Pengguna:Agung.karjono/Bak pasir/Timbal(II) nitrat

en:Sulfur

Belerang

Halaman ini berisi artikel tentang the chemical element. Untuk kegunaan lain, lihat Agung.karjono/Bak pasir/Timbal(II) nitrat (disambiguasi).

16S Belerang
Sampel belerang elemental
Garis spektrum belerang
Sifat umum
Pengucapan	/bêlèrang/
Alotrop	lihat alotrop belerang
Penampilan	mikrokristal tersinter berwarna kuning lemon
Belerang dalam tabel periodik
16S Hidrogen Helium Lithium Berilium Boron Karbon Nitrogen Oksigen Fluor Neon Natrium Magnesium Aluminium Silikon Fosfor Sulfur Clor Argon Potasium Kalsium Skandium Titanium Vanadium Chromium Mangan Besi Cobalt Nikel Tembaga Seng Gallium Germanium Arsen Selen Bromin Kripton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson O ↑ S ↓ Se fosforus ← belerang → klorin Lihat bagan navigasi yang diperbesar
Nomor atom (Z)	16
Golongan	golongan 16 (kalkogen)
Periode	periode 3
Blok	blok-p
Kategori unsur	nonlogam poliatomik
Berat atom standar (Ar)	[32,059, 32,076] 32,06±0,02 (diringkas)
Konfigurasi elektron	[Ne] 3s2 3p4
Elektron per kelopak	2, 8, 6
Sifat fisik
Fase pada STS (0 °C dan 101,325 kPa)	padat
Titik lebur	388,36 K ​(115,21 °C, ​239,38 °F)
Titik didih	717,8 K ​(444,6 °C, ​832,3 °F)
Kepadatan mendekati s.k.	alfa: 2.07 g/cm3 beta: 1.96 g/cm3 gama: 1.92 g/cm3
saat cair, pada t.l.	1,819 g/cm3
Titik kritis	1314 K, 20,7 MPa
Kalor peleburan	mono: 1,727 kJ/mol
Kalor penguapan	mono: 45 kJ/mol
Kapasitas kalor molar	22,75 J/(mol·K)
Tekanan uap P (Pa) 1 10 100 1 k 10 k 100 k pada T (K) 375 408 449 508 591 717
Sifat atom
Bilangan oksidasi	−2, −1, 0, +1, +2, +3, +4, +5, +6 (oksida asam kuat)
Elektronegativitas	Skala Pauling: 2,58
Energi ionisasi	ke-1: 999,6 kJ/mol ke-2: 2252 kJ/mol ke-3: 3357 kJ/mol (artikel)
Jari-jari kovalen	105±3 pm
Jari-jari van der Waals	180 pm
Lain-lain
Kelimpahan alami	primordial
Struktur kristal	​ortorombus
Konduktivitas termal	0,205 W/(m·K) (amorf)
Resistivitas listrik	2×1015 Ω·m (suhu 20 °C) (amorf)
Arah magnet	diamagnetik
Suseptibilitas magnetik molar	(α) −15,5×10−6 cm3/mol (298 K)
Modulus curah	7,7 GPa
Skala Mohs	2,0
Nomor CAS	7704-34-9
Sejarah
Penemuan	orang Tionghoa (sebelum 2000 SM)
Diketahui sebagai unsur kimia oleh	A. Lavoisier (1777)
Isotop belerang yang utama
Iso­top Kelim­pahan Waktu paruh (t1/2) Mode peluruhan Pro­duk 32S 94,99% stabil 33S 0,75% stabil 34S 4,25% stabil 35S renik 87,37 hri β− 35Cl 36S 0,01% stabil

Belerang adalah unsur kimia dengan lambang S dan nomor atom 16. Unsur ini melimpah, multivalen dan nonlogam. Pada kondisi normal, atom-atom belerang membentuk molekul oktatomik siklik dengan dengan rumus kimia S₈. Unsur belerang berwarna kuning terang, berbentuk kristal padat pada suhu ruang.

Belerang adalah unsur paling umum ke-10 (berdasarkan massa) di alam semesta, dan paling umum ke-5 di Bumi. Meskipun kadang-kadang ditemukan dalam bentuk murni dan alami, belerang di Bumi biasanya terdapat sebagai sulfida dan mineral sulfat. Sebagai unsur yang melimpah dalam bentuk alaminya, belerang dikenal sejak zaman kuno, disebutkan penggunaannya di era India kuno, Yunani kuno, Tiongkok kuno, dan Mesir kuno. Dahulu dan dalam literatur, belerang juga disebut sebagai brimstone, yang berarti "batu bakar". Sekarang, hampir seluruh belerang elemental diproduksi sebagai produk samping dari penyingkiran kontaminan belerang dari gas alam dan minyak bumi. Penggunaan komersial terbesar unsur ini adalah produksi asam sulfat untuk pupuk sulfat dan fosfat, serta proses kimiawi lainnya. Unsur belerang digunakan dalam korek api, insektisida, dan fungisida. Banyak senyawa belerang berbau busuk, dan bau gas alam, bau sigung, jeruk bali, dan bawang putih disebabkan oleh senyawa organosulfur. Hidrogen sulfida memberikan bau khas pada telur busuk dan proses biologis lainnya.

