Thiosulfates and tetrathionates

In the first phase, in the presence of an excess of bisulfite, thiosulfate, and tetrathionate are formed by the overall reactions ... 

Thiosulfate and tetrathionate ions are colorless. The half-equilibrium S40e /S203 obeys the equation... 

The quantitative conversion of thiosulfate to tetrathionate is unique with iodine. Other oxidant agents tend to carry the oxidation further to sulfate ion or to a mixture of tetrathionate and sulfate ions. Thiosulfate titration of iodine is best performed in neutral or slightly acidic solutions. If strongly acidic solutions must be titrated, air oxidation of the excess of iodide must be prevented by blanketing the solution with an inert gas, such as carbon dioxide or... 

Foreign ions are masked with a composite EDTA-sodium hexametaphosphate reagent and interference by sulfide is overcome by the addition of mercuric chloride, which also mitigates interference by thiosulfate, sulfate, tetrathionate and iodide, and the precipitated mercuric sulfide is filtered off prior to the addition of chromogenic reagents and spectrophotometry. Beer s law is obeyed up to levels of 20 p,g nitrite in a 60 ml test solution. 

Zopfi J, Ferdelman TG, Fossing H (2004) Distribution and fate of sulfur intermediates - sulfite, tetrathionate, thiosulfate, and elemental sulfur - in marine sediments. In Amend JP, Edwards KJ, Lyons TW (eds) Sulfur biogeochemistry - past and present. Geological Society of America special paper 379, p 97... 

As shown, thiocyanogen may oxidize iodide to iodine, add to carbon-carbon double bonds, form a tri-pseudohalide (analogous to CsBrs), and oxidize thiosulfate to tetrathionate (as does I2). The chlorination of (SCN)2 is formally similar to the chlorination of I2 to form ICi3. 

Thiosulfate Hydrogen peroxide Sulfate and tetrathionate (pH dependent)... 

Triiodide ion is determined by titration with a sodium thiosulfate (Na2S203) solution. The products are iodide ion and tetrathionate ion (S4062-). 

Moderately thermophilic bacteria, those with an optimum temperature for growth of between 45 and 50°C, have been isolated from a variety of sites, such as mud springs, coal piles, various mineral dumps, and drainage waters from sulfide ore deposits, dumps, and mines (22). Some examples are listed in Table I. Mixed bacterial cultures isolated from such environments have been purified by serial dilution and plating on thiosulfate or tetrathionate agar (83). Some moderate thermophiles are active over a wide temperature range. A mixed culture oxidized pyrite at 30°C as rapidly as T. ferrooxidans alone and carried out the same reactions at temperatures over 50°C (6). These properties are of considerable value in commercial operations (Section V). 

Figure 12.18 Eh-pH diagram for aqueous species in the system S-02-H20 at 25°C neglecting sulfate, bisulfate, and elemental sulfur showing significant stability fields for sulfite and bisulfite, thiosulfate and its conjugate acid, and tetrathionate. Reprinted from Geochim. et Cosmochim. Acta, 56, M. A. Williamson and J. D. Rimstidt, Correlation between structure and thermodynamic properties of aqueous sulfur species, 3867-80, 1992, with permission from Elsevier Science Ltd., The Boulevard, Langford Lane, Kidlington 0X5 1GB, U.K.

There are many other oxoacids of sulfur, of which the most important are peroxodisulfate j which has a peroxo (O—O) bond, and compounds with S-S bonds including thiosulfate dithionite and tetrathionate. The reaction... 

However, with trithionate at the given conditions, Reaction 31 yields one mole of thiosulfate and three moles of sulfur. In addition the reaction rate increases in the presence of thiosulfate. These suggest that the main course of the reaction with hydrogen sulfide proceeds through the initial formation of tetrathionate ... 

B. Specific drugs and antidotes. Sodium thiosulfate may convert Iodine to Iodide and tetrathionate, but Is not recommended for intravenous use because iodine is rapidly converted to Iodide In the body. 

Elemental sulfur, thiosulfates, metal sulfides, H2S, and tetrathionates can be oxidized to sulfuric acid by microorganisms generically referred to as thiobacilli. Corrosion in sewers and other concrete structures is often due to oxidation of sulfides generated by the activities of SRB and may occur in many steps. Concrete is a moderately porous mixture of alkaline inorganic precipitates and mineral aggregates. Anaerobic conditions in sewage support SRB that convert sulfate to H2S, which volatilizes to the sewer atmosphere and redissolves in condensate on the sewer crown [43] (Fig. 6). A second community of microorganisms at the... 

Williamson and Rimstidt (1993) reported the rate of decomposition of ferric thiosulfate to form ferrous iron and tetrathionate ions. The reaction brings two ferric thiosulfate molecules together into an activated complex, which decomposes to form two ferrous ions and a tetrathionate ion. 

The thiosulfate anion reacts rapidly with molecular iodine, bleaching the brown/purple color of the latter to produce colorless iodide and tetrathionate, 8406 . 

Zopfi, J., T.G. Ferdelman, and H. Fossing, Distribution and Fate of Sulfur Intermediates—Sulfite, Tetrathionate, Thiosulfate, and Elemental Sulfur—in Marine Sediments Geological Society of America Special Paper 379, 2004. 

Gold thiosulfate complexes of the form Na2[Au(S202)2] 2H20 [19153-98-1] are prepared by addition of gold trichloride to concentrated sodium thiosulfate solution (89). The gold is completely reduced and some thiosulfate is oxidized to tetrathionate. This complex has been used in the treatment of rheumatoid arthritis. 

Sodium (and potassium) tetrathionate, M2S4O5, can be made by oxidation of thiosulfate by I2 (p. 714) and the free acid liberated (in aqueous solution) by addition of the stoichiometric amount of tartaric acid. 

Iodine reacts with thiosulfate ion, S 2-, to give iodide ion and the tetrathionate ion, S4062-. 

Although the metabolism of tetrathionate has not been established in detail, it presumably takes place via thiosulfate, sulhte, and sulhde. Tetrathionate, which is a component of some media for enrichment of salmonellas, is able to support the anaerobic growth of Salmonella sp. using glycerol or acetate, and S. enterica with ethanolamine or propan-l,2-diol when vitamin Bj2 is available (Price-Carter et al. 2001). 

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