Sodium sulfite reducing agent

Sodium hydrosulfite Sodium metabisulfite Sodium sulfite Sodium thioglycolate reducing agent, phosphors Stannous chloride anhydrous... 

Removal of brine contaminants accounts for a significant portion of overall chlor—alkali production cost, especially for the membrane process. Moreover, part or all of the depleted brine from mercury and membrane cells must first be dechlorinated to recover the dissolved chlorine and to prevent corrosion during further processing. In a typical membrane plant, HCl is added to Hberate chlorine, then a vacuum is appHed to recover it. A reducing agent such as sodium sulfite is added to remove the final traces because chlorine would adversely react with the ion-exchange resins used later in the process. Dechlorinated brine is then resaturated with soHd salt for further use. 

Photography. Sodium sulfite is useful as a reducing agent in certain photographic fixing baths, developers, hardeners, and intensifiers (334). However, the principal use is as a film preservative and discoloration preventative (see Photography). 

The reducing agents generally used in bleaching include sulfur dioxide, sulfurous acid, bisulfites, sulfites, hydrosulfites (dithionites), sodium sulfoxylate formaldehyde, and sodium borohydride. These materials are used mainly in pulp and textile bleaching (see Sulfur compounds Boron compounds). 

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). 

Chromium Removal System. Chlorate manufacturers must remove chromium from the chlorate solution as a result of environmental regulations. During crystallization of sodium chlorate, essentially all of the sodium dichromate is recycled back to the electrolyzer. Alternatively, hexavalent chromium, Cr, can be reduced and coprecipitated in an agitated reactor using a choice of reducing agents, eg, sodium sulfide, sulfite, thiosulfate, hydrosulfite, hydrazine, etc. The product is chromium(III) oxide [1333-82-0] (98—106). Ion exchange and solvent extraction techniques have also... 

A dichromate or chromate solution is reduced under pressure to produce a hydrous oxide, which is filtered, washed, and calcined at 1000°C. The calcined oxide is washed to remove sodium chromate, dried, and ground. Sulfur, glucose, sulfite, and reducing gases may be used as reducing agent, and temperatures may reach 210°C and pressures 4—5 MPa (600—700 psi). 

Conversely, sulfites can act as oxidants in the presence of strong reducing agents e.g. sodium amalgam yields dithionite, and formates (in being oxidized to oxalates) yield thiosulfate ... 

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. ... 

Sulfinic acids can be prepared by reduction of sulfonyl chlorides. Though mostly done on aromatic sulfonyl chlorides, the reaction has also been applied to alkyl compounds. Besides zinc, sodium sulfite, hydrazine, sodium sulfide, and other reducing agents have been used. For reduction of sulfonyl chlorides to thiols, see 19-57. 

Highly active CuCl catalysts for the direct process of methylchlorosilane synthesis were prepared by reducing Cu with a sodium sulfite solution in the presence of dispersing agents. Several well-known dispersants, e.g. SDBS, were used in this study. When SDBS was used, a catalyst in the form of small flakes was obtained that gave the best performance in reactivity, product selectivity and silicon conversion. This provides a convenient way to prepare the CuCl catalyst for use in industrial production. 

Many of the modifications of the pyrazolone antiinflammatory agents are intended to increase the limited hydrophilicity of the parent molecules. Reaction of aminopyrine (157) with formaldehyde and sodium hydrogen sulfite affords dipyrone (158). The first step can be rationalized as an Eschweiler-Clark type N-methylation reaction, with bisulfite acting as the reducing agent. The resulting mono N-methyl analogue of 157 then apparently forms the sulfite adduct of the carbinolamine of formaldehyde. 

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