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83-407: Addition of hydrogen sulfide or sulfide salts to a solution containing a lead salt, such as PbCl 2 , gives a black precipitate of lead sulfide. This reaction is used in qualitative inorganic analysis . The presence of hydrogen sulfide or sulfide ions may be tested using "lead acetate paper." Like the related materials PbSe and PbTe , PbS is a semiconductor . In fact, lead sulfide was one of

166-498: A double bond connects the atoms on either side of them. A triple bond may be expressed with three lines ( HC≡CH ) or three pairs of dots ( HC:::CH ), and if there may be ambiguity, a single line or pair of dots may be used to indicate a single bond. Molecules with multiple functional groups that are the same may be expressed by enclosing the repeated group in round brackets . For example, isobutane may be written (CH 3 ) 3 CH . This condensed structural formula implies

249-620: A structural formula is useful, as it illustrates which atoms are bonded to which other ones. From the connectivity, it is often possible to deduce the approximate shape of the molecule . A condensed (or semi-structural) formula may represent the types and spatial arrangement of bonds in a simple chemical substance, though it does not necessarily specify isomers or complex structures. For example, ethane consists of two carbon atoms single-bonded to each other, with each carbon atom having three hydrogen atoms bonded to it. Its chemical formula can be rendered as CH 3 CH 3 . In ethylene there

332-513: A characteristic foul odor of rotten eggs . Swedish chemist Carl Wilhelm Scheele is credited with having discovered the chemical composition of purified hydrogen sulfide in 1777. Hydrogen sulfide is toxic to humans and most other animals by inhibiting cellular respiration in a manner similar to hydrogen cyanide . When it is inhaled or its salts are ingested in high amounts, damage to organs occurs rapidly with symptoms ranging from breathing difficulties to convulsions and death. Despite this,

415-443: A chemical formula is complicated by being written as a condensed formula (or condensed molecular formula, occasionally called a "semi-structural formula"), which conveys additional information about the particular ways in which the atoms are chemically bonded together, either in covalent bonds , ionic bonds , or various combinations of these types. This is possible if the relevant bonding is easy to show in one dimension. An example

498-735: A correct structural formula. For example, ethanol may be represented by the condensed chemical formula CH 3 CH 2 OH , and dimethyl ether by the condensed formula CH 3 OCH 3 . These two molecules have the same empirical and molecular formulae ( C 2 H 6 O ), but may be differentiated by the condensed formulae shown, which are sufficient to represent the full structure of these simple organic compounds . Condensed chemical formulae may also be used to represent ionic compounds that do not exist as discrete molecules, but nonetheless do contain covalently bound clusters within them. These polyatomic ions are groups of atoms that are covalently bound together and have an overall ionic charge, such as

581-499: A different connectivity from other molecules that can be formed using the same atoms in the same proportions ( isomers ). The formula (CH 3 ) 3 CH implies a central carbon atom connected to one hydrogen atom and three methyl groups ( CH 3 ). The same number of atoms of each element (10 hydrogens and 4 carbons, or C 4 H 10 ) may be used to make a straight chain molecule, n - butane : CH 3 CH 2 CH 2 CH 3 . The alkene called but-2-ene has two isomers, which

664-472: A few weeks. Long-term, low-level exposure may result in fatigue , loss of appetite, headaches , irritability, poor memory, and dizziness . Chronic exposure to low level H 2 S (around 2 ppm ) has been implicated in increased miscarriage and reproductive health issues among Russian and Finnish wood pulp workers, but the reports have not (as of 1995) been replicated. Short-term, high-level exposure can induce immediate collapse, with loss of breathing and

747-476: A formula might be written using decimal fractions , as in Fe 0.95 O , or it might include a variable part represented by a letter, as in Fe 1− x O , where x is normally much less than 1. A chemical formula used for a series of compounds that differ from each other by a constant unit is called a general formula . It generates a homologous series of chemical formulae. For example, alcohols may be represented by

