The mouthpiece of the gaming generation, The Escapist aims to capture and celebrate the contemporary video gaming lifestyle and the diverse global video game culture by way of in-depth features, thought provoking articles and.The materials used in sculpture are diverse, changing throughout history. The classic materials, with outstanding durability, are metal, especially bronze, stone and pottery, with wood, bone and antler less durable but cheaper. Collectibles come in all shapes and sizes and all price points. ThinkGeek has the top selection to complement your collection. For key points in Batman's history see Batman's career timeline. Batman's history has undergone various revisions, both minor and major. Few elements of the character's history have remained constant. Sildenafil Citrate 25/50/100/120/150/200mg. Generic Viagra is used to treat male Impotence also known as Erectile Dysfunction. Also, it has been approved by US FDA for treating pulmonary arterial hypertension. Sulfur - Wikipedia, the free encyclopedia. Sulfur, 1. 6SGeneral properties. Name, symbolsulfur, SPronunciation. SUL- f. It is an abundant, multivalentnon- metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow crystalline solid at room temperature. Chemically, sulfur reacts with all elements except for gold, platinum, iridium, nitrogen, tellurium, iodine and the noble gases. Elemental sulfur occurs naturally as the element (native sulfur), but most commonly occurs in combined forms as sulfide and sulfate minerals. Being abundant in native form, sulfur was known in ancient times, being mentioned for its uses in ancient India, ancient Greece, China, and Egypt. In the Bible, sulfur is called brimstone. The greatest commercial use of the element is the production of sulfuric acid for sulfate and phosphate fertilizers, and other chemical processes. The element sulfur is used in matches, insecticides, and fungicides. Many sulfur compounds are odoriferous, and the smells of odorized natural gas, skunk scent, grapefruit, and garlic are due to organosulfur compounds. Hydrogen sulfide gives the characteristic odor to rotting eggs and other biological processes. Sulfur is an essential element for all life, but almost always in the form of organosulfur compounds or metal sulfides. Three amino acids (cysteine, cystine, and methionine) and two vitamins (biotin and thiamine) are organosulfur compounds. Many cofactors also contain sulfur including glutathione and thioredoxin and iron. Elemental sulfur is not common in higher forms of life, but is both a product and an oxidant for various bacteria. Spelling and etymology. The spelling sulfur appears toward the end of the Classical period. The parallel f~ph spellings continued in Britain until the 1. The IUPAC adopted the spelling sulfur in 1. Nomenclature Committee of the Royal Society of Chemistry in 1. Britain. The Spanish and Portuguese words are prefixed with the Arabic article, despite not being Arabic words. The point group of cyclo- S8 is D4d and its dipole moment is 0 D. Between its melting and boiling temperatures, octasulfur changes its allotrope again, turning from . Molten sulfur assumes a dark red color above 2. The density of sulfur is about 2 g. Sulfur is insoluble in water but soluble in carbon disulfide and, to a lesser extent, in other nonpolar organic solvents, such as benzene and toluene. The first and second ionization energies of sulfur are 9. J. Despite such figures, the +2 oxidation state is rare, with +4 and +6 being more common. The fourth and sixth ionization energies are 4. J. Some of those reactions need elevated temperatures. X- ray crystallography studies show that the amorphous form may have a helical structure with eight atoms per turn. The long coiled polymeric molecules make the brownish substance elastic, and in bulk this form has the feel of crude rubber. This form is metastable at room temperature and gradually reverts to crystalline molecular allotrope, which is no longer elastic. This process happens within a matter of hours to days, but can be rapidly catalyzed. Isotopes. The differences between minerals can be used to estimate the temperature of equilibration. Sulfur with a distinctive isotopic composition has been used to identify pollution sources, and enriched sulfur has been added as a tracer in hydrologic studies. Differences in the natural abundances can be used in systems where there is sufficient variation in the 3. S of ecosystem components. Rocky Mountain lakes thought to be dominated by atmospheric sources of sulfate have been found to have different . Ordinary chondrites contain on average 2. It is normally present as troilite (Fe. S), but there are exceptions, with carbonaceous chondrites containing free sulfur, sulfates and other sulfur compounds. Such deposits are polycrystalline, with the largest documented single crystal measuring 2. Native sulfur may be produced by geological processes alone. Fossil- based sulfur deposits from salt domes were until recently the basis for commercial production in the United States, Russia, Turkmenistan, and Ukraine. Such sources are now of secondary commercial importance, and most are no longer worked. Common naturally occurring sulfur compounds include the sulfide minerals, such as pyrite (iron sulfide), cinnabar (mercury sulfide), galena (lead sulfide), sphalerite (zinc sulfide) and stibnite (antimony sulfide); and the sulfates, such as gypsum (calcium sulfate), alunite (potassium aluminium sulfate), and barite (barium sulfate). On Earth, just as upon Jupiter's moon Io, elemental sulfur occurs naturally in volcanic emissions, including emissions from hydrothermal vents. Production. 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. Today's sulfur production is as a side product of other industrial processes such as oil refining; in these processes, sulfur often occurs as undesired or detrimental compounds that are extracted and converted to elemental sulfur. As a mineral, native sulfur under salt domes is thought to be a fossil mineral resource, produced by the action of ancient bacteria on sulfate deposits. It was removed from such salt- dome mines mainly by the Frasch process. Throughout the 2. 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 2. Organosulfur compounds, undesirable impurities in petroleum, may be upgraded by subjecting them to hydrodesulfurization, which cleaves the C. This process entails oxidation of some hydrogen sulfide to sulfur dioxide and then the comproportionation of the two. Countries producing more than 5 Mt are China (9. US (8. 8), Canada (7. Russia (7. 1). Sulfur forms stable compounds with all elements except the noble gases. Sulfur polycations. Bucholz, but the cause of the color and the structure of the polycations involved was only determined in the late 1. S8. 2+ is deep blue, S4. S1. 62+ is red. When dissolved in water, hydrogen sulfide is mildly acidic. Protonation of these polysulfide anions produces the polysulfanes, H2. Sx where x = 2, 3, and 4. Zig- zag (b) and straight (c) S chains inside double- wall CNTs. Sulfur dioxide and sulfites (SO2. Sulfur trioxide and sulfates (SO2. Sulfuric acid and SO3 combine to give oleum, a solution of pyrosulfuric acid (H2. S2. O7) in sulfuric acid. Thiosulfate salts (S2. O2. Sodium dithionite (Na. S2. O4), contains the more highly reducing dithionite anion (S2. O2. 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 rarely used organic reagent that and is highly toxic. Sulfuryl chloride and chlorosulfuric acid are derivatives of sulfuric acid; thionyl chloride (SOCl. 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. Oxidation of thiocyanate gives thiocyanogen, (SCN)2 with the connectivity NCS- SCN. Phosphorus sulfides are numerous, the most important commercially being the cages P4. S1. 0 and P4. S3. 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 (Pb. S) 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 . Sulfur corrodes many metals through tarnishing. Organic compounds. 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. 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. In the most common type of industrial . This process, patented in 1. Because of the heat and sulfur, the process was named vulcanization, after the Roman god of the forge and volcanism. History. English translations of the Bible commonly referred to burning sulfur as . It is from this part of the Bible that Hell is implied to . 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. He mentions its use for fumigation, medicine, and bleaching cloth. It remains an ingredient of black gunpowder. Indian alchemists, practitioners of . 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. By the late 1. 8th century, about 2,0. Marseilles, France for the production of sulfuric acid by the Leblanc process. In industrializing Britain, with the repeal of tariffs on salt in 1. Sicily surged upward.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. Archives
December 2016
Categories |