Belerang adalah unsur penting untuk semua kehidupan, tetapi hampir selalu dalam bentuk senyawa organosulfur atau sulfida logam. Tiga asam amino (sistein, sistin, dan metionin) dan dua vitamin (biotin dan tiamin) adalah senyawa organosulfur. Banyak kofaktor juga mengandung belerang, termasuk glutation, thioredoksin, dan Protein besi–belerang. Disulfida, ikatan S–S, memberi kekuatan mekanis dan ketaklarutan protein keratin, yang ditemukan di kulit luar, rambut, dan bulu. Belerang adalah salah satu unsur kimia inti yang dibutuhkan untuk fungsi biokimia dan unsur hara makro bagi semua organisme hidup.

Karakteristik

Ketika terbakar, belerang meleleh menjadi cairan berwarna merah darah dan memancarkan nyala api biru.

Sifat fisik

Belerang membentuk beberapa molekul poliatomik. Alotropi yang terkenal adalah oktasulfur, siklo-S₈. Grup titik siklo-S₈ adalah D_4d dan momen dipolnya adalah 0 D. Oktasulfur adalah padatan lunak yang tak berbau dan berwarna kuning cerah, tetapi sampel tak murninya berbau mirip korek api. Belerang meleleh pada 11.521 °C (20.770 °F), mendidih pada 4.446 °C (8.035 °F) dan mudah mengalami penyubliman. Pada 952 °C (1.746 °F), di bawah titik leburnya, siklo-oktasulfur berubah dari α-oktasulfur menjadi β-polymorph. Struktur cincin S₈ secara virtual tidak berubah, yang mempengaruhi interksi intermolekulernya. Di antara titik lebur dan didihnya, oktasulfur mengalami perubahan alotropi lagi, berubah dari β-oktasulfur menjadi γ-sulfur,yang lagi-lagi diiringi dengan penurunan rapat jenis tetapi viskositasnya meningkat karena terjadi pembentukan polimer. Pada suhu yang lebih tinggi, viskositas menurun seiring terjadinya depolimerisasi. Leburan belerang diperkirakan berwarna merah tua di atas 200 °C (392 °F). Massa jenis belerang sekitar 2 g/cm³, tergantung pada alotropinya; seluruh alotropi stabilnya merupakan isolator listrik yang sangat baik.

Sifat kimia

Belerang terbakar dengan nyala api biru diiringi pembentukan belerang disulfida, yang memiliki bau yang mencekik dan mengganggu. Belerang tidak larut dalam air tetapi larut dalam karbon disulfida dan, pada kadar yang lebih rendah, dalam pelarut organik lainnya, seperti benzena dan toluena. Belerang memiliki energi ionisasi pertama dan kedua berturut-turut 999,6 dan 2252 kJ/mol. Meskipun demikian, belerang jarang dijumpai berada pada tingkat oksidasi +2, lebih umum pada tingkat oksidasi +4 dan +6. Energi ionisasi keempat dan keenam adalah 4556 dan 8495,8&nbspbkJ/mol, besarnya nilai tersebut disebabkan oleh transfer elektron antar orbital; keadaan ini hanya stabil dengan oksidator kuat seperti fluor, oksigen, dan klorin. Belerang bereaksi dengan hampir semua unsur lainnya kecuali gas mulia, bahkan dengan logam iridium yang terkenal tidak reaktif (menghasilkan iridium disulfida). Beberapa reaksi tersebut membutuhkan suhu tinggi.

Isotop

Artikel utama: Isotop belerang

Belerang diketahui memiliki 23 isotop, empat di antaranya adalah isotop stabil: ³²S (94,99%±0,26%), ³³S (0,75%±0,02%), ³⁴S (4,25%±0,24%), dan ³⁶S (0,01%±0,01%). Selain ³⁵S, dengan waktu paruh 87 hari dan terbentuk dalam spalasi sinar kosmis dari ⁴⁰Ar, isotop belerang radioaktif mempunyai waktu paruh kurang dari 3 jam.

Ketika mineral sulfida diendapkan, kesetimbangan isotop antara padatan dan cairan dapat menyebabkan perbedaan kecil pada nilai δ34S mineral ko-genetik. Perbedaan antar mineral dapat digunakan untuk memperkirakan suhu kesetimbangan. δ13C dan δ34S dari mineral karbonat dan sulfida yang hadir berdampingan dapat digunakan untuk menentukan pH dan fugasitas oksigen dari fluida yang mengandung bijih selama pembentukan bijih.

Pada kebanyakan ekosistem hutan, sebagian besar sulfat diperoleh dari atmosfer; pelapukan mineral bijih dan evaporit menyumbang sebagian Belerang. Belerang dengan komposisi isotop yang khas telah digunakan untuk mengidentifikasi sumber polusi, dan belerang yang diperkaya telah ditambahkan sebagai pelacak dalam studi hidrologi. Perbedaan kelimpahan alami dapat digunakan dalam sistem yang memiliki variasi komponen ekosistem ³⁴S yang memadai. Danau Rocky Mountain yang diduga didominasi oleh sulfat yang bersumber dari atmosfer telah diketahui memiliki nilai karakteristik ³⁴S dari danau yang diyakini didominasi oleh sumber aliran air sulfat.

Keterjadian alami

Tong berisi belerang sedang dimuat ke atas gerbong kereta, Freeport Sulphur Co., Hoskins Mound, Texas (1943)

Sebagian besar warna kuning dan oranye Io disebabkan oleh unsur belerang dan senyawa belerang yang diendapkan oleh gunung berapi aktif.