830-857: A high probability of death. If death does not occur, high exposure to hydrogen sulfide can lead to cortical pseudolaminar necrosis , degeneration of the basal ganglia and cerebral edema . Although respiratory paralysis may be immediate, it can also be delayed up to 72 hours. Inhalation of H 2 S resulted in about 7 workplace deaths per year in the U.S. (2011–2017 data), second only to carbon monoxide (17 deaths per year) for workplace chemical inhalation deaths. Treatment involves immediate inhalation of amyl nitrite , injections of sodium nitrite , or administration of 4-dimethylaminophenol in combination with inhalation of pure oxygen, administration of bronchodilators to overcome eventual bronchospasm , and in some cases hyperbaric oxygen therapy (HBOT). HBOT has clinical and anecdotal support. Hydrogen sulfide

913-472: A metallic conductor of electricity. When cooled below a critical temperature this high-pressure phase exhibits superconductivity . The critical temperature increases with pressure, ranging from 23 K at 100 GPa to 150 K at 200 GPa. If hydrogen sulfide is pressurized at higher temperatures, then cooled, the critical temperature reaches 203 K (−70 °C), the highest accepted superconducting critical temperature as of 2015. By substituting

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996-400: A molecular formula of C 6 H 14 , and (for one of its isomers, n-hexane) a structural formula CH 3 CH 2 CH 2 CH 2 CH 2 CH 3 , implying that it has a chain structure of 6 carbon atoms, and 14 hydrogen atoms. However, the empirical formula for hexane is C 3 H 7 . Likewise the empirical formula for hydrogen peroxide , H 2 O 2 , is simply HO , expressing

1079-482: A molecule than its empirical formula, but is more difficult to establish. In addition to indicating the number of atoms of each elementa molecule, a structural formula indicates how the atoms are organized, and shows (or implies) the chemical bonds between the atoms. There are multiple types of structural formulas focused on different aspects of the molecular structure. The two diagrams show two molecules which are structural isomers of each other, since they both have

1162-503: A number of other sugars , including fructose , galactose and mannose . Linear equivalent chemical names exist that can and do specify uniquely any complex structural formula (see chemical nomenclature ), but such names must use many terms (words), rather than the simple element symbols, numbers, and simple typographical symbols that define a chemical formula. Chemical formulae may be used in chemical equations to describe chemical reactions and other chemical transformations, such as

1245-432: A prefixed superscript in a chemical formula. For example, the phosphate ion containing radioactive phosphorus-32 is [ PO 4 ] . Also a study involving stable isotope ratios might include the molecule O O . A left-hand subscript is sometimes used redundantly to indicate the atomic number . For example, 8 O 2 for dioxygen, and 8 O 2 for the most abundant isotopic species of dioxygen. This

1328-400: A result of the action of sulfate-reducing bacteria . Hydrogen sulfide is produced by the human body in small quantities through bacterial breakdown in the intestinal tract of proteins containing sulfur; it therefore contributes to the characteristic odor of flatulence. It is also produced in the mouth ( halitosis ). A portion of global H 2 S emissions are due to human activity. By far

1411-510: A small part of sulfur with phosphorus and using even higher pressures, it has been predicted that it may be possible to raise the critical temperature to above 0 °C (273 K) and achieve room-temperature superconductivity . Hydrogen sulfide decomposes without a presence of a catalyst under atmospheric pressure around 1200 °C into hydrogen and sulfur. Hydrogen sulfide reacts with metal ions to form metal sulfides, which are insoluble, often dark colored solids. Lead(II) acetate paper

1494-453: A true structural formula, which is a graphical representation of the spatial relationship between atoms in chemical compounds (see for example the figure for butane structural and chemical formulae, at right). For reasons of structural complexity, a single condensed chemical formula (or semi-structural formula) may correspond to different molecules, known as isomers . For example, glucose shares its molecular formula C 6 H 12 O 6 with

1577-487: A variety of sulfide sources. In 2009, PbS nanoparticles have been examined for use in solar cells. PbS was one of the first materials used for electrical diodes that could detect electromagnetic radiation, including infrared light . As an infrared sensor, PbS directly detects light, as opposed to thermal detectors, which respond to a change in detector element temperature caused by the radiation. A PbS element can be used to measure radiation in either of two ways: by measuring

1660-464: A waste product. Water heaters can aid the conversion of sulfate in water to hydrogen sulfide gas. This is due to providing a warm environment sustainable for sulfur bacteria and maintaining the reaction which interacts between sulfate in the water and the water heater anode, which is usually made from magnesium metal. H 2 S in the body acts as a gaseous signaling molecule with implications for health and in diseases. Hydrogen sulfide

