚴ for <a href="/facts/2_Pallas/onjUgYtA">2 Pallas</a>.) The variation known as brimstone has a symbol combining a <a href="/facts/Two-barred_cross/0EfDyHdf">two-barred cross</a> atop a <a href="/facts/Infinity_symbol/xwR5xyT2">lemniscate</a> (🜏). In traditional skin treatment, elemental sulfur was used (mainly in creams) to alleviate such conditions as <a href="/facts/Scabies/QCPVVhQ0">scabies</a>, <a href="/facts/Ringworm/hFyb8T6n">ringworm</a>, <a href="/facts/Psoriasis/WW1k1LsH">psoriasis</a>, <a href="/facts/Eczema/JwlyQBa2">eczema</a>, and <a href="/facts/Acne/TKJxhHSd">acne</a>. The mechanism of action is unknown—though elemental sulfur does oxidize slowly to sulfurous acid, which is (through the action of <a href="/facts/Sulfite/xdppUlKA">sulfite</a>) a mild reducing and antibacterial agent.<a class="footnote-ref" id="fnref:67" href="#fn:67">67</a><a class="footnote-ref" id="fnref:68" href="#fn:68">68</a><a class="footnote-ref" id="fnref:69" href="#fn:69">69</a>

<h3>Modern times</h3>

Sulfur appears in a column of fixed (non-acidic) <a href="/facts/Alkali/s6NqPGSP">alkali</a> in a chemical table of 1718.<a class="footnote-ref" id="fnref:70" href="#fn:70">70</a> <a href="/facts/Antoine_Lavoisier/UheVQrhu">Antoine Lavoisier</a> used sulfur in combustion experiments, writing of some of these in 1777.<a class="footnote-ref" id="fnref:71" href="#fn:71">71</a>
Sulfur deposits in <a href="/facts/Sicily/E6fug03z">Sicily</a> were the dominant source for more than a century. By the late 18th century, about 2,000 tonnes per year of sulfur were imported into <a href="/facts/Marseille/kj7te1HG">Marseille</a>, France, for the production of <a href="/facts/Sulfuric_acid/Wom6fymJ">sulfuric acid</a> for use in the <a href="/facts/Leblanc_process/KkEXaIeE">Leblanc process</a>. In <a href="/facts/Industrial_Revolution/B6E3Fasm">industrializing</a> Britain, with the repeal of <a href="/facts/Tariff/NCluKCm2">tariffs</a> on salt in 1824, demand for sulfur from Sicily surged. The increasing British control and exploitation of the mining, refining, and transportation of sulfur, coupled with the failure of this lucrative export to transform Sicily's backward and impoverished economy, led to the <a href="/facts/Sulfur_Crisis_of_1840/vXHoR9Cc">Sulfur Crisis of 1840</a>, when <a href="/facts/Ferdinand_II_of_the_Two_Sicilies/rdtzILRa">King Ferdinand II</a> gave a monopoly of the sulfur industry to a French firm, violating an earlier 1816 trade agreement with Britain. A peaceful solution was eventually negotiated by France.<a class="footnote-ref" id="fnref:72" href="#fn:72">72</a><a class="footnote-ref" id="fnref:73" href="#fn:73">73</a>
In 1867, elemental sulfur was discovered in underground deposits in <a href="/facts/Louisiana/2GvfFcKE">Louisiana</a> and <a href="/facts/Texas/B987WHF0">Texas</a>. The highly successful <a href="/facts/Frasch_process/47C7d6CU">Frasch process</a> was developed to extract this resource.<a class="footnote-ref" id="fnref:74" href="#fn:74">74</a>
In the late 18th century, <a href="/facts/Furniture/J7JrsrlA">furniture</a> makers used molten sulfur to produce <a href="/facts/Sulfur_inlay/JnEHWFnH">decorative inlays</a>.<a class="footnote-ref" id="fnref:75" href="#fn:75">75</a> Molten sulfur is sometimes still used for setting steel bolts into drilled concrete holes where high shock resistance is desired for floor-mounted equipment attachment points. Pure powdered sulfur was used as a medicinal tonic and laxative.<a class="footnote-ref" id="fnref:76" href="#fn:76">76</a>
Since the advent of the <a href="/facts/Contact_process/vNmmUQ3s">contact process</a>, the majority of sulfur is used to make sulfuric acid for a wide range of uses, particularly fertilizer.<a class="footnote-ref" id="fnref:77" href="#fn:77">77</a>
In recent times, the main source of sulfur has become <a href="/facts/Petroleum/IQV0bHVd">petroleum</a> and <a href="/facts/Natural_gas/9MYQ7NAP">natural gas</a>. This is due to the requirement to remove sulfur from fuels in order to prevent <a href="/facts/Acid_rain/f769GyNz">acid rain</a>, and has resulted in a surplus of sulfur.<a class="footnote-ref" id="fnref:78" href="#fn:78">78</a>

<h3>Spelling and etymology</h3>
Sulfur is derived from the Latin word sulpur, which was <a href="/facts/Hellenized/w07GMufL">Hellenized</a> to sulphur in the erroneous belief that the Latin word came from Greek. This spelling was later reinterpreted as representing an /f/ sound and resulted in the spelling sulfur, which appears in Latin toward the end of the <a href="/facts/Classical_antiquity/JBq8vEX9">Classical period</a>. The true Ancient Greek word for sulfur, θεῖον, theîon (from earlier θέειον, théeion), is the source of the international chemical prefix <a href="/facts/Thio-/kbBJGUaJ">thio-</a>. The Modern Standard Greek word for sulfur is θείο, theío.
In 12th-century <a href="/facts/Anglo-Norman_language/GmwkRAzQ">Anglo-French</a>, it was sulfre. In the 14th century, the erroneously Hellenized Latin -ph- was restored in Middle English sulphre. By the 15th century, both full Latin spelling variants sulfur and sulphur became common in English. The parallel f~ph spellings continued in Britain until the 19th century, when the word was standardized as sulphur.<a class="footnote-ref" id="fnref:79" href="#fn:79">79</a> On the other hand, sulfur was the form eventually chosen in the United States, though multiple place names (such as <a href="/facts/White_Sulphur_Springs_(disambiguation)/8VBuggdY">White Sulphur Springs</a>) use -ph-. Canada uses both spellings.
<a href="/facts/International_Union_of_Pure_and_Applied_Chemistry/2AV6myCK">IUPAC</a> adopted the spelling sulfur in 1990<a class="footnote-ref" id="fnref:80" href="#fn:80">80</a><a class="footnote-ref" id="fnref:81" href="#fn:81">81</a> as did the Nomenclature Committee of the <a href="/facts/Royal_Society_of_Chemistry/1fg4xnqR">Royal Society of Chemistry</a> in 1992, restoring the spelling sulfur to Britain.<a class="footnote-ref" id="fnref:82" href="#fn:82">82</a> <a href="/facts/Oxford_English_Dictionary/qaxKX8Bc">Oxford Dictionaries</a> note that "in chemistry and other technical uses ... the -f- spelling is now the standard form for this and related words in British as well as US contexts, and is increasingly used in general contexts as well."<a class="footnote-ref" id="fnref:83" href="#fn:83">83</a>

