Chlorate-sulfite reaction

Nagy, I. P. Pojman, J. A. 1993. Multicomponent Convection Induced by Fronts in the Chlorate-Sulfite Reaction, J. Phys. Chem. 97, 3443-3449,... 

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. 

Zinc forms a wide variety of other salts, many by reaction with the adds, though some can only be obtained by fusing the oxides together. The salts include arsenates (ortho, pyro, and meta), the borate, bromate, chlorate, chlorite, various chromates, cyanide, iodate. various periodates, permanganate, phosphates (ortho, pyro, meta, various double phosphates 1. die selenate, selenites, various silicates, fluosilicate. sulfate, sulfite, and duocyanate. 

More recently, it wras shown by H. Taube that if the reduction of chlorate by sulfite is carried out in water enriched with 180, only a minor amount of 180 appears in the resulting sulfate. This means that the reaction takes place largely by direct transfer of oxygen atoms from chlorine to sulfur without participation of solvent ... 

We have seen, for example (p. 80), that oxidation of SO72 by ClOj" involves the transfer of an oxygen atom from chlorate to sulfite that is, the reaction is a nucleophilic substitution by sulfite on one of the oxygen atoms of chlorate. 

The selectivity of the test is quite limited, even compared to the specificity seen in the identification test for chlorides. In the identification three criteria have to be fulfilled to qualify for a positive reaction. The unknown should give a white (curdled) precipitate formed upon addition of silver nitrate, which is insoluble in dilute nitric acid but redissolves in ammonia. In the limit test 2.4.4. Chlorides any substance capable of giving a white or weakly colored precipitate in dilute nitric acid will give a response like chloride, and this should be remembered in case of an xmexpected result. For the sake of example the following ions and substances are capable of giving a false positive reaction bromide, iodide, bromate, iodate, sulfite, chlorate, oxalate, and benzoate. In addition to this a variety of more complex organic substances are likely to precipitate, for example, alkaloids. 

A solution initially contains sulfite-bisulfite and chlorate with the pH indicator bromophenol blue. No reaction occurs until some 3 M sulfuric acid is added. The solution rapidly turns yellow as the pH drops. 

Chemists have characterized two classes of redox reactions atom transfer and electron transfer. The classic example of atom transfer involves the aqueous oxidation of sulfite ion by chlorate ion in which atoms initially bound to chlorine are found bound to the product sulfate, which thus precludes exchange of oxygen with water during the process ... 

Bromate and iodate salts are prepared on a much smaller scale than chlorates. Under appropriate conditions, these ions undergo oscillating chemical reactions known as chemical clocks. The best known clock reaction is observed when an acidified solution of sodium sulfite (Na2S03) is mixed with an excess of iodate in the presence of starch indicator. After a suitable induction period allowing for sodium sulfite reduction of iodate to iodide [Eq. (44)], the blue, starch-iodine color periodically appears and disappears as the iodide is oxidized to iodine [Eq. (45)], and the iodine is reduced back to iodide [Eq. (46)]. 

Many redox reactions involving oxyanions and molecular oxides seem to involve a transfer of oxygen atoms as well as a transfer of electrons. A typical example is the oxidation of sulfite ion by chlorate ion,... 

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