Dictionary:

sulfur

  (sŭl'fər)

A pale yellow nonmetallic element occurring widely in nature in several free and combined allotropic forms. It is used in black gunpowder, rubber vulcanization, the manufacture of insecticides and pharmaceuticals, and in the preparation of sulfur compounds such as hydrogen sulfide and sulfuric acid. Atomic number 16; atomic weight 32.066; melting point (rhombic) 112.8°C, (monoclinic) 119.0°C; boiling point 444.6°C; specific gravity (rhombic) 2.07, (monoclinic) 1.957; valence 2, 4, 6.

To treat with sulfur or a compound of sulfur.

[Middle English, from Anglo-Norman sulfre, from Latin sulfur.]

A chemical element, S, atomic number 16, and atomic weight 32.064. The atomic weight reflects the fact that sulfur is composed of the isotopes ³²S (95.1%), ³³S (0.74%), ³⁴S (4.2%), and ³⁶S (0.016%). The ratios of the various isotopes vary slightly but measurably according to the history of the sample. By virtue of its position in the periodic table, sulfur is classified as a main-group element. See also Periodic table.

The chemistry of sulfur is more complex than that of any other elemental substance, because sulfur itself exists in the largest variety of structural forms. At room temperature, all the stable forms of sulfur are molecular; that is, the individual atoms aggregate into discrete molecules, which in turn pack together to form the solid material. In contrast, other elements near sulfur in the periodic table normally exist as polymers (silicon, phosphorus, arsenic, selenium, tellurium) or as diatomic molecules (oxygen, nitrogen, chlorine). Selenium and phosphorus can exist as molecular solids, but the stable forms of these elements are polymeric.

At room temperature the most stable form of sulfur is the cyclic molecule S₈. The molecule adopts a crownlike structure, consisting of two interconnected layers of four sulfur atoms each. The SS bond distances are 0.206 nanometer and the SSS bond angles are 108°. Three allotropes are known for cyclo-S₈. The most common form is orthorhombic α-sulfur, which has a density of 2.069 g/cm³ (1.200 oz/in.³) and a hardness of 2.5 on the Mohs scale. It is an excellent electrical insulator, with a room temperature conductivity of 10¹⁸ ohm⁻¹ cm⁻¹. Sublimed sulfur and “flowers” of sulfur are generally composed of α-S₈. Sulfur is quite soluble in carbon disulfide (CS₂; 35.5/100 g or 1.23 oz/3.52 oz at 25°C or 77°F), poorly soluble in alcohols, and practically insoluble in water. At 95.3°C (203°F), sulfur changes into the monoclinic β allotrope. This form of sulfur also consists of cyclic S₈ molecules, but it has a slightly lower density at 1.94–2.01 g/cm³ (1.12–1.16 oz/in.³). A third allotrope containing S₈ is triclinic γ-sulfur. The β and γ allotropes of sulfur slowly revert to the α form at room temperature. Crystals of sulfur are yellow and have an absorption maximum in the ultraviolet at 285 nm, which shifts to higher energy as the temperature decreases. At low temperatures, S₈ is colorless. Even at room temperature, however, finely powdered sulfur can appear to be nearly white.

The best-studied system is α-S₈, which converts to the β form at 90°C (194°F), which then melts at 120°C (248°F) to give a golden yellow liquid. If this melt is quickly recooled, it refreezes at 120°C (248°F), thus indicating that it consists primarily of S₈ molecules. If the melt is maintained longer at 120°C (248°F), then the freezing point is lowered about 5°C (9°F), indicating the formation of about 5% of other rings and some polymer. At 159.4°C (318.9°F), the melt suddenly assumes a red-brown color. Over the range 159.4–195°C (318.9–383°F), the viscosity of the melt increases 10,000-fold before gradually decreasing again. This behavior is very unusual, since the viscosity of most liquids decreases with increasing temperature. The strong temperature dependence of the viscosity is due to the polymerization and eventual depolymerization of sulfur. Polymeric sulfur retains its elastomeric character even after being cooled to room temperature. There are several polymeric forms of sulfur, but all of them revert to α-S₈ after a few hours.

Sublimination of S₈ occurs when it is maintained in a vacuum at a temperature below its melting point. It vaporizes at 444.61°C (832.30°F). Below 600°C (1110°F), the predominant species in the gas are S₈ followed by S₇ and S₆. Above 720°C (1328°F), violet S₂ is the major species.