<h2 id="production">Production</h2>

Sulfur may be found by itself and historically was usually obtained in this form; <a href="/facts/Pyrite/41CYREyr">pyrite</a> has also been a source of sulfur.<a class="footnote-ref" id="fnref:84" href="#fn:84">84</a> In volcanic regions in <a href="/facts/Sicily/E6fug03z">Sicily</a>, in ancient times, it was found on the surface of the Earth, and the "<a href="/facts/Sicilian_method/aXTozSW9">Sicilian process</a>" was used: sulfur deposits were piled and stacked in brick kilns built on sloping hillsides, with airspaces between them. Then, some sulfur was pulverized, spread over the stacked ore and ignited, causing the free sulfur to melt down the hills. Eventually the surface-borne deposits played out, and miners excavated veins that ultimately dotted the Sicilian landscape with labyrinthine mines. Mining was unmechanized and labor-intensive, with pickmen freeing the ore from the rock, and mine-boys or <a href="/facts/Carusu/7SA4UIjH">carusi</a> carrying baskets of ore to the surface, often through a mile or more of tunnels. Once the ore was at the surface, it was reduced and extracted in smelting ovens. The conditions in <a href="/facts/Sulfur_mining_in_Sicily/27g5U1SJ">Sicilian sulfur mines</a> were horrific, prompting <a href="/facts/Booker_T._Washington/v1z5gmX9">Booker T. Washington</a> to write "I am not prepared just now to say to what extent I believe in a physical hell in the next world, but a sulfur mine in Sicily is about the nearest thing to hell that I expect to see in this life."<a class="footnote-ref" id="fnref:85" href="#fn:85">85</a> Sulfur is still mined from surface deposits in poorer nations with volcanoes, such as <a href="/facts/Indonesia/vQnWU3IW">Indonesia</a>, and problems with working conditions still exist.<a class="footnote-ref" id="fnref:86" href="#fn:86">86</a>
Elemental sulfur was extracted from <a href="/facts/Salt_dome/RsPm1A8y">salt domes</a> (where it sometimes occurs in nearly pure form) until the late 20th century, when it became a side product of other industrial processes such as in oil refining, in which sulfur is undesirable. As a mineral, native sulfur under salt domes is thought to be a fossil mineral resource, produced by the action of anaerobic bacteria on sulfate deposits. It was removed from such salt-dome mines mainly by the <a href="/facts/Frasch_process/47C7d6CU">Frasch process</a>.<a class="footnote-ref" id="fnref:87" href="#fn:87">87</a> In this method, superheated water was pumped into a native sulfur deposit to melt the sulfur, and then compressed air returned the 99.5% pure melted product to the surface. Throughout the 20th century this procedure produced elemental sulfur that required no further purification. Due to a limited number of such sulfur deposits and the high cost of working them, this process for mining sulfur has not had significant use anywhere in the world since 2002.<a class="footnote-ref" id="fnref:88" href="#fn:88">88</a><a class="footnote-ref" id="fnref:89" href="#fn:89">89</a>

Since then, sulfur has typically been produced from petroleum, <a href="/facts/Natural_gas/9MYQ7NAP">natural gas</a>, and related fossil resources, from which it is obtained mainly as <a href="/facts/Hydrogen_sulfide/UbCqjMMk">hydrogen sulfide</a>.<a class="footnote-ref" id="fnref:90" href="#fn:90">90</a> <a href="/facts/Organosulfur_compound/sUxSSXwD">Organosulfur compounds</a>, undesirable impurities in petroleum, may be upgraded by subjecting them to <a href="/facts/Hydrodesulfurization/CTXmxBQu">hydrodesulfurization</a>, which cleaves the C–S bonds:<a class="footnote-ref" id="fnref:91" href="#fn:91">91</a><a class="footnote-ref" id="fnref:92" href="#fn:92">92</a>

R-S-R + 2 H2 → 2 RH + H2S
The resulting hydrogen sulfide from this process, and also as it occurs in natural gas, is converted into elemental sulfur by the <a href="/facts/Claus_process/FbhagLPm">Claus process</a>, which entails oxidation of some hydrogen sulfide to sulfur dioxide and then the <a href="/facts/Comproportionation/XomX78yC">comproportionation</a> of the two:<a class="footnote-ref" id="fnref:93" href="#fn:93">93</a><a class="footnote-ref" id="fnref:94" href="#fn:94">94</a>

3 O2 + 2 H2S → 2 SO2 + 2 H2O
SO2 + 2 H2S → 3 S + 2 H2O

Due to the high sulfur content of the <a href="/facts/Athabasca_Oil_Sands/oGj4xxtn">Athabasca Oil Sands</a>, stockpiles of elemental sulfur from this process exist throughout <a href="/facts/Alberta/PjKJFbJY">Alberta</a>, Canada.<a class="footnote-ref" id="fnref:95" href="#fn:95">95</a> Another way of storing sulfur is as a <a href="/facts/Binder_(material)/GBxjQF0U">binder</a> for concrete, the resulting product having some desirable properties (see <a href="/facts/Sulfur_concrete/9SfXxYII">sulfur concrete</a>).<a class="footnote-ref" id="fnref:96" href="#fn:96">96</a>
The world production of sulfur in 2011 amounted to 69 million tonnes (Mt), with more than 15 countries contributing more than 1 Mt each. Countries producing more than 5 Mt are <a href="/facts/China/lTjIXY5p">China</a> (9.6), the <a href="/facts/United_States/P0sCdLe5">United States</a> (8.8), <a href="/facts/Canada/D5P9yqs6">Canada</a> (7.1) and <a href="/facts/Russia/jfkCwyxn">Russia</a> (7.1).<a class="footnote-ref" id="fnref:97" href="#fn:97">97</a> Production has been slowly increasing from 1900 to 2010; the price was unstable in the 1980s and around 2010.<a class="footnote-ref" id="fnref:98" href="#fn:98">98</a>

<h2 id="applications">Applications</h2>
<h3>Sulfuric acid</h3>
Elemental sulfur is used mainly as a precursor to other chemicals. Approximately 85% (1989) is converted to <a href="/facts/Sulfuric_acid/Wom6fymJ">sulfuric acid</a> (H2SO4):