Seorang pria membawa bongkahan belerang dari Kawah Ijen, salah satu gunung berapi di Jawa Timur, Indonesia, 2009

³²S terbentuk di dalam bintang pejal, pada suatu kedalaman dengan suhu lebih dari 2,5×10⁹ K, melalui fusi satu inti silikon dengan satu inti helium. Oleh karena reaksi nuklir ini merupakan bagian dari proses alfa yang menghasilkan unsur-unsur berkelimpahan, belerang adalah unsur terbanyak ke-10 di alam semesta.

Belerang, biasanya sebagai sulfidanya, hadir dalam banyak jenis meteorit. Kondrit biasa mengandung rata-rata 2,1% belerang, dan kondrit berkarbon dapat mengandung belerang hingga 6,6%. Belerang umumnya hadir sebagai troilit (FeS), tetapi ada perkecualian, yaitu kondrit berkarbon mengandung belerang bebas, sulfat, dan senyawa belerang lainnya. Warna khas Io, bulan vulkanik Jupiter, dikaitkan dengan berbagai bentuk belerang cair, padat, dan gas.

Belerang adalah unsur paling banyak kelima di Bumi. Belerang elementer dapat dijumpai di sekitar daerah mata air panas dan gunung berapi di berbagai belahan dunia, terutama sepanjang Cincin Api Pasifik; sehingga deposit vulkanik semacam itu saat ini ditambang di Indonesia, Chili, dan Jepang. Deposit-deposit ini berupa polikristalin, dengan ukuran kristal terbesar yang pernah didokumentasikan mencapai 22×16×11 cm. Dalam catatan sejarah, Sisilia tadinya adalah sumber utama belerang dalam Revolusi Industri. Danau belerang cair bediameter hingga ~200 m telah ditemukan di dasar laut, yang dikaitkan dengan gunung api bawah laut, pada kedalaman di mana titik didih air lebih tinggi daripada titik leleh belerang.

Belerang asli disintesis oleh bakteri anaerob yang bekerja pada mineral sulfat seperti gipsum di kubah garam. Deposit yang signifikan dalam kubah garam terjadi di sepanjang pantai Teluk Meksiko, dan di evaporit di Eropa Timur dan Asia Barat. Belerang asli dapat dihasilkan dari proses geologi saja. Deposit belerang berbasis fosil dari kubah garam pernah menjadi dasar produksi komersial di Amerika Serikat, Rusia, Trukmenistan, dan Ukraina. Saat ini, produksi komersial tetapi dilakukan di tambang Osiek di Polandia. Sumber semacam itu sekarang menjadi prioritas kedua, dan kebanyakan sudah ditinggalkan.

Senyawa belerang yang umum terjadi secara alami di antaranya adalah mineral sulfida, seperti pirit (besi sulfida), sinabar (merkuri sulfida), galena (timbal sulfida), sfalerit (seng sulfida), dan stibnit (antimon sulfida); dan mineral sulfat, seperti gipsum (kalsium sulfat), alunit (kalium aluminium sulfat), dan barit (barium sulfat). Pada planet Bumi, seperti pada satelit Jupiter Io, belerang elementer terjadi secara alami pada emisi vulkanik, termasuk emisi dari ventilasi hidrotermal.

Senyawa

Lihat pula Kategori: Senyawa belerang

Keadaan oksidasi belerang umumnya berada pada rentang −2 sampai +6. Belerang membentuk senyawa stabil denan seluruh unsur keculi gas mulia.

Alotropi

Artikel utama: Alotropi belerang

Struktur molekul siklooktasulfur, S₈

Belerang membentuk lebih dari 30 alotropi padat, lebih banyak daripada unsur lainnya. Selain S₈, diketahui pula beberapa cincin lainnya. Dengan mengurangi satu atom dari mahkota menghasilkan S₇, yang memiliki warna kuning lebih tajam daripada S₈. Analisis HPLC "unsur belerang" menunjukkan campuran kesetimbangan terutama S₈, dan ada juga S₇ serta sejumlah kecil S₆. Cincin yang lebih besar telah berhasil dibuat, termasuk S₁₂ dan S₁₈.

Belerang amorf atau "plastik" dibuat melalui pendinginan cepat lelehan belerang—misalnya, dengan menuangkannya ke dalam air dingin. Studi kristalografi sinar-X menunjukkan bahwa bentuk amorf dapat memiliki struktur heliks dengan delapan atom per putaran. Molekul polimer berpilin panjang membentuk zat elastis berwarna kecoklatan, dan pada fase ruahnya, bentuk ini terasa seperti karet mentah. Bentuk ini bersifat metastabil pada suhu ruang dan secara bertahap kembali ke alotropi molekul kristalnya, yang tidak lagi elastis. Proses ini terjadi dalam jangka waktu jam atau hari, tetapi dapat dipercepat dengan menggunakan katalis.

Polikation dan polianion

Lapis lazuli memiliki warna biru karena kandungan anion radikal trisulfur (S−3)

Belerang polikation, S2+8, S2+4, dan S2+16 dihasilkan ketika belerang direaksikan dengan oksidator lemah dalam larutan asam kuat. Larutan berwarna yang dihasilkan dengan melarutkan belerang dalam asam sulfat pekat berasap pertama kali dilaporkan pada tahun 1804 oleh C.F. Bucholz, tetapi penyebab munculnya warna dan struktur polikation yang terlibat baru ditentukan pada akhir 1960-an. S2+8 berwarna biru tua, S2+4 kuning, dan S2+16 merah.