1743-413: Is boron carbide , whose formula of CB n is a variable non-whole number ratio with n ranging from over 4 to more than 6.5. When the chemical compound of the formula consists of simple molecules , chemical formulae often employ ways to suggest the structure of the molecule. These types of formulae are variously known as molecular formulae and condensed formulae . A molecular formula enumerates

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1826-485: Is stinkdamp . Hydrogen sulfide is a highly toxic and flammable gas ( flammable range : 4.3–46%). It can poison several systems in the body, although the nervous system is most affected. The toxicity of H 2 S is comparable with that of carbon monoxide . It binds with iron in the mitochondrial cytochrome enzymes , thus preventing cellular respiration . Its toxic properties were described in detail in 1843 by Justus von Liebig . Even before hydrogen sulfide

1909-420: Is a double bond between the carbon atoms (and thus each carbon only has two hydrogens), therefore the chemical formula may be written: CH 2 CH 2 , and the fact that there is a double bond between the carbons is implicit because carbon has a valence of four. However, a more explicit method is to write H 2 C=CH 2 or less commonly H 2 C::CH 2 . The two lines (or two pairs of dots) indicate that

1992-429: Is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule , using chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and plus (+) and minus (−) signs. These are limited to a single typographic line of symbols, which may include subscripts and superscripts . A chemical formula

2075-433: Is also known to increase the levels of glutathione, which acts to reduce or disrupt ROS levels in cells. The field of H 2 S biology has advanced from environmental toxicology to investigate the roles of endogenously produced H 2 S in physiological conditions and in various pathophysiological states. H 2 S has been implicated in cancer and Down syndrome and vascular disease. It inhibits Complex IV of

2158-506: Is also produced by heating sulfur with solid organic compounds and by reducing sulfurated organic compounds with hydrogen. It can also be produced by mixing ammonium thiocyanate to concentrated sulphuric acid and adding water to it. Hydrogen sulfide can be generated in cells via enzymatic or non-enzymatic pathways. Three enzymes catalyze formation of H 2 S : cystathionine γ-lyase (CSE), cystathionine β-synthetase (CBS), and 3-mercaptopyruvate sulfurtransferase (3-MST). CBS and CSE are

2241-440: Is convenient when writing equations for nuclear reactions , in order to show the balance of charge more clearly. The @ symbol ( at sign ) indicates an atom or molecule trapped inside a cage but not chemically bound to it. For example, a buckminsterfullerene ( C 60 ) with an atom (M) would simply be represented as MC 60 regardless of whether M was inside the fullerene without chemical bonding or outside, bound to one of

2324-423: Is generally criticised among collectors. Hydrogen sulfide is most commonly obtained by its separation from sour gas , which is natural gas with a high content of H 2 S . It can also be produced by treating hydrogen with molten elemental sulfur at about 450 °C. Hydrocarbons can serve as a source of hydrogen in this process. The very favorable thermodynamics for the hydrogenation of sulfur implies that

2407-420: Is harmless. Hence, low levels of hydrogen sulfide may be tolerated indefinitely. Exposure to lower concentrations can result in eye irritation, a sore throat and cough , nausea, shortness of breath, and fluid in the lungs . These effects are believed to be due to hydrogen sulfide combining with alkali present in moist surface tissues to form sodium sulfide , a caustic . These symptoms usually subside in

2490-409: Is involved in vasodilation in animals, as well as in increasing seed germination and stress responses in plants. Hydrogen sulfide signaling is moderated by reactive oxygen species (ROS) and reactive nitrogen species (RNS). H 2 S has been shown to interact with NO resulting in several different cellular effects, as well as the formation of another signal called nitrosothiol. Hydrogen sulfide

2573-511: Is not a chemical name since it does not contain any words. Although a chemical formula may imply certain simple chemical structures , it is not the same as a full chemical structural formula . Chemical formulae can fully specify the structure of only the simplest of molecules and chemical substances , and are generally more limited in power than chemical names and structural formulae. The simplest types of chemical formulae are called empirical formulae , which use letters and numbers indicating

Lead(II) sulfide - Misplaced Pages Continue

2656-563: Is possible to collate chemical formulae into what is known as Hill system order. The Hill system was first published by Edwin A. Hill of the United States Patent and Trademark Office in 1900. It is the most commonly used system in chemical databases and printed indexes to sort lists of compounds. A list of formulae in Hill system order is arranged alphabetically, as above, with single-letter elements coming before two-letter symbols when