1⁄8 S8 + 3⁄2 O2 + H2O → H2SO4

In 2010, the United States produced more sulfuric acid than any other inorganic industrial chemical.<a class="footnote-ref" id="fnref:99" href="#fn:99">99</a> The principal use for the acid is the extraction of phosphate ores for the production of fertilizer manufacturing. Other applications of sulfuric acid include oil refining, wastewater processing, and mineral extraction.<a class="footnote-ref" id="fnref:100" href="#fn:100">100</a>

<h3>Other important sulfur chemistry</h3>
Sulfur reacts directly with methane to give <a href="/facts/Carbon_disulfide/b04Tadmy">carbon disulfide</a>, which is used to manufacture <a href="/facts/Cellophane/bpBIL8PX">cellophane</a> and <a href="/facts/Rayon/Us58BuEM">rayon</a>.<a class="footnote-ref" id="fnref:101" href="#fn:101">101</a> One of the uses of elemental sulfur is in <a href="/facts/Vulcanization/jmBUqGaz">vulcanization</a> of rubber, where <a href="/facts/Polysulfide/PpfaUlw4">polysulfide</a> chains crosslink organic polymers. Large quantities of <a href="/facts/Sulfite/xdppUlKA">sulfites</a> are used to <a href="/facts/Bleach_(chemical)/QPxAysPl">bleach</a> <a href="/facts/Paper/FUETwwKV">paper</a> and to preserve <a href="/facts/Dried_fruit/qRBAEoMj">dried fruit</a>. Many <a href="/facts/Surfactant/zgVX6g8o">surfactants</a> and <a href="/facts/Detergent/4FLKXR6p">detergents</a> (e.g. <a href="/facts/Sodium_lauryl_sulfate/H0Q2z7W3">sodium lauryl sulfate</a>) are sulfate derivatives. <a href="/facts/Calcium_sulfate/mTD8oGaH">Calcium sulfate</a>, gypsum (CaSO4·2H2O) is mined on the scale of 100 million <a href="/facts/Tonne/gMymLmWv">tonnes</a> each year for use in <a href="/facts/Portland_cement/kPj8EjnP">Portland cement</a> and fertilizers.
When silver-based <a href="/facts/Photography/ezLPT43M">photography</a> was widespread, sodium and ammonium <a href="/facts/Sodium_thiosulfate/qAMvfeuv">thiosulfate</a> were widely used as "fixing agents". Sulfur is a component of <a href="/facts/Gunpowder/AEcB6HCR">gunpowder</a> ("black powder").

<h3>Fertilizer</h3>
<a href="/facts/Amino_acid/WDxYwBny">Amino acids</a> synthesized by <a href="/facts/Organism/j8JkL09u">living organisms</a> such as <a href="/facts/Methionine/7neydPKo">methionine</a> and <a href="/facts/Cysteine/kbqvUm6d">cysteine</a> contain <a href="/facts/Organosulfur_compounds/sUxSSXwD">organosulfur</a> groups (<a href="/facts/Thioester/UwfKqs1F">thioester</a> and <a href="/facts/Thiol/VemKEDP9">thiol</a> respectively). The <a href="/facts/Antioxidant/4TG4MQ83">antioxidant</a> <a href="/facts/Glutathione/5bSxjusL">glutathione</a> protecting many living organisms against <a href="/facts/Free_radical/g8XthvBS">free radicals</a> and <a href="/facts/Oxidative_stress/HX7dfUUb">oxidative stress</a> also contains organic sulfur. Some <a href="/facts/Crop/JoQKR5R8">crops</a> such as <a href="/facts/Onion/2ajXf00d">onion</a> and <a href="/facts/Garlic/NschLR1S">garlic</a> also produce different <a href="/facts/Organosulfur_compounds/sUxSSXwD">organosulfur compounds</a> such as <a href="/facts/Syn-Propanethial-S-oxide/k39N17wc">syn-propanethial-S-oxide</a> responsible of lacrymal irritation (onions), or <a href="/facts/Diallyl_disulfide/f3JAd8b9">diallyl disulfide</a> and <a href="/facts/Allicin/tPLWtC2a">allicin</a> (garlic). <a href="/facts/Sulfate/yuWVxsUf">Sulfates</a>, commonly found in <a href="/facts/Soil/5Ddpr3QM">soils</a> and <a href="/facts/Groundwater/JYM2IDS2">groundwaters</a> are often a sufficient natural source of sulfur for plants and bacteria. <a href="/facts/Deposition_(aerosol_physics)/HDd7adq7">Atmospheric deposition</a> of <a href="/facts/Sulfur_dioxide/jDK1fIDs">sulfur dioxide</a> (SO2) is also a common artificial source (<a href="/facts/Coal_combustion_products/RJDXs2zI">coal combustion</a>) of sulfur for the soils. Under normal circumstances, in most agricultural soils, sulfur is not a <a href="/facts/Limiting_factor/IYufWHvx">limiting nutrient</a> for plants and <a href="/facts/Microorganism/pysJYcE2">microorganisms</a> (see <a href="/facts/Liebig%2527s_law_of_the_minimum/t27FC947">Liebig's barrel</a>). However, in some circumstances, soils can be depleted in <a href="/facts/Sulfate/yuWVxsUf">sulfate</a>, e.g. if this later is leached by <a href="/facts/Meteoric_water/JSYSHPWq">meteoric water</a> (<a href="/facts/Rain/MLqcQEyx">rain</a>) or if the requirements in sulfur for some types of crops are high. This explains that sulfur is increasingly recognized and used as a component of <a href="/facts/Fertilizer/ysh3r6NJ">fertilizers</a>. The most important form of sulfur for fertilizer is <a href="/facts/Calcium_sulfate/mTD8oGaH">calcium sulfate</a>, commonly found in nature as the mineral <a href="/facts/Gypsum/MItYU70n">gypsum</a> (CaSO4·2H2O). Elemental sulfur is <a href="/facts/Hydrophobic/Ifya0CXQ">hydrophobic</a> (not soluble in water) and cannot be used directly by plants. Elemental sulfur (ES) is sometimes mixed with <a href="/facts/Bentonite/N9Hb8lX9">bentonite</a> to amend depleted soils for crops with high requirement in organo-sulfur. Over time, <a href="/facts/Redox/Pyd5RVcj">oxidation</a> <a href="/facts/Abiotic_component/CA3Dwtta">abiotic</a> processes with <a href="/facts/Earth_atmosphere/FV97Am25">atmospheric</a> <a href="/facts/Oxygen/acyn6o8r">oxygen</a> and <a href="/facts/Soil_microbiology/E9gzHMj2">soil bacteria</a> can <a href="/facts/Redox/Pyd5RVcj">oxidize</a> and convert elemental sulfur to soluble derivatives, which can then be used by microorganisms and plants. Sulfur improves the efficiency of other essential plant nutrients, particularly <a href="/facts/Nitrate/5AnVlYnL">nitrogen</a> and phosphorus.<a class="footnote-ref" id="fnref:102" href="#fn:102">102</a> Biologically produced sulfur particles are naturally <a href="/facts/Hydrophile/k8p95WYu">hydrophilic</a> due to a <a href="/facts/Biopolymer/GaCwr4EY">biopolymer</a> coating and are easier to disperse over the land in a spray of diluted slurry, resulting in a faster uptake by plants.
The plants requirement for sulfur equals or exceeds the requirement for <a href="/facts/Phosphorus/27xCeIqs">phosphorus</a>. It is an <a href="/facts/Plant_nutrition/hXWLy7Sc">essential nutrient for plant</a> growth, <a href="/facts/Root_nodule/qUFHMpsq">root nodule</a> formation of legumes, and immunity and defense systems. Sulfur deficiency has become widespread in many countries in Europe.<a class="footnote-ref" id="fnref:103" href="#fn:103">103</a><a class="footnote-ref" id="fnref:104" href="#fn:104">104</a><a class="footnote-ref" id="fnref:105" href="#fn:105">105</a> Because atmospheric inputs of sulfur continue to decrease, the deficit in the sulfur input/output is likely to increase unless sulfur fertilizers are used. Atmospheric inputs of sulfur decrease because of actions taken to limit <a href="/facts/Acid_rain/f769GyNz">acid rains</a>.<a class="footnote-ref" id="fnref:106" href="#fn:106">106</a><a class="footnote-ref" id="fnref:107" href="#fn:107">107</a>

