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Sulfite reductions

Table I also shows the great diversity of organisms in which iron—sulfur proteins have been detected. Thus far there is no organism which when appropriately examined has not contained an iron-sulfur protein, either in the soluble or membrane-bound form. Iron-sulfur proteins catalyze reactions of physiological importance in obligate anaerobic bacteria, such as hydrogen uptake and evolution, ATP formation, pyruvate metabolism, nitrogen fixation, and photosynthetic electron transport. These properties and reactions can be considered primitive and thus make iron-sulfur proteins a good place to start the study of evolution. These key reactions are also important in higher organisms. Other reactions catalyzed by iron-sulfur proteins can be added such as hydroxylation, nitrate and nitrite reduction, sulfite reduction, NADH oxidation, xanthine oxidation, and many other reactions (Table II). Table I also shows the great diversity of organisms in which iron—sulfur proteins have been detected. Thus far there is no organism which when appropriately examined has not contained an iron-sulfur protein, either in the soluble or membrane-bound form. Iron-sulfur proteins catalyze reactions of physiological importance in obligate anaerobic bacteria, such as hydrogen uptake and evolution, ATP formation, pyruvate metabolism, nitrogen fixation, and photosynthetic electron transport. These properties and reactions can be considered primitive and thus make iron-sulfur proteins a good place to start the study of evolution. These key reactions are also important in higher organisms. Other reactions catalyzed by iron-sulfur proteins can be added such as hydroxylation, nitrate and nitrite reduction, sulfite reduction, NADH oxidation, xanthine oxidation, and many other reactions (Table II).
Reduction (sulfite) Reduced viscosity of water dispersion increased viscosity in salt solution and resistance to aggregation ... [Pg.45]

BrOg Reduction with arsenate(III), hydrazine, sulfite, or thiosulfate... [Pg.1177]

Reductions. Hydrazine is a very strong reducing agent. In the presence of oxygen and peroxides, it yields primarily nitrogen and water with more or less ammonia and hydrazoic acid [7782-79-8]. Based on standard electrode potentials, hydrazine in alkaline solution is a stronger reductant than sulfite but weaker than hypophosphite in acid solution, it falls between and Ti ( 7). [Pg.277]

Reduction of metal oxides with hydrogen is of interest in the metals refining industry (94,95) (see Metallurgy). Hydrogen is also used to reduce sulfites to sulfides in one step in the removal of SO2 pollutants (see Airpollution) (96). Hydrogen reacts directiy with SO2 under catalytic conditions to produce elemental sulfur and H2S (97—98). Under certain conditions, hydrogen reacts with nitric oxide, an atmospheric poUutant and contributor to photochemical smog, to produce N2 ... [Pg.416]

The most important manganese(V) compound is K MnO, a key intermediate in the manufacture of potassium permanganate. Potassium manganate(V) is an easily crystallized salt obtained by reduction of potassium permanganate using sodium sulfite in strong sodium hydroxide solution. This was the first compound to be recognized as exclusively pentavalent. [Pg.514]

The reduction of alkyl-substituted siUcon and tin peroxides with sodium sulfite and triphenylphosphine has been reported (33,93). Alkyl-substituted aluminum, boron, cadmium, germanium, siUcon, and tin peroxides undergo oxygen-to-metal rearrangements (33,43,94), eg, equations 22 and 23. [Pg.109]

Rhenium oxides have been studied as catalyst materials in oxidation reactions of sulfur dioxide to sulfur trioxide, sulfite to sulfate, and nitrite to nitrate. There has been no commercial development in this area. These compounds have also been used as catalysts for reductions, but appear not to have exceptional properties. Rhenium sulfide catalysts have been used for hydrogenations of organic compounds, including benzene and styrene, and for dehydrogenation of alcohols to give aldehydes (qv) and ketones (qv). The significant property of these catalyst systems is that they are not poisoned by sulfur compounds. [Pg.164]

Uses. The dominant use of sulfur dioxide is as a captive intermediate for production of sulfuric acid. There is also substantial captive production in the pulp and paper industry for sulfite pulping, and it is used as an intermediate for on-site production of bleaches, eg, chlorine dioxide or sodium hydrosulfite (see Bleaching agents). There is a substantial merchant market for sulfur dioxide in the paper and pulp industry. Sulfur dioxide is used for the production of chlorine dioxide at the paper (qv) mill site by reduction of sodium chlorate in sulfuric acid solution and also for production of sodium dithionite by the reaction of sodium borohydride with sulfur dioxide (315). This last appHcation was growing rapidly in North America as of the late 1990s. [Pg.148]

Chemical Properties. Anhydrous sodium sulfite is stable in dry air at ambient temperatures or at 100°C, but in moist air it undergoes rapid oxidation to sodium sulfate [7757-82-6]. On heating to 600°C, sodium sulfite disproportionates to sodium sulfate and sodium sulfide [1313-82-2]. Above 900°C, the decomposition products are sodium oxide and sulfur dioxide. At 600°C, it forms sodium sulfide upon reduction with carbon (332). [Pg.148]