2739-453: Is probably one of the less toxic forms of lead. A large safety risk occurs in the synthesis of PbS using lead carboxylates, as they are particularly soluble and can cause negative physiological conditions. Hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula H 2 S . It is a colorless chalcogen-hydride gas , and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having

2822-535: Is produced when the silver on the surface of the coin reacts with atmospheric hydrogen sulfide. Coins that have been subject to toning by hydrogen sulfide and other sulfur-containing compounds may have the toning add to the numismatic value of a coin based on aesthetics, as the toning may produce thin-film interference , resulting in the coin taking on an attractive coloration. Coins can also be intentionally treated with hydrogen sulfide to induce toning, though artificial toning can be distinguished from natural toning, and

2905-495: Is slightly denser than air. A mixture of H 2 S and air can be explosive. In general, hydrogen sulfide acts as a reducing agent , as indicated by its ability to reduce sulfur dioxide in the Claus process . Hydrogen sulfide burns in oxygen with a blue flame to form sulfur dioxide ( SO 2 ) and water : If an excess of oxygen is present, sulfur trioxide ( SO 3 ) is formed, which quickly hydrates to sulfuric acid : It

2988-459: Is slightly soluble in water and acts as a weak acid ( p K a  = 6.9 in 0.01–0.1 mol/litre solutions at 18 °C), giving the hydrosulfide ion HS . Hydrogen sulfide and its solutions are colorless. When exposed to air, it slowly oxidizes to form elemental sulfur, which is not soluble in water. The sulfide anion S is not formed in aqueous solution. At pressures above 90 GPa ( gigapascal ), hydrogen sulfide becomes

3071-417: Is the case, it would be the first time the substance was identified on a foreign planet. Other less likely candidates for Venus' "snow" are bismuth sulfide and tellurium . Lead(II) sulfide is so insoluble that it is almost nontoxic, but pyrolysis of the material, as in smelting, gives dangerous toxic fumes of lead and oxides of sulfur. Lead sulfide is insoluble and a stable compound in the pH of blood and so

3154-454: Is the condensed molecular/chemical formula for ethanol , which is CH 3 −CH 2 −OH or CH 3 CH 2 OH . However, even a condensed chemical formula is necessarily limited in its ability to show complex bonding relationships between atoms, especially atoms that have bonds to four or more different substituents . Since a chemical formula must be expressed as a single line of chemical element symbols , it often cannot be as informative as

3237-522: Is typically removed by amine gas treating technologies. In such processes, the hydrogen sulfide is first converted to an ammonium salt, whereas the natural gas is unaffected. The bisulfide anion is subsequently regenerated by heating of the amine sulfide solution. Hydrogen sulfide generated in this process is typically converted to elemental sulfur using the Claus Process . The underground mine gas term for foul-smelling hydrogen sulfide-rich gas mixtures

3320-405: Is used to detect hydrogen sulfide because it readily converts to lead(II) sulfide , which is black. Treating metal sulfides with strong acid or electrolysis often liberates hydrogen sulfide. Hydrogen sulfide is also responsible for tarnishing on various metals including copper and silver ; the chemical responsible for black toning found on silver coins is silver sulfide ( Ag 2 S ), which

3403-641: The Bakken formation crude, possibly due to oil field practices, and presented challenges such as "health and environmental risks, corrosion of wellbore, added expense with regard to materials handling and pipeline equipment, and additional refinement requirements". Besides living near gas and oil drilling operations, ordinary citizens can be exposed to hydrogen sulfide by being near waste water treatment facilities, landfills and farms with manure storage. Exposure occurs through breathing contaminated air or drinking contaminated water. In municipal waste landfill sites ,

Lead(II) sulfide - Misplaced Pages Continue

3486-488: The human body produces small amounts of this sulfide and its mineral salts, and uses it as a signalling molecule . Hydrogen sulfide is often produced from the microbial breakdown of organic matter in the absence of oxygen, such as in swamps and sewers; this process is commonly known as anaerobic digestion , which is done by sulfate-reducing microorganisms . It also occurs in volcanic gases , natural gas deposits, and sometimes in well-drawn water. Hydrogen sulfide