<h3>Fungicide and pesticide</h3>

Elemental sulfur is one of the oldest fungicides and <a href="/facts/Pesticide/Uhf4KnwJ">pesticides</a>. "Dusting sulfur", elemental sulfur in powdered form, is a common fungicide for grapes, strawberry, many vegetables and several other crops. It has a good efficacy against a wide range of <a href="/facts/Powdery_mildew/qAl00hYE">powdery mildew</a> diseases as well as black spot. In organic production, sulfur is the most important fungicide. It is the only fungicide used in <a href="/facts/Organic_agriculture/Rce4nxdU">organically</a> farmed apple production against the main disease <a href="/facts/Apple_scab/040EfGDW">apple scab</a> under colder conditions. Biosulfur (biologically produced elemental sulfur with hydrophilic characteristics) can also be used for these applications.
Standard-formulation dusting sulfur is applied to crops with a sulfur duster or <a href="/facts/Aerial_application/e0LpTctF">from a dusting plane</a>. Wettable sulfur is the commercial name for dusting sulfur formulated with additional ingredients to make it water <a href="/facts/Miscibility/HwQaolbQ">miscible</a>.<a class="footnote-ref" id="fnref:108" href="#fn:108">108</a><a class="footnote-ref" id="fnref:109" href="#fn:109">109</a> It has similar applications and is used as a <a href="/facts/Fungicide/c1twQBYo">fungicide</a> against <a href="/facts/Mildew/wVos4nxG">mildew</a> and other mold-related problems with plants and soil.
Elemental sulfur powder is used as an "<a href="/facts/Organic_farming/Rce4nxdU">organic</a>" (i.e., "green") <a href="/facts/Insecticide/1xYL3MSD">insecticide</a> (actually an <a href="/facts/Acaricide/y9llKWHg">acaricide</a>) against <a href="/facts/Tick/LNe33WJf">ticks</a> and <a href="/facts/Mite/M52qFjlE">mites</a>. A common method of application is dusting the clothing or limbs with sulfur powder.
A diluted solution of <a href="/facts/Lime_sulfur/hpQrUqCQ">lime sulfur</a> (made by combining <a href="/facts/Calcium_hydroxide/Kz2KzRd8">calcium hydroxide</a> with elemental sulfur in water) is used as a dip for pets to destroy <a href="/facts/Ringworm/hFyb8T6n">ringworm (fungus)</a>, <a href="/facts/Mange/TgeJF3sM">mange</a>, and other <a href="/facts/Cutaneous_conditions/Vkr5XpeG">dermatoses</a> and <a href="/facts/Parasitism/HWPcgky7">parasites</a>.
Sulfur candles of almost pure sulfur were burned to <a href="/facts/Fumigant/QGCodNPb">fumigate</a> structures and wine barrels, but are now considered too toxic for residences.

<h3>Pharmaceuticals</h3>
Main article: <a href="/facts/Sulfur_(pharmacy)/tqbCKwuq">Sulfur (pharmacy)</a>
Sulfur (specifically <a href="/facts/Octasulfur/sub03Upn">octasulfur</a>, S8) is used in pharmaceutical skin preparations for the treatment of <a href="/facts/Acne/TKJxhHSd">acne</a> and other conditions. It acts as a <a href="/facts/Keratolytic/hEtMwHCa">keratolytic</a> agent and also kills bacteria, fungi, <a href="/facts/Scabies/QCPVVhQ0">scabies</a> mites, and other parasites.<a class="footnote-ref" id="fnref:110" href="#fn:110">110</a> Precipitated sulfur and colloidal sulfur are used, in form of <a href="/facts/Lotion/GXollPbk">lotions</a>, creams, powders, soaps, and bath additives, for the treatment of <a href="/facts/Acne_vulgaris/TKJxhHSd">acne vulgaris</a>, <a href="/facts/Acne_rosacea/jxYUX2ml">acne rosacea</a>, and <a href="/facts/Seborrhoeic_dermatitis/d1CfhTDG">seborrhoeic dermatitis</a>.<a class="footnote-ref" id="fnref:111" href="#fn:111">111</a>
Many drugs contain sulfur.<a class="footnote-ref" id="fnref:112" href="#fn:112">112</a> Early examples include antibacterial <a href="/facts/Sulfonamide_(medicine)/4vXtwwwm">sulfonamides</a>, known as sulfa drugs. A more recent example is mucolytic <a href="/facts/Acetylcysteine/78TaGKtg">acetylcysteine</a>. Sulfur is a part of many bacterial defense molecules. Most <a href="/facts/%25CE%2592-lactam/jasUACD2">β-lactam</a> antibiotics, including the <a href="/facts/Penicillin/Abo8VQ3p">penicillins</a>, <a href="/facts/Cephalosporins/WeB7I75T">cephalosporins</a> and <a href="/facts/Monobactam/EYumf0C5">monobactams</a> contain sulfur.<a class="footnote-ref" id="fnref:113" href="#fn:113">113</a>