Principal inorganic compounds

Hydrogen sulfide (H₂S) is the most important compound that contains only sulfur and hydrogen. It is a gas at room temperature with a boiling point of −61.8°C (−79.2°F) and a freezing point of −82.9°C (−117°F). The low boiling point of hydrogen sulfide is attributed to the weakness of intermolecular S···H hydrogen bonding; the O···H hydrogen bond is much stronger, as evidenced by the high boiling point of water. Gaseous hydrogen sulfide is 1.19 times more dense than air, and air-H₂S mixtures are explosive. Hydrogen sulfide has a strong odor similar to that of rotten eggs; its odor is detectable at concentrations below 1 microgram/m³. At high concentrations, H₂S has a paralyzing effect on the olfactory system, which is very hazardous because H₂S is even more toxic than carbon monoxide (CO).

The most common compound that contains only carbon and sulfur is carbon disulfide (CS₂). Carbon disulfide molecules are linear, consisting of two sulfur atoms connected to a central carbon atom. Carbon disulfide is a toxic, highly flammable, and volatile liquid that melts at −111°C (−168°F) and boils at 46°C (115°F). Commercial carbon disulfide has a strong unpleasant odor due to impurities. It is manufactured from methane and elemental sulfur and is used for the production of carbon tetrachloride, rayon, and cellophane. Structurally related to carbon disulfide is carbonyl sulfide (SCO), which forms from carbon monoxide and elemental sulfur. The chlorination of CS₂ gives Cl₃CSCl, which can be reduced by H₂S to thiophosphene, CSCl₂. Thiophosgene (CSCl₂) [boiling point 73°C or 163°F] is a planar molecule with the carbon at the center of a triangle defined by the sulfur and two chlorine atoms. Thiocyanate, the linear anion NCS⁻, is prepared by the reaction of cyanide (CN) with elemental sulfur.

Several sulfur oxides exist, but the dioxide and trioxide are of preeminent importance. Sulfur dioxide (SO₂) is a colorless gas that boils at −10.02°C (113.97°F) and freezes at −75.46°C (−103.8°F). The density of liquid sulfur dioxide at −10°C (14°F) is 1.46 g/cm³ (0.84 oz/in.³). Liquid sulfur dioxide is an excellent solvent. The sulfur dioxide molecule is bent, with an OSO angle of 119°.

Sulfur trioxide (SO₃) is a planar molecule that is a liquid at room temperature that exists in equilibrium with a cyclic trimeric structure known as β-SO₃. When β-SO₃, actually S₃O₉, is treated with traces of water, it converts to either of two polymeric forms referred to as γ- and α-sulfur trioxide. These are fibrous materials, proposed to have the formula (SO₃)_xH₂, where x is in the thousands. Sulfur trioxide is prepared by the oxidation of sulfur dioxide, although at very high temperatures this reaction reverses. Exposure of sulfur trioxide to water yields sulfuric acid (H₂SO₄); exposure of SO₃ to sulfuric acid yields disulfuric acid (H₂S₂O₇). See also Sulfuric acid.

Chlorine and sulfur react to give a family of compounds with the general formula S_xCl₂, several members of which have been obtained in pure form. The structures of these compounds are based on an atom or chain of sulfur atoms terminated with Cl. Sulfur monochloride (S₂Cl₂), also known as sulfur monochloride, is the most widely available of the series. It is a yellow oil that boils at 138°C (280°F), and reacts with chlorine in the presence of iron(III) chloride (FeCl₃) catalyst to give sulfur dichloride (SC₂), which is a red volatile liquid with a boiling point of 59°C (138°F). Treatment of sulfur dichloride with sodium fluoride (NaF) gives SF₄.

Thionyl chloride (OSCl₂) is a colorless reactive compound with a boiling point of 76°C (169°F); it is used to convert hydroxy compounds to chlorides. Important applications include the preparation of anhydrous metal halides and alkyl halides. Sulfuryl chloride (O₂SCl₂; boiling point 69°C or 156°F) is used as a source of chlorine.