3569-663: The spectrum , the so-called short-wavelength infrared (SWIR). Only very hot objects emit radiation in these wavelengths. Cooling the PbS elements, for example using liquid nitrogen or a Peltier element system, shifts its sensitivity range to between approximately 2 and 4 μm . Objects that emit radiation in these wavelengths still have to be quite hot—several hundred degrees Celsius —but not as hot as those detectable by uncooled sensors. (Other compounds used for this purpose include indium antimonide (InSb) and mercury-cadmium telluride (HgCdTe), which have somewhat better properties for detecting

3652-523: The sulfate [SO 4 ] ion. Each polyatomic ion in a compound is written individually in order to illustrate the separate groupings. For example, the compound dichlorine hexoxide has an empirical formula ClO 3 , and molecular formula Cl 2 O 6 , but in liquid or solid forms, this compound is more correctly shown by an ionic condensed formula [ClO 2 ] [ClO 4 ] , which illustrates that this compound consists of [ClO 2 ] ions and [ClO 4 ] ions. In such cases,

3735-486: The 1:1 ratio of component elements. Formaldehyde and acetic acid have the same empirical formula, CH 2 O . This is also the molecular formula for formaldehyde, but acetic acid has double the number of atoms. Like the other formula types detailed below, an empirical formula shows the number of elements in a molecule, and determines whether it is a binary compound , ternary compound , quaternary compound , or has even more elements. Molecular formulae simply indicate

3818-510: The Kraft process), tanneries and sewerage . H 2 S arises from virtually anywhere where elemental sulfur comes in contact with organic material, especially at high temperatures. Depending on environmental conditions, it is responsible for deterioration of material through the action of some sulfur oxidizing microorganisms. It is called biogenic sulfide corrosion . In 2011 it was reported that increased concentrations of H 2 S were observed in

3901-468: The available resources used above in simple condensed formulae. See IUPAC nomenclature of organic chemistry and IUPAC nomenclature of inorganic chemistry 2005 for examples. In addition, linear naming systems such as International Chemical Identifier (InChI) allow a computer to construct a structural formula, and simplified molecular-input line-entry system (SMILES) allows a more human-readable ASCII input. However, all these nomenclature systems go beyond

3984-540: The burial of organic material rapidly leads to the production of anaerobic digestion within the waste mass and, with the humid atmosphere and relatively high temperature that accompanies biodegradation , biogas is produced as soon as the air within the waste mass has been reduced. If there is a source of sulfate bearing material, such as plasterboard or natural gypsum (calcium sulfate dihydrate), under anaerobic conditions sulfate reducing bacteria converts this to hydrogen sulfide. These bacteria cannot survive in air but

4067-468: The carbon atoms. Using the @ symbol, this would be denoted M@C 60 if M was inside the carbon network. A non-fullerene example is [As@Ni 12 As 20 ] , an ion in which one arsenic (As) atom is trapped in a cage formed by the other 32 atoms. This notation was proposed in 1991 with the discovery of fullerene cages ( endohedral fullerenes ), which can trap atoms such as La to form, for example, La@C 60 or La@C 82 . The choice of

4150-399: The charge on a particular atom may be denoted with a right-hand superscript. For example, Na , or Cu . The total charge on a charged molecule or a polyatomic ion may also be shown in this way, such as for hydronium , H 3 O , or sulfate , SO 2− 4 . Here + and − are used in place of +1 and −1, respectively. For more complex ions, brackets [ ] are often used to enclose

4233-480: The chemical formula CH 3 CH=CHCH 3 does not identify. The relative position of the two methyl groups must be indicated by additional notation denoting whether the methyl groups are on the same side of the double bond ( cis or Z ) or on the opposite sides from each other ( trans or E ). As noted above, in order to represent the full structural formulae of many complex organic and inorganic compounds, chemical nomenclature may be needed which goes well beyond

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4316-455: The condensed formula only need be complex enough to show at least one of each ionic species. Chemical formulae as described here are distinct from the far more complex chemical systematic names that are used in various systems of chemical nomenclature . For example, one systematic name for glucose is (2 R ,3 S ,4 R ,5 R )-2,3,4,5,6-pentahydroxyhexanal. This name, interpreted by the rules behind it, fully specifies glucose's structural formula, but

