Sulfur reduced inorganic

In summary, the capacity to synthesize both hemoproteins and iron sulfur proteins appears to be a ubiquitous attribute in organisms attacking reduced inorganic substrates. If the reactions by which these cells obtain energy represent relics of ancient forms of metabolism, it can only be concluded that heme formation and iron-sulfur coordination must have been invented at a very early stage in evolution. 

The biotransformations of sulfur compounds by microorganisms can have large-scale impacts on global chemistry. As an example, sulfate-reducing bacteria have, throughout histoiy, formed major deposits of elemental sulfur and iron sulfides on Earth, and these processes are continuing today (1). Contemporary sulfate-reduction coupled with the oxidation of reduced inorganic sulfur... 

Wilkin, R.T. and K.J. Bischoff. 2006. Coulometric determination of total sulfur and reduced inorganic sulfur fractions in environmental samples. Talanta 70 766-773. 

The average concentrations of reduced inorganic sulfur species in the anoxic zone of the Black Sea measured using a new colorimetric method developed by Volkov [61,62] are summarized in Table 3. Presented elemental sulfur data refer to the stun of elemental sulfur allotropes (zero-valent sulfur) and the zero-valent sulfur derived from some fraction (n - 1) of the original polysulfide S 2. Thiosulfate data in the table represent the total amount of thiosulfate, sulfite, and polythionates. At some stations in the Black Sea, Volkov [61] observed a concentration maximum of elemental sulfur at the oxic/anoxic interface associated with sulfide oxidation by dissolved oxygen and/or Mn oxyhydroxides. Increasing with depth, elemental sulfur concentrations are probably explained by the ongoing process of polysulfide formation... 

Thiobacillus ferrooxidans is an obligate chemoautotrophic and acidophilic organism and is able to oxidize Fe2+, S°, metal sulfides, and other reduced inorganic sulfur compounds. Thiobacillus thiooxidans has also been isolated from acid mine wastes and has been determined that can oxidize both elemental sulfur and sulfide to sulfuric acid (S° + 1.502 + H20 - H2S04 and S2 + 202 + 2H+ - H2S04) (Brierley, 1982 Lundgren and Silver, 1980). However, T. thiooxidans cannot oxidize Fe2+ (Harrison, 1984). 

Aspiras, R. B., D. R. Keeney, and G. Chesters. 1972. Determination of reduced inorganic sulfur forms as suphide by zinc-hydrochloric acid distillation. Anal. Lett. 5 425-432. 

Canfield, D.E., Raiswell, R., Westrich, J.T., Reaves, C.M. Berner, R.A. (1986) The use of chromium reduction in the analysis of reduced inorganic sulfur in sediments and shales. Chemical Geology 16, 59-62. 

Giblin, A. E., Hole, W., Likens, G. N., Howarth, R. W. (1992). The importance of reduce inorganic sulfur to the sulfur cycle of lakes. In Interactions of Biogeochemical Cycles in Aquatic Systems, Part 7. SCOPE/UNEP Sonderband, Hamburg, 233-244. 

Chromium reduction to measure reduced inorganic sulfur compounds in sediments was proposed by Zhabina and Volkov (1978). Since then it has found wide use internationally (Sullivan etal. 1999), particularly when pyritic sediments and acid volatile mono-sulfides are expected. The method is not measurably affected by sulfur in organic matter or sulfates (Canfield etal. 1986 Morse Cornwell 1987). Accordingly, this chromium reducible sulfur method (SCr) is especially useful on samples with appreciable organic matter and also for sandy soils where the %S action criterion is very low (e.g. as low as 0.03%S). 

This method by Sullivan etal. (2000) is based on the conversion of reduced inorganic sulfur to H2S by hot acidic chromium(II) chloride (CrCl2) solution. The hydrogen sulfide (H2S) evolved is trapped in a zinc acetate solution as ZnS, and subsequently quantified by iodometric titration (see Fig. 5.1). The reduced inorganic sulfur compounds measured are (i) pyrite and other iron disulfides (ii) elemental sulfur and (iii) acid volatile sulfides (e.g. greigite and mackinawite). The method can be made specific to the iron disulfide fractions if pre-treatments are used to remove the acid volatile sulfides and elemental S fractions. 

Stumm, W. Morgan, J.J. (1996) Aquatic Chemistry. 3rd Edn. Wiley-Interscience, New York, NY. Sullivan, L.A., Bush, R.T. McConchie, D.M. (2000) A modified chromium-reducible sulfur method for reducing inorganic sulfur optimum reaction time for acid sulfate soil. Aust. J. Soil Res., 38,... 

In conjunction with XANES and X-ray diffraction, initial investigations involving synchrotron based X-ray microspectrometry (at ESRF) has revealed two types of reduced sulfur compounds in the timbers of the Mary Rose. Organosulfur compounds are found in the lignin-rich middle lamella between wood cell walls, mostly as thiols, disulfides and elemental sulfur, while inorganic iron sulfides including iron pyrite, occurs in separate particles in the cell lumen. 

Reduced inorganic sulfur (elemental sulfur and sulfide)... 

Sulfate reduction accounts for a portion of the total respiration in salt marshes and, when the reduced, inorganic sulfur in oxidized energy is released and exported from the system. Wetlands also emits reduced sulfur gases to the atmosphere. DMS is the dominant form emitted from salt marshes. 

Howarth, R. W. and J. M. Teal. 1980. Energy flow in a salt marsh ecosystem the role of reduced inorganic sulfur compounds. Am. Nat. 116 862-872. 

Hsieh, Y. R Yang, C. H. (1989) Diffusion methods for the determination of reduced inorganic sulfur species in sediments. Limnology Oceanography 34, 1126-1130. 

Chemoautotrophs These use electrons from reduced inorganic compounds as their energy source and carbon dioxide as their source of carbon. Inorganic compounds can include hydrogai sulfide (H2S), elemental sulfur (S), ammonia (NHj), nitrite ions (NO2), hydrogen (H), and ferrous ions (Fe ). 

Another important example of a redox titration for inorganic analytes, which is important in industrial labs, is the determination of water in nonaqueous solvents. The titrant for this analysis is known as the Karl Fischer reagent and consists of a mixture of iodine, sulfur dioxide, pyridine, and methanol. The concentration of pyridine is sufficiently large so that b and SO2 are complexed with the pyridine (py) as py b and py SO2. When added to a sample containing water, b is reduced to U, and SO2 is oxidized to SO3. 

Titanium whites resist various atmospheric contaminants such as sulfur dioxide, carbon dioxide, and hydrogen sulfide. Under normal conditions they are not readily reduced, oxidi2ed, or attacked by weak inorganic and organic acids. Titanium dioxide dissolves slightly in bases, hydrofluoric acid, and hot sulfuric acid. Owing to its chemical inertness, titanium dioxide is a nontoxic, environmentally preferred white pigment. 

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