<h3>Batteries</h3>
Due to their high energy density and the availability of sulfur, there is ongoing research in creating rechargeable <a href="/facts/Lithium%25E2%2580%2593sulfur_battery/RPo9joIf">lithium–sulfur batteries</a>. Until now, carbonate electrolytes have caused failures in such batteries after a single cycle. In February 2022, researchers at <a href="/facts/Drexel_University/t1CjDDmE">Drexel University</a> have not only created a prototypical battery that lasted 4000 recharge cycles, but also found the first monoclinic gamma sulfur that remained stable below 95 degrees Celsius.<a class="footnote-ref" id="fnref:114" href="#fn:114">114</a>

<h2 id="biological-role">Biological role</h2>
Sulfur is an essential component of all living <a href="/facts/Cell_(biology)/bLM9UQvy">cells</a>. It is the eighth most abundant element in the human body by weight,<a class="footnote-ref" id="fnref:115" href="#fn:115">115</a> about equal in abundance to <a href="/facts/Potassium/5lcumVgo">potassium</a>, and slightly greater than <a href="/facts/Sodium/eYuSPu2V">sodium</a> and <a href="/facts/Chlorine/y27UwYBM">chlorine</a>.<a class="footnote-ref" id="fnref:116" href="#fn:116">116</a> A 70 kg (150 lb) human body contains about 140 grams (4.9 oz) of sulfur.<a class="footnote-ref" id="fnref:117" href="#fn:117">117</a> The main dietary source of sulfur for humans is <a href="/facts/Sulfur-containing_amino_acids/WDxYwBny">sulfur-containing amino acids</a>,<a class="footnote-ref" id="fnref:118" href="#fn:118">118</a> which can be found in plant and animal proteins.<a class="footnote-ref" id="fnref:119" href="#fn:119">119</a>

<h3>Transferring sulfur between inorganic and biomolecules</h3>
See also: <a href="/facts/Sulfur_cycle/NzCakgxd">Sulfur cycle</a> and <a href="/facts/Sulfur_metabolism/yxpNrHGW">Sulfur metabolism</a>
In the 1880s, while studying <a href="/facts/Beggiatoa/oRvSqLwr">Beggiatoa</a> (a bacterium living in a sulfur rich environment), <a href="/facts/Sergei_Winogradsky/abdvjtVP">Sergei Winogradsky</a> found that it oxidized <a href="/facts/Hydrogen_sulfide/UbCqjMMk">hydrogen sulfide</a> (H2S) as an energy source, forming intracellular sulfur droplets. Winogradsky referred to this form of metabolism as inorgoxidation (oxidation of inorganic compounds).<a class="footnote-ref" id="fnref:120" href="#fn:120">120</a> Another contributor, who continued to study it was <a href="/facts/Selman_Waksman/sq4CBkQ5">Selman Waksman</a>.<a class="footnote-ref" id="fnref:121" href="#fn:121">121</a> Primitive bacteria that live around deep ocean <a href="/facts/Hydrothermal_vent/0xPqNUkY">volcanic vents</a> oxidize hydrogen sulfide for their nutrition, as discovered by <a href="/facts/Robert_Ballard/EbKTTXTp">Robert Ballard</a>.<a class="footnote-ref" id="fnref:122" href="#fn:122">122</a>
Sulfur oxidizers can use as energy sources reduced sulfur compounds, including hydrogen sulfide, elemental sulfur, <a href="/facts/Sulfite/xdppUlKA">sulfite</a>, <a href="/facts/Thiosulfate/LYu0KhDu">thiosulfate</a>, and various <a href="/facts/Polythionates/DTpMojXJ">polythionates</a> (e.g., <a href="/facts/Tetrathionate/D5uVIFdJ">tetrathionate</a>).<a class="footnote-ref" id="fnref:123" href="#fn:123">123</a> They depend on enzymes such as <a href="/facts/Sulfur_dioxygenase/tXs215KS">sulfur oxygenase</a> and <a href="/facts/Sulfite_oxidase/WnrJJ489">sulfite oxidase</a> to oxidize sulfur to sulfate. Some <a href="/facts/Lithotroph/1CboHMzX">lithotrophs</a> can even use the energy contained in sulfur compounds to produce sugars, a process known as <a href="/facts/Chemosynthesis/AFUdIqc5">chemosynthesis</a>. Some <a href="/facts/Bacteria/wC8xSCsU">bacteria</a> and <a href="/facts/Archaea/Adxh0aHw">archaea</a> use hydrogen sulfide in place of water as the <a href="/facts/Electron_donor/7JxwwW43">electron donor</a> in chemosynthesis, a process similar to <a href="/facts/Photosynthesis/TMV7w693">photosynthesis</a> that produces sugars and uses oxygen as the <a href="/facts/Electron_acceptor/sRvhMXqH">electron acceptor</a>. Sulfur-based chemosynthesis may be simplifiedly compared with photosynthesis:

H2S + CO2 → sugars + S
H2O + CO2 → sugars + O2
There are bacteria combining these two ways of nutrition: <a href="/facts/Green_sulfur_bacteria/rb7cNcX8">green sulfur bacteria</a> and <a href="/facts/Purple_sulfur_bacteria/h3f5dFUn">purple sulfur bacteria</a>.<a class="footnote-ref" id="fnref:124" href="#fn:124">124</a> Also sulfur-oxidizing bacteria can go into symbiosis with larger organisms, enabling the later to use hydrogen sulfide as food to be oxidized. Example: the <a href="/facts/Giant_tube_worm/Vgu0GSwC">giant tube worm</a>.<a class="footnote-ref" id="fnref:125" href="#fn:125">125</a>
There are <a href="/facts/Sulfate-reducing_bacteria/uvFQhLWe">sulfate-reducing bacteria</a>, that, by contrast, "breathe sulfate" instead of oxygen. They use organic compounds or molecular hydrogen as the energy source. They use sulfur as the electron acceptor, and reduce various oxidized sulfur compounds back into sulfide, often into hydrogen sulfide. They can grow on other partially oxidized sulfur compounds (e.g. thiosulfates, thionates, polysulfides, sulfites).
There are studies pointing that many deposits of native sulfur in places that were the bottom of <a href="/facts/Tethys_Ocean/X2b2FIu3">the ancient oceans</a> have biological origin.<a class="footnote-ref" id="fnref:126" href="#fn:126">126</a><a class="footnote-ref" id="fnref:127" href="#fn:127">127</a><a class="footnote-ref" id="fnref:128" href="#fn:128">128</a> These studies indicate that this native sulfur have been obtained through biological activity, but what is responsible for that (sulfur-oxidizing bacteria or sulfate-reducing bacteria) is still unknown for sure.
Sulfur is absorbed by <a href="/facts/Plant/X5BMDMvS">plants</a> <a href="/facts/Root/Hk7ucczM">roots</a> from soil as <a href="/facts/Sulfate/yuWVxsUf">sulfate</a> and transported as a phosphate ester. Sulfate is reduced to sulfide via sulfite before it is incorporated into <a href="/facts/Cysteine/kbqvUm6d">cysteine</a> and other organosulfur compounds.<a class="footnote-ref" id="fnref:129" href="#fn:129">129</a>