4399-590: The corresponding metal sulfides. Oxidic ores are sometimes treated with hydrogen sulfide to give the corresponding metal sulfides which are more readily purified by flotation . Metal parts are sometimes passivated with hydrogen sulfide. Catalysts used in hydrodesulfurization are routinely activated with hydrogen sulfide. Hydrogen sulfide was a reagent in the qualitative inorganic analysis of metal ions. In these analyses, heavy metal (and nonmetal ) ions (e.g., Pb(II), Cu(II), Hg(II), As(III)) are precipitated from solution upon exposure to H 2 S . The components of

4482-519: The cysteine catabolic pathway. Dietary amino acids, such as methionine and cysteine serve as the primary substrates for the transulfuration pathways and in the production of hydrogen sulfide. Hydrogen sulfide can also be derived from proteins such as ferredoxins and Rieske proteins . Sulfate-reducing (resp. sulfur-reducing ) bacteria generate usable energy under low-oxygen conditions by using sulfates (resp. elemental sulfur) to oxidize organic compounds or hydrogen; this produces hydrogen sulfide as

4565-462: The dehydrogenation (or cracking ) of hydrogen sulfide would require very high temperatures. A standard lab preparation is to treat ferrous sulfide with a strong acid in a Kipp generator : For use in qualitative inorganic analysis , thioacetamide is used to generate H 2 S : Many metal and nonmetal sulfides, e.g. aluminium sulfide , phosphorus pentasulfide , silicon disulfide liberate hydrogen sulfide upon exposure to water: This gas

4648-551: The dissolving of ionic compounds into solution. While, as noted, chemical formulae do not have the full power of structural formulae to show chemical relationships between atoms, they are sufficient to keep track of numbers of atoms and numbers of electrical charges in chemical reactions, thus balancing chemical equations so that these equations can be used in chemical problems involving conservation of atoms, and conservation of electric charge. A chemical formula identifies each constituent element by its chemical symbol and indicates

4731-583: The earliest materials to be used as a semiconductor. Lead sulfide crystallizes in the sodium chloride motif, unlike many other IV-VI semiconductors . Since PbS is the main ore of lead, much effort has focused on its conversion. A major process involves smelting of PbS followed by reduction of the resulting oxide . Idealized equations for these two steps are: The sulfur dioxide is converted to sulfuric acid . Lead sulfide-containing nanoparticle and quantum dots have been well studied. Traditionally, such materials are produced by combining lead salts with

4814-457: The entire formula of the ion with charge +3. This is strictly optional; a chemical formula is valid with or without ionization information, and Hexamminecobalt(III) chloride may be written as [Co(NH 3 ) 6 ] Cl − 3 or [Co(NH 3 ) 6 ]Cl 3 . Brackets, like parentheses, behave in chemistry as they do in mathematics, grouping terms together – they are not specifically employed only for ionization states. In

4897-402: The formula C n H 2 n + 1 OH ( n ≥ 1), giving the homologs methanol , ethanol , propanol for 1 ≤ n ≤ 3. The Hill system (or Hill notation) is a system of writing empirical chemical formulae, molecular chemical formulae and components of a condensed formula such that the number of carbon atoms in a molecule is indicated first, the number of hydrogen atoms next, and then

4980-490: The ionic formula, as in [B 12 H 12 ] , which is found in compounds such as caesium dodecaborate , Cs 2 [B 12 H 12 ] . Parentheses ( ) can be nested inside brackets to indicate a repeating unit, as in Hexamminecobalt(III) chloride , [Co(NH 3 ) 6 ] Cl − 3 . Here, (NH 3 ) 6 indicates that the ion contains six ammine groups ( NH 3 ) bonded to cobalt , and [ ] encloses

5063-409: The largest industrial source of H 2 S is petroleum refineries : The hydrodesulfurization process liberates sulfur from petroleum by the action of hydrogen. The resulting H 2 S is converted to elemental sulfur by partial combustion via the Claus process , which is a major source of elemental sulfur. Other anthropogenic sources of hydrogen sulfide include coke ovens, paper mills (using

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5146-477: The latter case here, the parentheses indicate 6 groups all of the same shape, bonded to another group of size 1 (the cobalt atom), and then the entire bundle, as a group, is bonded to 3 chlorine atoms. In the former case, it is clearer that the bond connecting the chlorines is ionic , rather than covalent . Although isotopes are more relevant to nuclear chemistry or stable isotope chemistry than to conventional chemistry, different isotopes may be indicated with