Organosulfur compounds

This family of compounds contains carbon, hydrogen, and sulfur, and it is a particularly vast area of sulfur chemistry. Thiols, also known as mercaptans, feature the linkage CSH. Mercaptans are foul-smelling compounds. They are the sulfur analogs of alcohols, but they are more volatile. They can be prepared by the action of hydrogen sulfide (H₂S) on olefins. Deprotonation of thiols gives thiolate anions, which form stable compounds with many heavy metals. Thiols and especially thiolates can be oxidized to form disulfides (persulfides), which have the connectivity of CSSC. The organic persulfides are also related to organic polysulfides, which have chains of sulfur atoms terminated with carbon. The introduction of such mono-, di-, and polysulfide linkages is the basis of the vulcanization process, which imparts desirable mechanical properties to natural or synthetic polyolefin rubbers. This is accomplished by heating the polymer with sulfur in the presence of a zinc catalyst. See also Rubber.

Thioethers, also known as organic sulfides, feature the connectivity CSC and are often prepared from the reaction of thiolates and alkyl halides. Like mercaptans, thioethers often have strong unpleasant odors, but they are also responsible for the pleasant odors of many foods and perfumes. They are intentionally introduced at trace levels in order to impart an odor to gaseous hydrocarbon fuels. The reaction of alkyl dihalides and sodium polysulfides affords organic polysulfide polymers known as thiokols.

There are many organic sulfur oxides; prominent are sulfonic acids (RSO₃H), which are the organic derivatives of sulfuric acid. These compounds are prepared by the oxidation of thiols as well as by treatment of benzene derivatives with sulfuric acid, for example, benzene sulfonic acid. Most detergents are salts of sulfonic acids.

Biochemistry

Sulfur is required for life. Typical organisms contain 2% sulfur dry weight. Three amino acids contain sulfur, as do many prosthetic groups in enzymes. Some noteworthy sulfur compounds include the disulfide lipoic acid, the thioethers biotin and thiamine (vitamin B₁), and the thiol coenzyme A. Sulfide ions, S²⁻, are found incorporated in metalloproteins and metalloenzymes such as the ferredoxins, nitrogenases, and hydrogenases. See also Amino acids; Enzyme; Protein.

Many bacterial species obtain energy by the oxidations of sulfides. Bacteria of the genus Thiobacillus couple the conversion of carbon dioxide (CO₂) to carbohydrates to the aerobic oxidation of mineral sulfides to sulfuric acid. This activity can be turned to good use for leaching low-grade mineral ores. Often, however, the sulfuric acid runoff (such as in mines or sewers) has negative environmental consequences. The purple and green bacteria as well as the blue-green algae are remarkable because they are photosynthetic but anaerobic; they oxidize sulfide, not water (as do most photosynthetic organisms). Depending on the species, the sulfur produced in this energy-producing pathway can accumulate inside or outside the cell wall. See also Bacterial physiology and metabolism; Photosynthesis.

Minerals

Sulfide minerals are among the most important ores for several metals. These compounds are two- or three-dimensional polymers containing interconnected metal cations and sulfide S²⁻ or persulfido S₂²⁻ anions. In general, metal sulfides are darkly colored, often black, and they are not soluble in water. They can sometimes be decomposed by using strong acids, with liberation of hydrogen sulfide. Certain sulfides will also dissolve in the presence of excess sulfide or polysulfide ions.

Pyrites (FeS₂), also known as iron pyrites or fool's gold, are the most common sulfide minerals and can be obtained as very large crystals that have a golden luster. Sphalerite (zinc blende; ZnS) and galena (PbS) are major sources of zinc and lead. Orange cinnabar (HgS) and yellow greenockite (CdS) are the major ores for mercury and cadmium, respectively. Molybdenite (MoS₂) is the major ore of molybdenum.

The sulfur content of fossil fuels results from the sulfur in the ancient organisms as well as from subsequent incorporation of mineral sulfur into the hydrocarbon matrix. Gaseous fossil fuels are often contaminated with hydrogen sulfide, which is an increasingly important source of sulfur. Organic derivatives containing the CSC linkage are primarily responsible for the sulfur content of petroleum and coal. The so-called organic sulfur in petroleum can be removed by hydrodesulfurization catalysis, involving reaction with hydrogen over a molybdenum catalyst, to give hydrocarbons and hydrogen sulfide.

A nonmetallic, multivalent, tasteless, odorless chemical element that occurs abundantly in yellow crystalline form or in masses, especially in volcanic areas. Its atomic number is 16, and its atomic weight is 32.064. It has wide use in industry. Sulfur has been used in the treatment of gout, rheumatism, and bronchitis and as a mild laxative.