SO2−4 → SO2−3 → H2S → cysteine (thiol) → methionine (thioether)
While the plants' role in transferring sulfur to animals by <a href="/facts/Food_chain/mvDKQTGu">food chains</a> is more or less understood, the role of sulfur bacteria is just getting investigated.<a class="footnote-ref" id="fnref:130" href="#fn:130">130</a><a class="footnote-ref" id="fnref:131" href="#fn:131">131</a>

<h3>Protein and organic metabolites</h3>
In all forms of life, most of the sulfur is contained in two <a href="/facts/Proteinogenic_amino_acid/xoXITvm0">proteinogenic amino acids</a> (<a href="/facts/Cysteine/kbqvUm6d">cysteine</a> and <a href="/facts/Methionine/7neydPKo">methionine</a>), thus the element is present in all <a href="/facts/Protein/Jxmagu3E">proteins</a> that contain these amino acids.<a class="footnote-ref" id="fnref:132" href="#fn:132">132</a> Some of the sulfur is present in certain metabolites—many of which are <a href="/facts/Cofactor_(biochemistry)/AGo0PCUU">cofactors</a>—and sulfated polysaccharides of <a href="/facts/Connective_tissue/mal3fc7k">connective tissue</a> (<a href="/facts/Chondroitin_sulfate/Mf16uA7g">chondroitin sulfates</a>, <a href="/facts/Heparin/4lxSm2pB">heparin</a>).

The functionality of a given protein is heavily dependent on its structure. Proteins reach this structure through the process of <a href="/facts/Protein_folding/rf3nR2Y1">protein folding</a>, which is facilitated by a variety of intra- and inter-molecular bonds. While much of the folding is driven by the formation of <a href="/facts/Hydrogen_bond/85V86IIg">hydrogen bonds</a>, <a href="/facts/Covalent_bond/EzMLf3Pz">covalent bonding</a> of cysteine residues into disulfide bridges imposes constraints that stabilize particular conformations while preventing others from forming. As the <a href="/facts/Bond_energy/q4be3EeR">bond energy</a> of a covalent disulfide bridge is higher than the energy of a <a href="/facts/Coordinate_covalent_bond/t7NPflnQ">coordinate bond</a> or hydrophobic interaction, greater numbers of disulfide bridges lead to higher energies required for protein <a href="/facts/Denaturation_(biochemistry)/Eh1hc3Bg">denaturation</a>. Disulfide bonds often serve to stabilize protein structures in the more oxidizing conditions of the extracellular environment.<a class="footnote-ref" id="fnref:133" href="#fn:133">133</a> Within the <a href="/facts/Cytoplasm/Wa0sE6xf">cytoplasm</a>, disulfide bonds may instead be reduced (i.e. in -SH form) to their constituent cysteine residues by <a href="/facts/Thioredoxin/Up6p35ke">thioredoxins</a>.<a class="footnote-ref" id="fnref:134" href="#fn:134">134</a>
Many important cellular enzymes use prosthetic groups ending with sulfhydryl (-SH) moieties to handle reactions involving acyl-containing biochemicals: two common examples from basic metabolism are <a href="/facts/Coenzyme_A/loAfeGpx">coenzyme A</a> and <a href="/facts/Alpha-lipoic_acid/9wTHHWBf">alpha-lipoic acid</a>.<a class="footnote-ref" id="fnref:135" href="#fn:135">135</a> Cysteine-related metabolites <a href="/facts/Homocysteine/m4cgrRBG">homocysteine</a> and <a href="/facts/Taurine/Gol6r2l3">taurine</a> are other sulfur-containing amino acids that are similar in structure, but not coded by <a href="/facts/DNA/nB89Iauz">DNA</a>, and are not part of the <a href="/facts/Primary_structure/VaN6MEYh">primary structure</a> of proteins, take part in various locations of mammalian physiology.<a class="footnote-ref" id="fnref:136" href="#fn:136">136</a><a class="footnote-ref" id="fnref:137" href="#fn:137">137</a> Two of the 13 classical vitamins, <a href="/facts/Biotin/WAaVxyB7">biotin</a> and <a href="/facts/Thiamine/37RC4MCS">thiamine</a>, contain sulfur, and serve as cofactors to several enzymes.<a class="footnote-ref" id="fnref:138" href="#fn:138">138</a><a class="footnote-ref" id="fnref:139" href="#fn:139">139</a>
In intracellular chemistry, sulfur operates as a carrier of reducing hydrogen and its electrons for cellular repair of oxidation. Reduced <a href="/facts/Glutathione/5bSxjusL">glutathione</a>, a sulfur-containing tripeptide, is a reducing agent through its sulfhydryl (–SH) moiety derived from <a href="/facts/Cysteine/kbqvUm6d">cysteine</a>.
<a href="/facts/Methanogenesis/5sA0no5A">Methanogenesis</a>, the route to most of the world's methane, is a multistep biochemical transformation of <a href="/facts/Carbon_dioxide/xGzpppEp">carbon dioxide</a>. This conversion requires several organosulfur cofactors. These include <a href="/facts/Coenzyme_M/Eo0vGNS1">coenzyme M</a>, CH3SCH2CH2SO−3, the immediate precursor to <a href="/facts/Methane/kBHneYnh">methane</a>.<a class="footnote-ref" id="fnref:140" href="#fn:140">140</a>

<h3>Metalloproteins and inorganic cofactors</h3>
Metalloproteins—in which the active site is a transition metal ion (or metal-sulfide cluster) often coordinated by sulfur atoms of cysteine residues<a class="footnote-ref" id="fnref:141" href="#fn:141">141</a>—are essential components of enzymes involved in electron transfer processes. Examples include <a href="/facts/Plastocyanin/kL1atXsa">plastocyanin</a> (Cu2+) and <a href="/facts/Nitrous-oxide_reductase/N1KDg6eg">nitrous oxide reductase</a> (Cu–S). The function of these enzymes is dependent on the fact that the transition metal ion can undergo <a href="/facts/Redox_reaction/Pyd5RVcj">redox reactions</a>. Other examples include many zinc proteins,<a class="footnote-ref" id="fnref:142" href="#fn:142">142</a> as well as <a href="/facts/Iron%25E2%2580%2593sulfur_cluster/QCbnrAF0">iron–sulfur clusters</a>. Most pervasive are the <a href="/facts/Ferrodoxin/1qJJjQHk">ferrodoxins</a>, which serve as electron shuttles in cells. In bacteria, the important <a href="/facts/Nitrogenase/gIhxgCaL">nitrogenase</a> enzymes contain an Fe–Mo–S cluster and is a <a href="/facts/Catalyst/LPBS7TQC">catalyst</a> that performs the important function of <a href="/facts/Nitrogen_fixation/TeLoBpWS">nitrogen fixation</a>, converting atmospheric nitrogen to ammonia that can be used by microorganisms and plants to make proteins, DNA, RNA, alkaloids, and the other organic nitrogen compounds necessary for life.<a class="footnote-ref" id="fnref:143" href="#fn:143">143</a>
Sulfur is also present in <a href="/facts/Molybdenum_cofactor/7XSGmN4J">molybdenum cofactor</a>.<a class="footnote-ref" id="fnref:144" href="#fn:144">144</a>