Water Treatment. Sodium sulfite is an agent in the reduction of chlorine or oxygen in water. Dissolved oxygen in boiler water tends to enhance pitting and other types of corrosion. In boilers operated at below 4.82 MPa (700 psi), a residual concentration of 30 ppm of sodium sulfite is generally effective. Catalytic amounts of cobalt are often added to accelerate the reaction of oxygen with sulfite (321,322) (see Water, industrial water treatment). [Pg.149]

In removing excess free chlorine from municipal or industrial water and from wastewater, sodium sulfite competes with bisulfite or sulfur dioxide. Other commercial appHcations of sodium sulfite in wastewater treatment include the reduction of hexavalent chromium to the less toxic Cr " salts as well as the precipitation of silver and mercury. [Pg.149]

Dithionite is a stronger reducing agent than sulfite. Many metal ions, eg, Cu", Ag", Pb ", Sb ", and Bi ", are reduced to the metal, whereas TiO " is reduced to (346). Dithionite readily reduces iodine, peroxides, ferric salts, and oxygen. Some of the decolorizing appHcations of dithionite, eg, in clay bleaching, are based on the reduction of ferric iron. [Pg.150]

Addition of sodium dithionite to formaldehyde yields the sodium salt of hydroxymethanesulfinic acid [79-25-4] H0CH2S02Na, which retains the useful reducing character of the sodium dithionite although somewhat attenuated in reactivity. The most important organic chemistry of sodium dithionite involves its use in reducing dyes, eg, anthraquinone vat dyes, sulfur dyes, and indigo, to their soluble leuco forms (see Dyes, anthraquinone). Dithionite can reduce various chromophores that are not reduced by sulfite. Dithionite can be used for the reduction of aldehydes and ketones to alcohols (348). Quantitative studies have been made of the reduction potential of dithionite as a function of pH and the concentration of other salts (349,350). [Pg.150]

Ana.lytica.1 Methods. Various analytical methods involve titration with oxidants, eg, hexacyanoferrate (ferricyanide), which oxidize dithionites to sulfite. lodimetric titration to sulfate in the presence of formaldehyde enables dithionite to be distinguished from sulfite because aldehyde adducts of sulfite are not oxidized by iodine. Reductive bleaching of dyes can be used to determine dithionite, the extent of reduction being deterrnined photometrically. Methods for determining mixtures of dithionite, sulfite, and thiosulfates have been reviewed (365). Analysis of dithionite particularly for thiosulfate, a frequent and undesirable impurity, can be done easily by Hquid chromatography (366). [Pg.151]

Electrolytic reduction with a mercury or platinum electrode produces equimolar amounts of sulfide and sulfite ... [Pg.26]

Dithionites. Although the free-dithionous acid, H2S2O4, has never been isolated, the salts of the acid, in particular zinc [7779-86-4] and sodium dithionite [7775-14-6] have been prepared and are widely used as industrial reducing agents. The dithionite salts can be prepared by the reaction of sodium formate with sodium hydroxide and sulfur dioxide or by the reduction of sulfites, bisulfites, and sulfur dioxide with metallic substances such as zinc, iron, or zinc or sodium amalgams, or by electrolytic reduction (147). [Pg.149]

In hair coloring a light ash blond shade may require as Httie as 0.5—1% of intermediates, whereas a tme black may require up to about 5%. In principle, the formulator blends precursors that yield red, blue, and yellow dyes. The base in which the components are dissolved or suspended is similar to that used in simple bleaches and may include alkanolamides, various types of surfactants, thickening agents, and solvents. Removal of undesirable dyes is achieved by treating the discolored hair with a powerful reductant of the sulfite family. [Pg.302]

Another important reduction process is that of aryldiazonium salts with sulfite/bisulfite at controlled pH to produce aryUiydrazines. AryUiydrazines are important intermediates for the preparation of pyrazolones and indoles. [Pg.289]

Arylalkylsulfones ate important intermediates obtained by alkylation of arylsulfinic acids. The latter ate obtained by reduction of the corresponding sulfonyl chloride. This reduction process is simple and of general appHcation involving the addition of the isolated sulfonyl chloride paste to excess aqueous sodium sulfite followed by salting-out the product and isolation. With mote rigorous reduction conditions, such as zinc/acid, sulfonyl chlorides ate reduced through to aryknercaptans, eg, 2-mercaptonaphthalene is manufactured from naphthalene-2-sulfonyl chloride. [Pg.289]

The procedure given above for the preparation of methanesulfonyl cyanide essentially is a combination of the sulfite reduction of a sulfonyl... [Pg.90]

The parent acid has no independent existence and has not been detected in aqueous solution either. Sodium dithionite is widely used as an industrial reducing agent and can be prepared by reduction of sulfite using Zn dust, Na/Hg or electrolytically, e.g. ... [Pg.720]

The removal of each milligram of oxygen requires about 8 mg of sodium sulfite, so that the dose should be adjusted to suit the amount of oxygen introduced, which corresponds roughly to 80mg/l of cold make-up. A high level of condensate return therefore reduces the scavenger demand, and this is not only an economy in itself but can also mean a considerable reduction in the amount of total dissolved solids introduced into the boiler with the feedwater. [Pg.477]


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