Anion radikal S−3 menghasilkan warna biru mineral lapis lazuli.

Dua rantai belerang paralel tumbuh di dalam tabung nano karbon (CNT) berdinding tunggal (a). Rantai S di dalam CNT berdinding ganda zig-zag (b) dan lurus (c).

Sulfida

Perlakuan belerang dengan hidrogen menghasilkan hidrogen sulfida. Ketika dilarutkan dalam air, hidrogen sulfida bersifat asam lemah:

${\ce {H2S <=> HS- + H+}}$

Gas hidrogen sulfida dan anion hidrosulfida sangat beracun terhadap mamalia, karena mereka menghambat kapasitas angkut oksigen hemoglobin, dan sitokrom tertentu dengan cara yang serupa dengan sianida dan azida (lihat di bawah, pada bagian peringatan).

Reduksi unsur belerang menghasilkan polisulfida, yang mengandung rantai atom belerang yang diterminasi dengan pusat S⁻:

${\ce {2 Na + S8 -> Na2S8}}$

Reaksi ini menyoroti sifat khas belerang, yaitu kemampuannya melakukan katenasi (mengikat dirinya sendiri melalui pembentukan rantai). Protonasi anion polisulfida ini menghasilkan polisulfan, H₂S_x, dengan x = 2, 3, dan 4. Pada akhirnya, reduksi belerang menghasilkan garam sulfida:

${\ce {16 Na + S8 -> 8 Na2S}}$

Interkonversi spesies ini digunakan dalam baterai natrium–belerangbaterai natrium-belerang.

Oksida, asam okso, dan anion okso

Belerang oksida pada prinsipnya diperoleh melalui pembakaran belerang:

${\ce {S + O2 -> SO2}}$ (belerang dioksida)

${\ce {2 SO2 + O2 -> 2 SO3}}$ (belerang trioksida)

Telah diketahui beberapa belerang oksida; oksida yang kaya belerang termasuk belerang monoksida, disulfur monoksida, disulfur dioksida, dan oksida yang lebih tinggi, yang mengandung gugus peroxo.

Sulfur forms sulfur oxoacids, some of which cannot be isolated and are only known through the salts. Sulfur dioxide and sulfites (SO2−3) are related to the unstable sulfurous acid (H₂SO₃). Sulfur trioxide and sulfates (SO2−4) are related to sulfuric acid (H₂SO₄). Sulfuric acid and SO₃ combine to give oleum, a solution of pyrosulfuric acid (H₂S₂O₇) in sulfuric acid.

Thiosulfate salts (S₂O2−3), sometimes referred as "hyposulfites", used in photographic fixing (hypo) and as reducing agents, feature sulfur in two oxidation states. Sodium dithionite (Na₂S₂O₄), contains the more highly reducing dithionite anion (S₂O2−4).

Halides and oxyhalides

Several sulfur halides are important to modern industry. Sulfur hexafluoride is a dense gas used as an insulator gas in high voltage transformers; it is also a nonreactive and nontoxic propellant for pressurized containers. Sulfur tetrafluoride is a rarely used organic reagent that is highly toxic. Sulfur dichloride and disulfur dichloride are important industrial chemicals. Sulfuryl chloride and chlorosulfuric acid are derivatives of sulfuric acid; thionyl chloride (SOCl₂) is a common reagent in organic synthesis.

Pnictides

An important S–N compound is the cage tetrasulfur tetranitride (S₄N₄). Heating this compound gives polymeric sulfur nitride ((SN)_x), which has metallic properties even though it does not contain any metal atoms. Thiocyanates contain the SCN⁻ group. Oxidation of thiocyanate gives thiocyanogen, (SCN)₂ with the connectivity NCS-SCN. Phosphorus sulfides are numerous, the most important commercially being the cages P₄S₁₀ and P₄S₃.

Metal sulfides

Artikel utama: Sulfide mineral

The principal ores of copper, zinc, nickel, cobalt, molybdenum, and other metals are sulfides. These materials tend to be dark-colored semiconductors that are not readily attacked by water or even many acids. They are formed, both geochemically and in the laboratory, by the reaction of hydrogen sulfide with metal salts. The mineral galena (PbS) was the first demonstrated semiconductor and was used as a signal rectifier in the cat's whiskers of early crystal radios. The iron sulfide called pyrite, the so-called "fool's gold", has the formula FeS₂. Processing these ores, usually by roasting, is costly and environmentally hazardous. Sulfur corrodes many metals through tarnishing.

Organic compounds

Artikel utama: Organosulfur compounds

• Illustrative organosulfur compounds
• 
  Allicin, a chemical compound in garlic
• 
  (R)-cysteine, an amino acid containing a thiol group
• 
  Methionine, an amino acid containing a thioether
• 
  Diphenyl disulfide, a representative disulfide
• 
  Perfluorooctanesulfonic acid, a surfactant
• 
  Dibenzothiophene, a component of crude oil
• 
  Penicillin, an antibiotic where "R" is the variable group

Some of the main classes of sulfur-containing organic compounds include the following:

• Thiols or mercaptans (so called because they capture mercury as chelators) are the sulfur analogs of alcohols; treatment of thiols with base gives thiolate ions.
• Thioethers are the sulfur analogs of ethers.
• Sulfonium ions have three groups attached to a cationic sulfur center. Dimethylsulfoniopropionate (DMSP) is one such compound, important in the marine organic sulfur cycle.
• Sulfoxides and sulfones are thioethers with one and two oxygen atoms attached to the sulfur atom, respectively. The simplest sulfoxide, dimethyl sulfoxide, is a common solvent; a common sulfone is sulfolane.
• Sulfonic acids are used in many detergents.