Description

Sulfur is a homeopathic remedy that is used to treat a variety of chronic or acute ailments. Elemental sulfur is present in all living tissues. Sulfur is often referred to as brimstone or flowers of sulfur.

Sulfur was used during biblical times as a remedy for skin disorders such as acne and scabies. Flowers of sulfur were burned to disinfect the rooms of persons with infectious disease. Sulfur was also taken with molasses as an internal cleanser, and was used to treat chronic bronchitis, constipation, and rheumatism. In the early 2000s the element is used in the manufacture of dyes, gunpowder, insecticides, fungicides, sulfuric acid, and rubber (as a hardening agent).

General Use

Sulfur is known as the king of homeopathic remedies because it has such a wide range of use. It works well with almost every other remedy and it acts on many different maladies and ailments. This polychrest has a deep, long-lasting effect on the body and is often used to bring out symptoms for further treatment. For this reason, sulfur is generally used to treat chronic ailments, although it is also used for acute conditions such as fevers and colds. Sulfur stimulates the body's natural healing powers, causing a general improvement of symptoms and sometimes causing new symptoms.

Homeopaths prescribe sulfur to treat skin ailments such as herpes, rashes, psoriasis, eczema, and acne. Other conditions helped by this remedy include arthritis, colds, coughs, flatulence, gastrointestinal disturbances, and headaches.

Ailments are caused by loss of vital fluids, drug abuse, overeating, becoming chilled, a change from cold to warm weather, effects of a debilitating disease, or from suppression of skin eruptions, hemorrhoids, or bodily discharges.

Typical sulfur patients are fair-haired, blue-eyed persons with red faces and lips that become cracked when they are ill. Their tongues often have a white coating and are red around the edges and on the tip. They are lean, stoop shouldered, lazy, averse to bathing, untidy, and disorderly. They don't pay attention to what they are wearing and often walk around with unmatched socks or missing ties. Patients are oversensitive to odors, especially their own, which are usually smelly.

Sulfur patients have often been called the "ragged philosopher," referring to the patient's disorderly ways. For instance, a sulfur type might be an inventor or scholar who is so absorbed in his project that he forgets to wash or change clothes. Patients are very bright but they spend a lot of time wandering about and studying strange subjects. They are dreamers and philosophers who lack perseverance to see their dreams through to fruition. They start many projects but complete few.

Physical symptoms include excessive thirst, swollen glands, profuse sweat, sensitivity to heat, burning pains, hot feet, boils, and acne. Symptoms generally appear on the left side. Bodily discharges are hot, burning, and sour smelling. The patient is extremely intolerable of the cold and other weather conditions. Arthritis, coughing, and hoarseness of the throat are all caused by damp weather or a change in weather. Skin conditions are often caused by a change in weather.

These patients are very sensitive to food and the times they eat. If a meal is delayed they may become nauseous and weak. At 10 A.M. or 11 A.M. they get an empty feeling in their stomachs and feel an intense hunger. Patients generally suffer from indigestion and other gastrointestinal disorders. They crave alcohol, sweets, spicy foods, fatty foods, and stimulants, but dislike milk and meat. Bread, cold food or drinks, fats, milk, and sweets aggravate their systems.

Mentally, patients are irritable, critical, discontented, impatient, depressed, quarrelsome, restless, hurried, anxious, easily offended, fearful, timid, absent-minded, sad, and weepy. They would rather not work; their symptoms often occur as a result of physical or mental exertion. The patient is always tired and lacks endurance. If made to stand for long periods of time he may feel faint.

Symptoms are aggravated by bathing, cold air, motion, itching, fasting, heat, milk, or standing. They are worse from 10-11 A.M., after eating, or in a stuffy room. Symptoms such as headaches may recur on a regular basis, i.e. every seven or ten days. Patients are worse after a long sleep and may not want to get up. All sulfur symptoms are better from fresh air and warm drinks.

Specific Indications

The backache typical of sulfur is aching, sore, and stiff. The back feels weak, tired, and bruised. It is worse from standing or walking, after sitting for long periods, during menstruation, or at night.

Sulfur patients catch colds easily and often. They cannot become overheated, remain in a cold place, or overexert themselves without catching a cold. The sulfur cold is accompanied by smelly nasal discharge, congestion, sneezing, eye inflammations, and an itchy, dry nose that, when blown, may bleed.