5229-427: The longer IR wavelengths.) The high dielectric constant of PbS leads to relatively slow detectors (compared to silicon , germanium , InSb, or HgCdTe). Elevations above 2.6 km (1.63 mi) on the planet Venus are coated with a shiny substance. Though the composition of this coat is not entirely certain, one theory is that Venus " snows " crystallized lead sulfide much as Earth snows frozen water. If this

5312-420: The main proponents of H 2 S biogenesis, which follows the trans-sulfuration pathway. These enzymes have been identified in a breadth of biological cells and tissues, and their activity is induced by a number of disease states. These enzymes are characterized by the transfer of a sulfur atom from methionine to serine to form a cysteine molecule. 3-MST also contributes to hydrogen sulfide production by way of

5395-579: The mitochondrial electron transport chain, which effectively reduces ATP generation and biochemical activity within cells. Hydrogen sulfide is mainly consumed as a precursor to elemental sulfur. This conversion, called the Claus process , involves partial oxidation to sulfur dioxide. The latter reacts with hydrogen sulfide to give elemental sulfur. The conversion is catalyzed by alumina. Many fundamental organosulfur compounds are produced using hydrogen sulfide. These include methanethiol , ethanethiol , and thioglycolic acid . Hydrosulfides can be used in

5478-474: The moist, warm, anaerobic conditions of buried waste that contains a high source of carbon – in inert landfills, paper and glue used in the fabrication of products such as plasterboard can provide a rich source of carbon – is an excellent environment for the formation of hydrogen sulfide. In industrial anaerobic digestion processes, such as waste water treatment or the digestion of organic waste from agriculture , hydrogen sulfide can be formed from

5561-405: The name is not a chemical formula as usually understood, and uses terms and words not used in chemical formulae. Such names, unlike basic formulae, may be able to represent full structural formulae without graphs. In chemistry , the empirical formula of a chemical is a simple expression of the relative number of each type of atom or ratio of the elements in the compound. Empirical formulae are

5644-531: The number of all other chemical elements subsequently, in alphabetical order of the chemical symbols . When the formula contains no carbon, all the elements, including hydrogen, are listed alphabetically. By sorting formulae according to the number of atoms of each element present in the formula according to these rules, with differences in earlier elements or numbers being treated as more significant than differences in any later element or number—like sorting text strings into lexicographical order —it

5727-433: The number of atoms to reflect those in the molecule, so that the molecular formula for glucose is C 6 H 12 O 6 rather than the glucose empirical formula, which is CH 2 O . However, except for very simple substances, molecular chemical formulae lack needed structural information, and are ambiguous. For simple molecules, a condensed (or semi-structural) formula is a type of chemical formula that may fully imply

5810-494: The numbers of each type of atom in a molecule of a molecular substance. They are the same as empirical formulae for molecules that only have one atom of a particular type, but otherwise may have larger numbers. An example of the difference is the empirical formula for glucose, which is CH 2 O ( ratio 1:2:1), while its molecular formula is C 6 H 12 O 6 ( number of atoms 6:12:6). For water, both formulae are H 2 O . A molecular formula provides more information about

5893-409: The numerical proportions of atoms of each type. Molecular formulae indicate the simple numbers of each type of atom in a molecule, with no information on structure. For example, the empirical formula for glucose is CH 2 O (twice as many hydrogen atoms as carbon and oxygen ), while its molecular formula is C 6 H 12 O 6 (12 hydrogen atoms, six carbon and oxygen atoms). Sometimes

5976-476: The production of thiophenol . Upon combining with alkali metal bases, hydrogen sulfide converts to alkali hydrosulfides such as sodium hydrosulfide and sodium sulfide : Sodium sulfides are used in the paper making industry. Specifically, salts of SH break bonds between lignin and cellulose components of pulp in the Kraft process . As indicated above, many metal ions react with hydrogen sulfide to give

6059-603: The proportionate number of atoms of each element. In empirical formulae, these proportions begin with a key element and then assign numbers of atoms of the other elements in the compound, by ratios to the key element. For molecular compounds, these ratio numbers can all be expressed as whole numbers. For example, the empirical formula of ethanol may be written C 2 H 6 O because the molecules of ethanol all contain two carbon atoms, six hydrogen atoms, and one oxygen atom. Some types of ionic compounds, however, cannot be written with entirely whole-number empirical formulae. An example