Compounds with carbon-sulfur multiple bonds are uncommon, an exception being carbon disulfide, a volatile colorless liquid that is structurally similar to carbon dioxide. It is used as a reagent to make the polymer rayon and many organosulfur compounds. Unlike carbon monoxide, carbon monosulfide is stable only as an extremely dilute gas, found between solar systems.

Organosulfur compounds are responsible for some of the unpleasant odors of decaying organic matter. They are widely known as the odorant in domestic natural gas, garlic odor, and skunk spray. Not all organic sulfur compounds smell unpleasant at all concentrations: the sulfur-containing monoterpenoid (grapefruit mercaptan) in small concentrations is the characteristic scent of grapefruit, but has a generic thiol odor at larger concentrations. Sulfur mustard, a potent vesicant, was used in World War I as a disabling agent.

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 rubber, elemental sulfur is heated with the rubber to the point that chemical reactions form disulfide bridges between isoprene 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 vulcanization, after the Roman god of the forge and volcanism.

History

Antiquity

Pharmaceutical container for sulfur from the first half of the 20th century. From the Museo del Objeto del Objeto collection

Being abundantly available in native form, sulfur was known in ancient times and is referred to in the Torah (Genesis). English translations of the Bible commonly referred to burning sulfur as "brimstone", giving rise to the term "fire-and-brimstone" sermons, in which listeners are reminded of the fate of eternal damnation that await the unbelieving and unrepentant. It is from this part of the Bible that Hell is implied to "smell of sulfur" (likely due to its association with volcanic activity). According to the Ebers Papyrus, a sulfur ointment was used in ancient Egypt to treat granular eyelids. Sulfur was used for fumigation in preclassical Greece; this is mentioned in the Odyssey. Pliny the Elder discusses sulfur in book 35 of his Natural History, saying that its best-known source is the island of Melos. He mentions its use for fumigation, medicine, and bleaching cloth.

A natural form of sulfur known as shiliuhuang (石硫黄) was known in China since the 6th century BC and found in Hanzhong. By the 3rd century, the Chinese discovered that sulfur could be extracted from pyrite. Chinese Daoists were interested in sulfur's flammability and its reactivity with certain metals, yet its earliest practical uses were found in traditional Chinese medicine. A Song dynasty military treatise of 1044 AD described various formulas for Chinese black powder, which is a mixture of potassium nitrate (KNO₃), charcoal, and sulfur. It remains an ingredient of black gunpowder.

Various alchemical symbols for sulfur

Indian alchemists, practitioners of "the science of chemicals" (sanskrit rasaśāstra, रसशास्त्र), wrote extensively about the use of sulfur in alchemical operations with mercury, from the eighth century AD onwards. In the rasaśāstra tradition, sulfur is called "the smelly" (sanskrit gandhaka, गन्धक).

Early European alchemists gave sulfur a unique alchemical symbol, a triangle at the top of a cross. In traditional skin treatment, elemental sulfur was used (mainly in creams) to alleviate such conditions as scabies, ringworm, psoriasis, eczema, and acne. The mechanism of action is unknown—though elemental sulfur does oxidize slowly to sulfurous acid, which is (through the action of sulfite) a mild reducing and antibacterial agent.

Modern times

Above: Sicilian kiln used to obtain sulfur from volcanic rock (diagram from a 1906 chemistry book)

Right: Today sulfur is known to have antifungal, antibacterial, and keratolytic activity; in the past it was used against acne vulgaris, rosacea, seborrheic dermatitis, dandruff, pityriasis versicolor, scabies, and warts. This 1881 advertisement baselessly claims efficacy against rheumatism, gout, baldness, and graying of hair.

In 1777, Antoine Lavoisier helped convince the scientific community that sulfur was an element, not a compound.

Sulfur deposits in Sicily 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 Marseilles, France, for the production of sulfuric acid for use in the Leblanc process. In industrializing Britain, with the repeal of tariffs on salt in 1824, demand for sulfur from Sicily surged upward. The increasing British control and exploitation of the mining, refining, and transportation of the sulfur, coupled with the failure of this lucrative export to transform Sicily's backward and impoverished economy, led to the Sulfur Crisis of 1840, when King Ferdinand II 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.

In 1867, elemental sulfur was discovered in underground deposits in Louisiana and Texas. The highly successful Frasch process was developed to extract this resource.

In the late 18th century, furniture makers used molten sulfur to produce decorative inlays in their craft. Because of the sulfur dioxide produced during the process of melting sulfur, the craft of sulfur inlays was soon abandoned. 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. With the advent of the contact process, the majority of sulfur today is used to make sulfuric acid for a wide range of uses, particularly fertilizer.