<h3>Sulfate</h3>
Main article: <a href="/facts/Sulfation/lI6B3Y1M">Sulfation § Sulfation in biology</a>
<h3>Deficiency</h3>
In humans <a href="/facts/Methionine/7neydPKo">methionine</a> is an <a href="/facts/Essential_amino_acid/Re9Rxb9I">essential amino acid</a>; <a href="/facts/Cysteine/kbqvUm6d">cysteine</a> is conditionally essential and may be synthesized from non-essential <a href="/facts/Serine/CM6QWruE">serine</a> via sulfur salvaged from methionine. Sulfur deficiency is uncommon due to the ubiquity of cysteine and methionine in food. 
Isolated sulfite oxidase deficiency is a rare, fatal genetic disease caused by mutations to <a href="/facts/Sulfite_oxidase/WnrJJ489">sulfite oxidase</a>, which is needed to metabolize sulfites to sulfates.<a class="footnote-ref" id="fnref:145" href="#fn:145">145</a>

<h2 id="precautions">Precautions</h2>

Though elemental sulfur is only minimally absorbed through the skin and is of low toxicity to humans, inhalation of sulfur dust or contact with eyes or skin may cause irritation. Excessive ingestion of sulfur can cause a burning sensation or diarrhea,<a class="footnote-ref" id="fnref:146" href="#fn:146">146</a> and cases of life-threatening metabolic acidosis have been reported after patients deliberately consumed sulfur as a folk remedy.<a class="footnote-ref" id="fnref:147" href="#fn:147">147</a><a class="footnote-ref" id="fnref:148" href="#fn:148">148</a>

<h3>Toxicity of sulfur compounds</h3>
When sulfur burns in air, it produces <a href="/facts/Sulfur_dioxide/jDK1fIDs">sulfur dioxide</a>. In water, this gas produces sulfurous acid and sulfites; sulfites are antioxidants that inhibit growth of aerobic bacteria and a useful <a href="/facts/Food_additive/jGk8zjn8">food additive</a> in small amounts. At high concentrations these acids harm the <a href="/facts/Human_lungs/gTWXI6Fj">lungs</a>, <a href="/facts/Human_eyes/a24ua4fy">eyes</a>, or other <a href="/facts/Biological_tissue/H7CpML7A">tissues</a>.<a class="footnote-ref" id="fnref:149" href="#fn:149">149</a> In organisms without lungs such as insects, sulfite in high concentration prevents <a href="/facts/Respiration_(physiology)/KKWAJIbd">respiration</a>.<a class="footnote-ref" id="fnref:150" href="#fn:150">150</a>
<a href="/facts/Sulfur_trioxide/Ijvm08Lq">Sulfur trioxide</a> (made by catalysis from sulfur dioxide) and <a href="/facts/Sulfuric_acid/Wom6fymJ">sulfuric acid</a> are similarly highly acidic and corrosive in the presence of water. Concentrated sulfuric acid is a strong dehydrating agent that can strip available water molecules and water components from sugar and organic tissue.<a class="footnote-ref" id="fnref:151" href="#fn:151">151</a>
The burning of <a href="/facts/Coal/83kV3qxg">coal</a> and/or <a href="/facts/Petroleum/IQV0bHVd">petroleum</a> by industry and <a href="/facts/Power_plants/vYeVY1fD">power plants</a> generates sulfur dioxide (SO2) that reacts with atmospheric water and oxygen to produce <a href="/facts/Sulfurous_acid/2qtYNHAB">sulfurous acid</a> (H2SO3).<a class="footnote-ref" id="fnref:152" href="#fn:152">152</a> These acids are components of <a href="/facts/Acid_rain/f769GyNz">acid rain</a>, lowering the <a href="/facts/PH/RnSv8D7y">pH</a> of <a href="/facts/Soil/5Ddpr3QM">soil</a> and freshwater bodies, sometimes resulting in substantial damage to the <a href="/facts/Environment_(biophysical)/PNzMrGrz">environment</a> and <a href="/facts/Chemical_weathering/uSYGlv0H">chemical weathering</a> of statues and structures. Fuel standards increasingly require that fuel producers extract sulfur from <a href="/facts/Fossil_fuel/BPgxAqB7">fossil fuels</a> to prevent acid rain formation. This extracted and refined sulfur represents a large portion of sulfur production. In coal-fired power plants, <a href="/facts/Flue_gas/ETBGr9II">flue gases</a> are sometimes purified. More modern power plants that use <a href="/facts/Synthesis_gas/VfslxkIN">synthesis gas</a> extract the sulfur before they burn the gas.
<a href="/facts/Hydrogen_sulfide/UbCqjMMk">Hydrogen sulfide</a> is about one-half as <a href="/facts/Toxic/qa96rs60">toxic</a> as <a href="/facts/Hydrogen_cyanide/vNtA0Mxe">hydrogen cyanide</a>, and intoxicates by the same mechanism (inhibition of the respiratory enzyme <a href="/facts/Cytochrome_oxidase/U67QVCv8">cytochrome oxidase</a>),<a class="footnote-ref" id="fnref:153" href="#fn:153">153</a> though hydrogen sulfide is less likely to cause sudden poisonings from small inhaled amounts (near its <a href="/facts/Permissible_exposure_limit/IrQeETWy">permissible exposure limit</a> (PEL) of 20 ppm) because of its disagreeable odor.<a class="footnote-ref" id="fnref:154" href="#fn:154">154</a> However, its presence in ambient air at concentration over 100–150 ppm quickly deadens the sense of smell,<a class="footnote-ref" id="fnref:155" href="#fn:155">155</a> and a victim may breathe increasing quantities without noticing until severe symptoms cause death. Dissolved <a href="/facts/Sulfide/d8YMjLeu">sulfide</a> and <a href="/facts/Hydrosulfide/xIwK8as1">hydrosulfide</a> salts are toxic by the same mechanism.