6142-435: The reduction of sulfate and the degradation of amino acids and proteins within organic compounds. Sulfates are relatively non-inhibitory to methane forming bacteria but can be reduced to H 2 S by sulfate reducing bacteria , of which there are several genera. A number of processes have been designed to remove hydrogen sulfide from drinking water . Hydrogen sulfide is commonly found in raw natural gas and biogas. It

6225-724: The resulting solid are then identified by their reactivity. Hydrogen sulfide is used to separate deuterium oxide, or heavy water , from normal water via the Girdler sulfide process . A suspended animation-like state has been induced in rodents with the use of hydrogen sulfide, resulting in hypothermia with a concomitant reduction in metabolic rate. Oxygen demand was also reduced, thereby protecting against hypoxia . In addition, hydrogen sulfide has been shown to reduce inflammation in various situations. Volcanoes and some hot springs (as well as cold springs ) emit some H 2 S . Hydrogen sulfide can be present naturally in well water, often as

6308-463: The same molecular formula C 4 H 10 , but they have different structural formulas as shown. The connectivity of a molecule often has a strong influence on its physical and chemical properties and behavior. Two molecules composed of the same numbers of the same types of atoms (i.e. a pair of isomers ) might have completely different chemical and/or physical properties if the atoms are connected differently or in different positions. In such cases,

6391-638: The sense of smell, creating temporary anosmia , so victims may be unaware of its presence until it is too late. Safe handling procedures are provided by its safety data sheet (SDS) . Since hydrogen sulfide occurs naturally in the body, the environment, and the gut, enzymes exist to metabolize it. At some threshold level, believed to average around 300–350 ppm, the oxidative enzymes become overwhelmed. Many personal safety gas detectors, such as those used by utility, sewage and petrochemical workers, are set to alarm at as low as 5 to 10 ppm and to go into high alarm at 15 ppm. Metabolism causes oxidation to sulfate, which

6474-426: The standard for ionic compounds , such as CaCl 2 , and for macromolecules, such as SiO 2 . An empirical formula makes no reference to isomerism , structure, or absolute number of atoms. The term empirical refers to the process of elemental analysis , a technique of analytical chemistry used to determine the relative percent composition of a pure chemical substance by element. For example, hexane has

6557-498: The standards of chemical formulae, and technically are chemical naming systems, not formula systems. For polymers in condensed chemical formulae, parentheses are placed around the repeating unit. For example, a hydrocarbon molecule that is described as CH 3 (CH 2 ) 50 CH 3 , is a molecule with fifty repeating units. If the number of repeating units is unknown or variable, the letter n may be used to indicate this formula: CH 3 (CH 2 ) n CH 3 . For ions ,

6640-523: The symbol has been explained by the authors as being concise, readily printed and transmitted electronically (the at sign is included in ASCII , which most modern character encoding schemes are based on), and the visual aspects suggesting the structure of an endohedral fullerene. Chemical formulae most often use integers for each element. However, there is a class of compounds, called non-stoichiometric compounds , that cannot be represented by small integers. Such

6723-418: The tiny photocurrent the photons cause when they hit the PbS material, or by measuring the change in the material's electrical resistance that the photons cause. Measuring the resistance change is the more commonly used method. At room temperature , PbS is sensitive to radiation at wavelengths between approximately 1 and 2.5 μm . This range corresponds to the shorter wavelengths in the infra-red portion of

6806-462: Was discovered, Italian physician Bernardino Ramazzini hypothesized in his 1713 book De Morbis Artificum Diatriba that occupational diseases of sewer-workers and blackening of coins in their clothes may be caused by an unknown invisible volatile acid (moreover, in late 18th century toxic gas emanation from Paris sewers became a problem for the citizens and authorities). Although very pungent at first (it smells like rotten eggs ), it quickly deadens

6889-473: Was used by the British Army as a chemical weapon during World War I . It was not considered to be an ideal war gas, partially due to its flammability and because the distinctive smell could be detected from even a small leak, alerting the enemy to the presence of the gas. It was nevertheless used on two occasions in 1916 when other gases were in short supply. Chemical formula A chemical formula

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