Spelling and etymology

Sulfur is derived from the Latin word sulpur, which was Hellenized 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 Classical period. The true Greek word for sulfur, θεῖον, is the source of the international chemical prefix thio-. In 12th-century Anglo-French, 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. On the other hand, sulfur was the form chosen in the United States, whereas Canada uses both. The IUPAC adopted the spelling sulfur in 1990 or 1971, depending on the source cited, as did the Nomenclature Committee of the Royal Society of Chemistry in 1992, restoring the spelling sulfur to Britain. Oxford Dictionaries 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."

Production

Traditional sulfur mining at Ijen Volcano, East Java, Indonesia. This image shows the dangerous and rugged conditions the miners face, including toxic smoke and high drops, as well as their lack of protective equipment. The pipes over which they are standing are for condensing sulfur vapors.

Sulfur may be found by itself and historically was usually obtained in this form; pyrite has also been a source of sulfur. In volcanic regions in Sicily, in ancient times, it was found on the surface of the Earth, and the "Sicilian process" 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 carusi 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 Sicilian sulfur mines were horrific, prompting Booker T. Washington 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 sulphur mine in Sicily is about the nearest thing to hell that I expect to see in this life."

Sulfur recovered from hydrocarbons in Alberta, stockpiled for shipment in North Vancouver, British Columbia

Elemental sulfur was extracted from salt domes (in which it sometimes occurs in nearly pure form) until the late 20th century. Sulfur is now produced as a side product of other industrial processes such as in oil refining, in which sulfur is undesired. 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 Frasch process. 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 been employed in a major way anywhere in the world since 2002.

Today, sulfur is produced from petroleum, natural gas, and related fossil resources, from which it is obtained mainly as hydrogen sulfide. Organosulfur compounds, undesirable impurities in petroleum, may be upgraded by subjecting them to hydrodesulfurization, which cleaves the C–S bonds:

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 Claus process. This process entails oxidation of some hydrogen sulfide to sulfur dioxide and then the comproportionation of the two:

3 O₂ + 2 H₂S → 2 SO₂ + 2 H₂O

SO₂ + 2 H₂S → 3 S + 2 H₂O

Production and price (US market) of elemental sulfur

Owing to the high sulfur content of the Athabasca Oil Sands, stockpiles of elemental sulfur from this process now exist throughout Alberta, Canada. Another way of storing sulfur is as a binder for concrete, the resulting product having many desirable properties (see sulfur concrete). Sulfur is still mined from surface deposits in poorer nations with volcanoes, such as Indonesia, and worker conditions have not improved much since Booker T. Washington's days.

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 China (9.6), US (8.8), Canada (7.1) and Russia (7.1). Production has been slowly increasing from 1900 to 2010; the price was unstable in the 1980s and around 2010.

Applications

Sulfuric acid

Elemental sulfur is used mainly as a precursor to other chemicals. Approximately 85% (1989) is converted to sulfuric acid (H₂SO₄):

2 S + 3 O₂ + 2 H₂O → 2 H₂SO₄

Sulfuric acid production in 2000

In 2010, the United States produced more sulfuric acid than any other inorganic industrial chemical. 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.

Other important sulfur chemistry

Sulfur reacts directly with methane to give carbon disulfide, which is used to manufacture cellophane and rayon. One of the uses of elemental sulfur is in vulcanization of rubber, where polysulfide chains crosslink organic polymers. Large quantities of sulfites are used to bleach paper and to preserve dried fruit. Many surfactants and detergents (e.g. sodium lauryl sulfate) are sulfate derivatives. Calcium sulfate, gypsum, (CaSO₄·2H₂O) is mined on the scale of 100 million tonnes each year for use in Portland cement and fertilizers.

When silver-based photography was widespread, sodium and ammonium thiosulfate were widely used as "fixing agents". Sulfur is a component of gunpowder ("black powder").

Fertilizer

Sulfur is increasingly used as a component of fertilizers. The most important form of sulfur for fertilizer is the mineral calcium sulfate. Elemental sulfur is hydrophobic (not soluble in water) and cannot be used directly by plants. Over time, soil bacteria can convert it to soluble derivatives, which can then be used by plants. Sulfur improves the efficiency of other essential plant nutrients, particularly nitrogen and phosphorus. Biologically produced sulfur particles are naturally hydrophilic due to a biopolymer coating and are easier to disperse over the land in a spray of diluted slurry, resulting in a faster uptake.

The botanical requirement for sulfur equals or exceeds the requirement for phosphorus. It is an essential nutrient for plant growth, root nodule formation of legumes, and immunity and defense systems. Sulfur deficiency has become widespread in many countries in Europe. 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 acid rains.

Fine chemicals

A molecular model of the pesticide malathion

Organosulfur compounds are used in pharmaceuticals, dyestuffs, and agrochemicals. Many drugs contain sulfur; early examples being antibacterial sulfonamides, known as sulfa drugs. Sulfur is a part of many bacterial defense molecules. Most β-lactam antibiotics, including the penicillins, cephalosporins and monolactams contain sulfur.

Magnesium sulfate, known as Epsom salts when in hydrated crystal form, can be used as a laxative, a bath additive, an exfoliant, magnesium supplement for plants, or (when in dehydrated form) as a desiccant.

