Sulfur-containing compounds sulfide

An analogous fragmentation process occurs m the mass spectra of sulfides As with other sulfur containing compounds the presence of sulfur can be inferred by a peak at m/z of M-l-2... 

The physical properties of the principal constituents of natural gas are Hsted in Table 5. These gases are odorless, but for safety reasons, natural gas is odorized before distribution to provide a distinct odor to warn users of possible gas leaks in equipment. Sulfur-containing compounds such as organic mercaptans, aUphatic sulfides, and cycHc sulfur compounds are effective odorants at low concentrations and are added to natural gas at levels ranging from 4 to 24mg/m. ... 

The catalysts are prepared by impregnating the support with aqueous salts of molybdenum and the promoter. In acidic solutions, molybdate ions are present largely in the form of heptamers, [Mo2024] , and the resulting surface species are beHeved to be present in islands, perhaps containing only seven Mo ions (100). Before use, the catalyst is treated with H2 and some sulfur-containing compounds, and the surface oxides are converted into the sulfides that are the catalyticaHy active species. 

Thiobacillus thiooxidans is an aerobic organism that oxidizes various sulfur-containing compounds to form sulfuric acid. These bacteria are sometimes found near the tops of tubercles (see Chap. 3, Tubercu-lation ). There is a symbiotic relationship between Thiobacillus and sulfate reducers Thiobacillus oxidizes sulfide to sulfate, whereas the sulfate reducers convert sulfide to sulfate. It is unclear to what extent Thiobacillus directly influences corrosion processes inside tubercles. It is more likely that they indirectly increase corrosion by accelerating sulfate-reducer activity deep in the tubercles. 

Sulfur Compounds. All crude oils contain sulfur in one of several forms including elemental sulfur, hydrogen sulfide, carbonyl sulfide (COS), and in aliphatic and aromatic compounds. The amount of sulfur-containing compounds increases progressively with an increase in the boiling point of the fraction. A majority of these compounds have one sulfur atom per molecule, but certain aromatic and polynuclear aromatic molecules found in low concentrations in crude oil contain two and even three sulfur atoms. Identification of the individual sulfur compounds in the heavy fractions poses a considerable challenge to the analytical chemist. 

Sulfur-containing compounds [1-3] e.g. thiols [4, 5] and thioethers [5] sulfide ions [4] thiourea derivatives... 

Activities of ALA-S and Haem-S were decreased after exposure to hydrogen sulfide. However, the changes in heme metabolism are not specific for hydrogen sulfide, and other sulfur-containing compounds such as methyl mercaptan can produce similar effects. 

The only information that provided an assessment of exposure of children and adolescents to hydrogen sulfide was that developed during the South Karelia Air Pollution Study (Mortilla et al. 1994b) however, these exposures were complicated by simultaneous exposure to other sulfur-containing compounds as well as particulates. Additional exposure information is needed from communities where only hydrogen sulfide exceeds background levels. 

Metal sulfides may be prepared by simply passing a sulfur-containing compound over the metal in a stream of hydrogen. Such catalysts are fairly immune to typical nonmetallic poisons. 

Carbon reacts also with other sulfur-containing compounds with resulting fixation of sulfur. Reaction of various forms of carbon with hydrogen sulfide was reported by Baraniecky, Riley, and Streeter (126) and by Polansky, Knapp, and Kinney (128). The reaction of carbon blacks with hydrogen sulfide and with sulfur was studied extensively by Studebaker (86). At 150°, the increase in sulfur content was proportional to the quinone content as measured by catalytic hydrogenation using Adams catalyst (see page 203). 

Soil In soil and water, chemical and biological mediated reactions can transform ethylene dibromide in the presence of hydrogen sulfides to ethyl mercaptan and other sulfur-containing compounds (Alexander, 1981). 

Divalent sulfur is a poison for most noble metal catalysts so that catalytic hydrogenation of sulfur-containing compounds poses serious problems (p. 10). However, allyl phenyl sulfide was hydrogenated over tris trisphenyl-phosphine)rhodium chloride in benzene to give 93% yield of phenyl propyl sulfide [674. ... 

Note 2 A classic example of vulcanization is the crosslinking of c/s-polyisoprene through sulfide bridges in the thermal treatment of natural rubber with sulfur or a sulfur-containing compound. 

Organisms such as Thiobacillus thiooxidans and Clostridium species have been linked to accelerated corrosion of mild steel. Aerobic Thiobacillus oxidizes various sulfur-containing compounds such as sulfides to sulfates. This process promotes a symbiotic relationship between Thiobacillus and sulfate-reducing bacteria. Also, Thiobacillus produces sulfuric acid as a metabolic by-product of sulfide oxidation. 

Sulfate shows two peaks, one in the coarse particle mode associated with sea salt, and one in the fine particle mode. The smaller peak is expected since the nss-S04 is formed from the oxidation of S02 and other sulfur-containing compounds such as dimethyl sulfide. The small size of particles containing ammonium reflects the uptake of the gaseous base NH3 into the smaller acidic particles. 

Amphipathic substances such as we have discussed throughout this chapter are used as collectors. Alkyl compounds with C8 to C18 chains are widely used with carboxylate, sulfate, or amine polar heads. For sulfide minerals, sulfur-containing compounds such as mercaptans, monothiocarbonates, and dithiophosphates are used as collectors. The most important collectors for sulfides are xanthates, the general formula for which is... 

Some interesting aspects of the mechanism of the selective introduction of fluorine into sulfur-containing compounds arc discussed52 below. A sulfonium ion can be obtained by the oxidation of sulfides. 

There is one report in which sulfides are oxidized by PDC in aqueous acetic acid however normally the oxidation of alcohols is quicker, so that selective oxidation of alcohols with PDC is possible in the presence of sulfur containing compounds, such as thiophenes,153 aryl sulfides,154 alkyl sulfides155 and dithioacetals.156... 

It is of note that alkaline and acid phosphatase exhibit no silikatase activity. Divalent sulfur-containing compounds, such as sulfide, methionine, cysteine and glutathione have a positive effect on silica uptake536) also water temperature and silica concentration in the aqueous phase control the Si-cycle in cellular systems529-531, 53 ). 

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