The sulfur cough is generally dry in the evening and loose in the morning. The chest is congested and the sides hurt from coughing. There is a feeling of dust in the throat. The discharge that is expectorated from the cough is of a greenish color. Patients may often awake from coughing. The cough is better when the patient is exposed to open air.

Diarrhea that occurs early in the morning around 5 A.M. is indicative of sulfur. The diarrhea is painless, slimy, watery, and foul smelling. It is accompanied by flatulence and is somewhat relieved by expulsion of the gas.

Earaches are accompanied by aching and lacerating pains. The earache is worse in the left ear. There is a ringing or roaring noise in the ear. The ears are frequently plugged and itchy.

Eye inflammations often accompany a cold. The eyes are itchy, watery, burning, dry, and sensitive to light. The eyelids itch in the daytime only. The patient may wake up with his eyes glued shut. Washing them, however, aggravates the condition.

Fatigue is worse in the evening or from talking. It is caused by sun exposure, hunger, or walking.

Fevers are hot and are accompanied by chills, shivering, and sweating. They are worse in the evening, after waking, or from mental exertion. The feet become extremely hot; therefore, the patient may stick his feet out from under the bedcovers to cool them.

The patient is very gassy and suffers from gas that smells like rotten eggs. The stomach is bloated and rumbles in irritation. The gas is often accompanied by a burning sensation and offensive-smelling stools.

Headaches are confined to the forehead or top of the head. They are hot and burning with hammering pains. These congestive headaches are caused by damp weather and are accompanied by nausea and vomiting. They often occur on Sunday and recur periodically. They are aggravated by motion, cold drinks, eating, bending over, blowing the nose, coughing, rising in the morning, and sneezing. Sometimes stars, zigzags, or other shapes will appear before the eyes.

Indigestion is common in sulfur patients. The patient can digest almost nothing, but he can't go long without eating. He has a weak stomach and a slow digestion. Stomach pains are sensitive to touch and a heavy feeling is present in the stomach. The patient is hungry at 10 A.M. and may need to eat to avoid feeling faint or weak. She may get a headache if she doesn't eat at that time. Indigestion is accompanied by sour belches, gas that smells rotten, bloating, and burning pains. It is worse after eating or from drinking milk.

Insomnia is caused by frequent waking in the early morning hours (3-5 A.M.). For this reason, the patient has a tendency to sleep late. However, no matter how much sleep the patient has, he always wakes up feeling tired. Short catnaps taken throughout the day refresh the patient. Patients are often unable to sleep before midnight.

Skin conditions are itchy, intense, and worse at night or in warm beds. The skin is itchy and burning and chaps easily. Ailments include herpes, rashes, acne, eczema, psoriasis, and dermatitis.

The sore throat is accompanied by swollen tonsils, burning pains, and a hoarse voice upon waking. The throat is dry and raw and may feel dusty. The throat is worse from coughing and swallowing.

Preparations

The homeopathic remedy is created by adding pure sulfur powder to a water/alcohol mixture or by grinding it with milk sugar. The mixture is then diluted and succussed to create the final preparation.

Sulfur is available at health food and drug stores in various potencies in the form of tinctures, tablets, and pellets.

Precautions

If symptoms do not improve after the recommended time period, a homeopath or health care practitioner should be consulted.

The recommended dose should not be exceeded.

Side Effects

There are no side effects but individual aggravations may occur.

Interactions

When taking any homeopathic remedy, use of peppermint products, coffee, or alcohol is discouraged. These products may cause the remedy to be ineffective.

Sulfur should not be taken immediately before lycopodium.

Resources

Books

Cummings, Stephen, M.D., and Ullman Dana, M.P.H., Everybody's Guide to Homeopathic Medicines. New York, NY: Jeremy P. Tarcher/Putnam, 1997.

Kent, James Tyler. Lectures on Materia Medica. Delhi, India: B. Jain Publishers, 1996.