Fungicide and pesticide

Sulfur candle originally sold for home fumigation

Elemental sulfur is one of the oldest fungicides and pesticides. "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 powdery mildew diseases as well as black spot. In organic production, sulfur is the most important fungicide. It is the only fungicide used in organically farmed apple production against the main disease apple scab 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 from a dusting plane. Wettable sulfur is the commercial name for dusting sulfur formulated with additional ingredients to make it water miscible. It has similar applications and is used as a fungicide against mildew and other mold-related problems with plants and soil.

Elemental sulfur powder is used as an "organic" (i.e., "green") insecticide (actually an acaricide) against ticks and mites. A common method of application is dusting the clothing or limbs with sulfur powder.

A diluted solution of lime sulfur (made by combining calcium hydroxide with elemental sulfur in water) is used as a dip for pets to destroy ringworm (fungus), mange, and other dermatoses and parasites.

Sulfur candles of almost pure sulfur were burned to fumigate structures and wine barrels, but are now considered too toxic for residences.

Bactericide in winemaking and food preservation

Small amounts of sulfur dioxide gas addition (or equivalent potassium metabisulfite addition) to fermented wine to produce traces of sulfurous acid (produced when SO₂ reacts with water) and its sulfite salts in the mixture, has been called "the most powerful tool in winemaking". After the yeast-fermentation stage in winemaking, sulfites absorb oxygen and inhibit aerobic bacterial growth that otherwise would turn ethanol into acetic acid, souring the wine. Without this preservative step, indefinite refrigeration of the product before consumption is usually required. Similar methods go back into antiquity but modern historical mentions of the practice go to the fifteenth century. The practice is used by large industrial wine producers and small organic wine producers alike.

Sulfur dioxide and various sulfites have been used for their antioxidant antibacterial preservative properties in many other parts of the food industry. The practice has declined since reports of an allergy-like reaction of some persons to sulfites in foods.

Pharmaceuticals

Artikel utama: Sulfur (pharmacy)

Sulfur (specifically octasulfur, S₈) is used in pharmaceutical skin preparations for the treatment of acne and other conditions. It acts as a keratolytic agent and also kills bacteria, fungi, scabies mites, and other parasites. Precipitated sulfur and colloidal sulfur are used, in form of lotions, creams, powders, soaps, and bath additives, for the treatment of acne vulgaris, acne rosacea, and seborrhoeic dermatitis.

Common adverse effects include irritation of the skin at the application site, such as dryness, stinging, itching and peeling.

Furniture

Artikel utama: Sulfur inlay

Sulfur can be used to create decorative inlays in wooden furniture. After a design has been cut into the wood, molten sulfur is poured in and then scraped away so it is flush. Sulfur inlays were particularly popular in the late 18th and early 19th centuries, notably amongst Pennsylvania German cabinetmakers. The practice soon died out, as less toxic and flammable substances were substituted. However, some modern craftsmen have occasionally revived the technique in the creation of replica pieces.

Biological role

Protein and organic cofactors

Sulfur is an essential component of all living cells. It is either the seventh or eighth most abundant element in the human body by weight, about equal in abundance to potassium, and slightly greater than sodium and chlorine. A 70 kg (150 pon) human body contains about 140 grams of sulfur.

In plants and animals, the amino acids cysteine and methionine contain most of the sulfur, and the element is present in all polypeptides, proteins, and enzymes that contain these amino acids. In humans, methionine is an essential amino acid that must be ingested. However, save for the vitamins biotin and thiamine, cysteine and all sulfur-containing compounds in the human body can be synthesized from methionine. The enzyme sulfite oxidase is needed for the metabolism of methionine and cysteine in humans and animals.

Disulfide bonds (S-S bonds) between cysteine residues in peptide chains are very important in protein assembly and structure. These covalent bonds between peptide chains confer extra toughness and rigidity. For example, the high strength of feathers and hair is due in part to the high content of S-S bonds with cysteine and sulfur. Eggs are high in sulfur to nourish feather formation in chicks, and the characteristic odor of rotting eggs is due to hydrogen sulfide. The high disulfide bond content of hair and feathers contributes to their indigestibility and to their characteristic disagreeable odor when burned.

Homocysteine and taurine are other sulfur-containing acids that are similar in structure, but not coded by DNA, and are not part of the primary structure of proteins. Many important cellular enzymes use prosthetic groups ending with -SH moieties to handle reactions involving acyl-containing biochemicals: two common examples from basic metabolism are coenzyme A and alpha-lipoic acid. Two of the 13 classical vitamins, biotin, and thiamine, contain sulfur, with the latter being named for its sulfur content.

In intracellular chemistry, sulfur operates as a carrier of reducing hydrogen and its electrons for cellular repair of oxidation. Reduced glutathione, a sulfur-containing tripeptide, is a reducing agent through its sulfhydryl (-SH) moiety derived from cysteine. The thioredoxins, a class of small proteins essential to all known life, use neighboring pairs of reduced cysteines to work as general protein reducing agents, with similar effect.

Methanogenesis, the route to most of the world's methane, is a multistep biochemical transformation of carbon dioxide. This conversion requires several organosulfur cofactors. These include coenzyme M, CH₃SCH₂CH₂SO₃⁻, the immediate precursor to methane.

Metalloproteins and inorganic cofactors

Metalloproteins in which the active site is a transition metal complex bound to sulphur atoms are essential components of enzymes involved in electron transfer processes. Examples include blue copper proteins and nitrous oxide reductase. The function of these enzymes is dependent on the fact that the transition metal ion can undergo redox reactions.Other examples include iron–sulfur clusters as well as many copper, nickel, and iron proteins. Most pervasive are the ferrodoxins, which serve as electron shuttles in cells. In bacteria, the important nitrogenase enzymes contains an Fe–Mo–S cluster and is a catalyst that performs the important function of nitrogen fixation, 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.

