Dithionic acid, salts

Disulfur dinitride, 6 126 Disulfur pentoxydiehloride, 3 124 analysis of, 3 126 Dithiocarbamates, of selenium(II) and tellurium(II), 4 91 Dithionic acid, salts of, 2 167 Dithionite ion, formation of, from sulfur dioxide by sodium hydride, 5 13... 

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). 

In dithionic acid and dithionates, 8205 , the oxidation state of the 2 8 atoms has been reduced from VI to V by the formation of an 8-8 bond (Table 15.18, p. 705). The free acid has not been obtained pure, but quite concentrated aqueous solutions can be prepared by treatment of the barium salt with the stoichiometric amount of H28O4 ... 

Sodium hydrosulfite Dithionous acid, disodium salt (8,9) (7775-14-6)... 

The Dithionates or Hyposulphates.—These salts, like the nitrates, are all soluble in water only normal salts are known.4 They may be obtained by neutralising dithionic acid solution with the hydroxide of the base, and also by double decomposition between barium dithionate solution and the sulphate of the base, or between manganese dithionate solution and the hydroxide of the base 5 also by methods on pp. 206-8. 

For the constitution and estimation of dithionic acid and its salts, see later (pp. 221-4.). 

This conclusion is drawn from the observed fact that the dithionic acids, on the electrolysis of their alkali salts, actually give acid supersulphides which correspond with the superoxides ... 

Dithionous acid, H2S2O4, is not obtainable as a pure compound, but several salts of the acid are known. The acid formally contains sulfur(III), and this suggests reduction of sulfites as a method of preparation. Such a process is illustrated in the following equation ... 

SYNS DITHIONOUS acid, zinc salt (1 1) ZINC HYDROSULFFTE ZINC HYDROSULFITE (DOT)... 

In acidic solutions, dithionic acid decomposes to sulphate and sulphur dioxide at rates which are readily measured (Table 26) . The reaction is of first order at defined acidity and the rate increases, but not proportionately, with acid concentration. The authors have favoured an interpretation in terms of undissociated H2S2O6. Salt effects and solvent deuterium effects are in general agree-... 

Dithionic acid appears in a solution of sulphurous acid oxidised by finely divided MnOg. From this, baryta precipitates all the sulphur-containing anions except dithionate, and, when the excess of Ba + has been precipitated by H2SO4, only 112820 is left in the solution. Although conductance measurements show the acid to be dibasic, acid salts are unknown. Dithionates are soluble in water and, unlike salts of the higher thionic acids, are not decomposed by sulphites and sulphides. 

Pyrazolin-5-ones form complexes with both inorganic and organic compounds much more readily than do the 2-pyrazolin-5-ones. The most extensive series of complexes is that formed with a variety of metallic salts. Antipyrine (2,3-dimethyl-l-phenyl-3-pyrazolin-5-one) forms a series of complexes with salts of divalent, trivalent and tetra-valent metals. Two molecules of antipyrine form a complex with one molecule of copper, cadmium, cobalt and zinc salts.266,866,1116 Complexes prepared from metallic nitrates are usually hydrated.1322 There also exists a series of complexes in which three molecules of antipyrine form a complex with one or two molecules of metallic salts. Such complexes form with two molecules of simple ferric salts272 or with one of complex iron cyanides.608 Nitrates of thorium, lanthanum, cerium and samarium also give such complexes.841 This ratio also occurs in some antipyrine complexes with cadmium and zinc thiocyanate.266 A number of salts of rare earths and iron which have complex anions such as thiosulfate, thiocyanate, dithionic acid and complex iron cyanides form complexes in which six molecules of antipyrine are present.405,408 608,841,950 Stannic chloride forms salts containing three or four molecules of antipyrine and hydrochloric acid.46... 

Salts of the thiolate anions represented in Equation (10.49) combine with phosgene with the loss of the sulfur, rather than the loss of the oxygen atom [317]. Reaction between COClj and the anion of the corresponding dithionic acid, however, gives the readily isolated product of Equation (10.50) [317]. 

Although we show the structure of dithionous acid in Table 15.8, only its salts are known and these are powerful reducing agents. Dithionite is prepared by reduction of sulfite in aqueous solution (equation 15.93) by Zn or Na amalgam and possesses eclipsed structure 15.48. 

Dithionic acid is another sulfur oxoacid that is only known in aqueous solution (in which it behaves as a strong acid) or in the form of salts containing the dithionate, [8205] , ion. 8uch salts can be isolated as crystalline solids and... 

Be0.2S203+i4H20. Basic salt, colorless gummy mass. Loses H2O and SO2 on heating. Made by carefully evaporating a solution of Be (OH)2 in dithionic acid. (Probably an indefinite solid solution). 

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