[Article by: Jennifer Wurges]

(click to enlarge)
Sulfur crystals from Sicily (greatly enlarged) (credit: Courtesy of the Illinois State Museum; photograph, John H. Gerard)

Nonmetallic chemical element, chemical symbol S, atomic number 16. It is very reactive but occurs native in deposits, as well as combined in various ores (e.g., pyrite, galena, cinnabar); in coal, petroleum, and natural gas; and in the water in sulfur springs. Sulfur is the third most abundant constituent of minerals and one of the four most important basic chemical commodities. Pure sulfur, a tasteless, odourless, brittle yellow solid, occurs in several crystalline and amorphous allotropes, including brimstone and flowers of sulfur. It combines, with valence 2, 4, or 6, with nearly all other elements. Its most familiar compound is hydrogen sulfide, a poisonous gas that smells like rotten eggs. All metals except gold and platinum form sulfides, and many ores are sulfides. The oxides are sulfur dioxide and sulfur trioxide, which when dissolved in water make sulfurous acid and sulfuric acid, respectively. Several sulfur compounds with halogen elements are industrially important. Sodium sulfite (Na₂SO₃) is a reducing agent used to pulp paper and in photography. Organic compounds with sulfur include several amino acids, the sulfa drugs, and many insecticides, solvents, and substances used in making rubber and rayon.

For more information on sulfur, visit Britannica.com.

Environment

Associated worldwide with volcanic rocks, though the major commercially developed deposits are in sedimentary formations having been freed through the breakdown of sulfates such as gypsum or freed from H ₂ S.

All low-temperature natural crystals are orthorhombic. Remelted sulfur crystallizes in an unstable structure in the monoclinic system. Well-formed, translucent orthorhombic crystals are common in the developed sedimentary occurrences, usually as steep bipyramids, though sometimes tabular. Irregular cavernous and skeletal crystals are characteristic of the volcanic localities, where sulfur often sublimates from escaping volatile compounds, usually at temperatures lower than those condensing sal ammoniac and the like. Often in crusts without individualized crystals.

Light yellow when pure, sometimes amber when stained with hydrocarbons; some slaglike volcanic specimens are reddish from selenium contamination or grayish from arsenic contamination. Luster resinous; hardness 2; specific gravity 2.0-2.1; fracture conchoidal; cleavage basal, prismatic, and pyramidal. Brittle; translucent.

Sulfur, but often contaminated with clay or bitumen. Volcanic sulfur may contain selenium, arsenic, etc.

Melts at 108°C and burns with a blue flame and acrid fumes of SO ₂ . Insoluble in water and acids, dissolves in carbon disulfide. Not really fun to play with as the fumes are noxious and its acid (sulfuric, H ₂ SO ₄ ) very corrosive. Sulfur's physical states are interesting, for it melts to an amber liquid and, as it gets hotter, turns black, then yellow again when still hotter. However, it is not recommended that such experiments be undertaken outside of a well-equipped laboratory; chemists' laboratories keep fumes under a vented hood.

There are few minerals with which it would be confused. The ease of melting and the burning with noxious smell will readily distinguish it from any other substance.

Sulfur is a characteristic deposit of the later stages of volcanic activity. In New Zealand, and Middle and South America it has been quarried from the craters of volcanoes that are, or have been thought to be, extinct. Tiny sulfur crystals are found in cavities in some weathered sulfides. In galena it is associated in cavities with anglesite. It is constantly forming in crusts of small crystals at a fumarolic deposit south of San Felipe, Baja California, and in Steamboat Springs and elsewhere in Nevada. Masses were mined for the copper smelter at the Leviathan Mine on the California-Nevada border near the Yerington, Weed Flat, Nevada, copper mine.

However, the economically important deposits in Sicily, Spain, Poland, and along the Gulf Coast appear to have formed from gypsum (calcium sulfate) through a chemical reaction. The best specimens come from the Italian sulfur mines, where well-formed crystals up to 6 in. (15 cm) or more in length are found. Probably comparable ones occur in Louisiana and Texas, but because of the method of mining (the Frasch process of melting the sulfur in deeply buried rocks with superheated steam, and piping the amber liquid to the surface), the only American crystals available from the Gulf area come from 8-inch diamond-drill well cores. Large amounts of sulfur are extracted from high-sulfur fuel oils in the refining process and fumes for acid are recovered from smelters. Crystals have also been found in an asphaltic deposit in n. Italy, in a sulfur deposit in France at Malvesi, near Narbonne, with gypsum at Bex, Switzerland, near Cadiz, Spain, and in limestone in Michigan.

Sulfur is of great economic importance in fungicidal plant sprays, the vulcanization of rubber, and the production of sulfuric acid. It is a poor conductor of electricity and with friction becomes negatively charged. The warmth of the hand will cause crystals to expand at the surface and crack. Specimens should be kept out of sunlight, out of severe cold, and handled as little as possible.

An element with atomic number 16; symbol: S. Sulfur is common on the surface of Jupiter's moon Io.