Sulfur metabolism and the sulfur cycle

Artikel utama: Sulfur metabolism dan Sulfur cycle

The sulfur cycle was the first of the biogeochemical cycles to be discovered. In the 1880s, while studying Beggiatoa (a bacterium living in a sulfur rich environment), Sergei Winogradsky found that it oxidized hydrogen sulfide (H₂S) as an energy source, forming intracellular sulfur droplets. Winogradsky referred to this form of metabolism as inorgoxidation (oxidation of inorganic compounds). He continued to study it together with Selman Waksman until the 1950s.

Sulfur oxidizers can use as energy sources reduced sulfur compounds, including hydrogen sulfide, elemental sulfur, sulfite, thiosulfate, and various polythionates (e.g., tetrathionate). They depend on enzymes such as sulfur oxygenase and sulfite oxidase to oxidize sulfur to sulfate. Some lithotrophs can even use the energy contained in sulfur compounds to produce sugars, a process known as chemosynthesis. Some bacteria and archaea use hydrogen sulfide in place of water as the electron donor in chemosynthesis, a process similar to photosynthesis that produces sugars and utilizes oxygen as the electron acceptor. The photosynthetic green sulfur bacteria and purple sulfur bacteria and some lithotrophs use elemental oxygen to carry out such oxidization of hydrogen sulfide to produce elemental sulfur (S⁰), oxidation state= 0. Primitive bacteria that live around deep ocean volcanic vents oxidize hydrogen sulfide in this way with oxygen; the giant tube worm is an example of a large organism that uses hydrogen sulfide (via bacteria) as food to be oxidized.

The so-called sulfate-reducing bacteria, 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). The hydrogen sulfide produced by these bacteria is responsible for some of the smell of intestinal gases (flatus) and decomposition products.

Sulfur is absorbed by plants roots from soil as sulfate and transported as a phosphate ester. Sulfate is reduced to sulfide via sulfite before it is incorporated into cysteine and other organosulfur compounds.

SO₄²⁻ → SO₃²⁻ → H₂S → cysteine → methionine

Precautions

Agung.karjono/Bak pasir/Timbal(II) nitrat

Bahaya
Piktogram GHS
Keterangan bahaya GHS	{{{value}}}
Pernyataan bahaya GHS	H315

Effect of acid rain on a forest, Jizera Mountains, Czech Republic

Elemental sulfur is non-toxic, as are most of the soluble sulfate salts, such as Epsom salts. Soluble sulfate salts are poorly absorbed and laxative. When injected parenterally, they are freely filtered by the kidneys and eliminated with very little toxicity in multi-gram amounts.

When sulfur burns in air, it produces sulfur dioxide. In water, this gas produces sulfurous acid and sulfites; sulfites are antioxidants that inhibit growth of aerobic bacteria and a useful food additive in small amounts. At high concentrations these acids harm the lungs, eyes, or other tissues. In organisms without lungs such as insects or plants, sulfite in high concentration prevents respiration.

Sulfur trioxide (made by catalysis from sulfur dioxide) and sulfuric acid are similarly highly acidic and corrosive in the presence of water. Sulfuric acid is a strong dehydrating agent that can strip available water molecules and water components from sugar and organic tissue.

The burning of coal and/or petroleum by industry and power plants generates sulfur dioxide (SO₂) that reacts with atmospheric water and oxygen to produce sulfuric acid (H₂SO₄) and sulfurous acid (H₂SO₃). These acids are components of acid rain, lowering the pH of soil and freshwater bodies, sometimes resulting in substantial damage to the environment and chemical weathering of statues and structures. Fuel standards increasingly require that fuel producers extract sulfur from fossil fuels to prevent acid rain formation. This extracted and refined sulfur represents a large portion of sulfur production. In coal-fired power plants, flue gases are sometimes purified. More modern power plants that use synthesis gas extract the sulfur before they burn the gas.

Hydrogen sulfide is as toxic as hydrogen cyanide, and kills by the same mechanism (inhibition of the respiratory enzyme cytochrome oxidase), though hydrogen sulfide is less likely to cause surprise poisonings from small inhaled amounts because of its disagreeable odor. Hydrogen sulfide quickly deadens the sense of smell and a victim may breathe increasing quantities without noticing the increase until severe symptoms cause death. Dissolved sulfide and hydrosulfide salts are toxic by the same mechanism.

See also

• Stratospheric sulfur aerosols
• Sulfur assimilation
• Ultra-low sulfur diesel

Further reading

Sigel, Astrid; Freisinger, Eva; Sigel, Roland K.O., ed. (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. hlm. xlv+455. ISBN 978-3-11-058889-7. 

External links

• Sulfur at The Periodic Table of Videos (University of Nottingham)
• Atomic Data for Sulfur, NIST Physical Measurement Laboratory
• Sulfur phase diagram, Introduction to Chemistry for Ages 13–17
• Crystalline, liquid and polymerization of sulfur on Vulcano Island, Italy
• Sulfur and its use as a pesticide
• The Sulphur Institute
• Nutrient Stewardship and The Sulphur Institute