Hydrogen sulfite species

Typically, the dithionite species disproportionates in aqueous media to afford the hydrogen sulfite and thiosulfonate nucleophiles.64 This finding suggests that sulfite esters (-0S02 ) and Bunte salts (-SS03-)65 could be formed upon iminium methide... 

In contrast to the dilute acid decomposition of thiosulfate where the equilibrium and sulfite are acted upon by acid, this is accomplished in the citrate process by the reaction of the various sulfite species with hydrogen sulfide. 

In the context of a food additive, sulfur dioxide refers to a mixture of oxospecies of sulfur in an oxidation state of (h-4), i.e., SO2, HSOJ, SO3, S2O5. Sulfite and hydrogen sulfite ions are formed by the ionization of the species H2SO3, which is more correctly written as SO2 H2O. In practice it is very difficult to provide a quantitative description of these ionic and nonionic forms in foods. To avoid ambiguity the term S(1V) is used to describe the mixture of sulfur species when it is not necessary or possible to identify the detailed composition. 

Ion-selective electrodes using a sulfur dioxide gassensing membrane probe have been developed into commercial models for the determination of sul-fur(IV) oxo-species. A typical procedure for the determination of free sulfur dioxide requires the probe to be immersed in a stirred solution at pH 1, whereas total sulfur dioxide requires the sample to be treated with strong alkali prior to acidification and analysis at pH 1. Molecular sulfur dioxide passes through the membrane into a solution of hydrogen sulfite ion and the pH of the SO2 H20/HS03 buffer can be determined with a glass electrode. 

Formation of addition compounds from species containing carbonyl groups has been exploited for the determination of organic compounds reacting with hydrogen sulfite ion in the presence of acetone, methanol, or acetic acid. Primary amines can be determined alone and in mixtures with secondary and tertiary amines by condensation with aldehydes such as salicylaldehyde and 4-dimethylaminocinnamalde-hyde. 

For dual alkali scrubbing, the major dissolved species are sodium chloride, sodium bisulfite, sodium sulfite, and sodium sulfate. If a separate prescrubber is provided for the removal of fly ash and hydrogen chloride before the removal of sulfur dioxide, then sodium chloride will not be present in the sulfur dioxide scrubber. 

Oxidized sulfur species occurring in natural waters (sulfate, sulfite, thiosulfate] do not interact with the platinum electrode when in the presence of H2S and the pH-Eh-E52- relations found were similar to the above relations. Thus, the unambiguous relations found between pH, Eh and E22- in aqueous solutions of hydrogen sulfide can be employed to characterize solutions and water samples where hydrogen sulfide is the only reduced sulfur species present. 

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