<h2 id="notes">Notes</h2>

<h2 id="see-also">See also</h2>
<ul>
<li>Chemistry portal</li></ul>
<ul><li><a href="/facts/Blue_lava/WnVvXlS7">Blue lava</a></li>
<li><a href="/facts/Stratospheric_sulfur_aerosols/vgSvuroe">Stratospheric sulfur aerosols</a></li>
<li><a href="/facts/Sulfur_assimilation/8GCaCYMz">Sulfur assimilation</a></li>
<li><a href="/facts/Sulfur_isotope_biogeochemistry/98zskyIs">Sulfur isotope biogeochemistry</a></li>
<li><a href="/facts/Ultra-low_sulfur_diesel/TedIPWwz">Ultra-low sulfur diesel</a></li></ul>

<h2 id="further-reading">Further reading</h2>

Wikiquote has quotations related to Sulfur.

Sigel, Astrid; Freisinger, Eva; Sigel, Roland K.O., eds. (2020). Transition Metals and Sulfur: A Strong Relationship for Life. Guest Editors Martha E Sosa Torres and Peter M.H.Kroneck. Berlin/Boston: de Gruyter. pp. xlv+455. <a href="/facts/ISBN_(identifier)/15AdSPa9">ISBN</a> 978-3-11-058889-7.

<h2 id="external-links">External links</h2>
<ul><li><a href="http://www.periodicvideos.com/videos/016.htm">Sulfur</a> at <a href="/facts/The_Periodic_Table_of_Videos/vC5kbN0M">The Periodic Table of Videos</a> (University of Nottingham)</li>
<li><a href="https://physics.nist.gov/PhysRefData/Handbook/Tables/sulfurtable1.htm">Atomic Data for Sulfur</a>, <a href="/facts/NIST/gr9Fnh85">NIST</a> Physical Measurement Laboratory</li>
<li><a href="https://library.tedankara.k12.tr/chemistry/vol2/allotropy/z129.htm">Sulfur phase diagram</a> <a href="https://web.archive.org/web/20100223201329/http://library.tedankara.k12.tr/chemistry/vol2/allotropy/z129.htm">Archived</a> 23 February 2010 at the <a href="/facts/Wayback_Machine/nmQ3a6JC">Wayback Machine</a>, Introduction to Chemistry for Ages 13–17</li>
<li><a href="https://www.swisseduc.ch/stromboli/perm/vulcano/sulphur-vulcano-en.html">Crystalline, liquid and polymerization of sulfur on Vulcano Island, Italy</a></li>
<li><a href="http://extoxnet.orst.edu/pips/sulfur.htm">Sulfur and its use as a pesticide</a></li>
<li><a href="https://www.sulphurinstitute.org/">The Sulphur Institute</a></li>
<li><a href="https://web.archive.org/web/20140714221502/http://www.nutrientstewardship.com/partners/products-and-services/sulfur-institute">Nutrient Stewardship and The Sulphur Institute</a></li></ul>

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

<ol>
<li id="fn:1">Nature Chemistry 1, 333 (2009). doi:10.1038/nchem.301 <a href="http://www.nature.com/nchem/journal/v1/n5/full/nchem.301.html" target="_blank">http://www.nature.com/nchem/journal/v1/n5/full/nchem.301.html</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></li>
<li id="fn:2">Greenwood, N. N.; Earnshaw, A. (1997). Chemistry of the Elements (2nd ed.). Oxford: Butterworth-Heinemann. ISBN 0-7506-3365-4. <a href="0-7506-3365-4" target="_blank">0-7506-3365-4</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></li>
<li id="fn:3">Chisholm, Hugh, ed. (1911). "Brimstone" . Encyclopædia Britannica. Vol. 4 (11th ed.). Cambridge University Press. p. 571. <a href="/wiki/Hugh_Chisholm" target="_blank">/wiki/Hugh_Chisholm</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></li>
<li id="fn:4">Laurence Knight (19 July 2014). "Sulphur surplus: Up to our necks in a diabolical element". BBC. <a href="https://www.bbc.com/news/magazine-28369829" target="_blank">https://www.bbc.com/news/magazine-28369829</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></li>
<li id="fn:5">"Sulfur". Elements. BBC. 11 October 2014.. Download here. <a href="https://www.bbc.co.uk/programmes/p027xnp2" target="_blank">https://www.bbc.co.uk/programmes/p027xnp2</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></li>
<li id="fn:6">Rettig, S. J.; Trotter, J. (15 December 1987). "Refinement of the structure of orthorhombic sulfur, α-S8" (PDF). Acta Crystallographica Section C. 43 (12): 2260–2262. Bibcode:1987AcCrC..43.2260R. doi:10.1107/S0108270187088152. ISSN 0108-2701. <a href="http://journals.iucr.org/c/issues/1987/12/00/a27614/a27614.pdf" target="_blank">http://journals.iucr.org/c/issues/1987/12/00/a27614/a27614.pdf</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></li>
<li id="fn:7">But impure samples have an odor similar to that of matches. A strong odor called "smell of sulfur" actually is given off by several sulfur compounds, such as hydrogen sulfide and organosulfur compounds. <a href="/wiki/Match" target="_blank">/wiki/Match</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></li>
<li id="fn:8">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).[14]
Greenwood and Earnshaw say that at fast heating for microcrystalline α-S8 the melting point is 115.1 °C (239.2 °F).[9] <a href="#fnref:8" class="footnote-back-ref">↩</a></li>
<li id="fn:9">Greenwood, N. N.; Earnshaw, A. (1997). Chemistry of the Elements (2nd ed.). Oxford: Butterworth-Heinemann. ISBN 0-7506-3365-4. <a href="0-7506-3365-4" target="_blank">0-7506-3365-4</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></li>
<li id="fn:10">Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 645–665. ISBN 978-0-08-037941-8. <a href="978-0-08-037941-8" target="_blank">978-0-08-037941-8</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></li>
<li id="fn:11">Poling, Bruce E.; Prausnitz, John M.; O'Connell, John P. (27 November 2000). The Properties of Gases and Liquids 5E. McGraw Hill Professional. ISBN 978-0-07-149999-6. <a href="978-0-07-149999-6" target="_blank">978-0-07-149999-6</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></li>
<li id="fn:12">Historically, it was rather difficult to find the exact melting point of sulfur.[17] When heated slowly, the melting point may range from 114.6 °C (238.3 °F) to 120.4 °C (248.7 °F)[9] (factors that interfere with a definite melting point, are the polymerlike nature of sulfur[18] and a large number of allotropes.[19]) Melting point may be presented as a temperature range, depending on the allotropic composition of a sample at the time of melting. <a href="#fnref:12" class="footnote-back-ref">↩</a></li>
<li id="fn:13">Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 645–665. ISBN 978-0-08-037941-8. <a href="978-0-08-037941-8" target="_blank">978-0-08-037941-8</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></li>
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</ol>

Sulfur open-in-new

Sulfur