Osman Mohamed, Mubarak El-Sayed (1987)
Spectroscopic and thermodynamic properties of some oxy-sulphur species.
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Raman and infrared activities of aqueous sulphur dioxide solution and of the sodium salts of dithionate, disulphite, sulphite, sulphate, bisulphate, thiosulphate, tetrathionate and dithionite ions have been investigated in the crystal and aqueous states. On the basis of the data obtained, the following conclusions have been derived gauche configuration with group symmetry satisfactorily describes the vibrational activities of the dithionate ion both in the solid and in the aqueous states. Some evidence for the existence of crystalline sodium bisulphite has been revealed. In addition to the well-known H-SO form of bisulphite, the HO-SO tautomer has been identified in a very significant amount in aqueous disulphite solution. Employing progressive dilution measurements, characteristic bands of the, H-SO and HO-SO ions and of the constituent thionate and thionite units of disulphite have been assigned. The non-existence of the oxygen bridged disulphite ion and of the lithium, sodium and potassium salts of bisulphite have been rationalised. Eight bands have been identified with the HO-SO isomer of bisulphite, and on the basis of C group symmetry they have been assigned the infrared activity of the sulphate ion has revealed that even in the free state the ion does not assume full tetrahedral symmetry. Some fundamental vibrations of the bisulphate ion in the high frequency region have been re-assigned. The vibrational activities of the tetrathionate ion have been analysed in terms of two thiosulphate groups held together by an S-S bond. Its fundamental modes have been assigned on the basis of group symmetry. The vibrational spectra of the dithionite ion in aqueous solutions strongly suggests C-gauche symmetry. No evidence for adoption of the trans or the planar structure has been found. Thiosulphate has been identified among the disproportionation products of the dithionite ion. Its formation has been confirmed by ultraviolet spectroscopy. An auto-oxidation process involving free radicals and proceeding at a low rate has been suggested to account for its formation. Sulphurous acid, H2SO4 has been detected in a significant amount in standing aqueous sulphur dioxide solutions. Both of the tautomeric forms, HO-SO-OH and H-30-OH, have been1identified, and in addition to the bisulphite isomers, the formations of the sulphite, sulphate, bisulphate and of the dithionate ions have been indicated in such standing systems. G group symmetry has been assigned to both of the sulphurous acid isomers. Photographic fixation reactions have been calorimetrically investigated, and on the basis of the data derived the following points have been elucidated: using the above value for A
aq),the standard molar enthalpies of formation of Na
(aq) have been evaluated tofixation is an irreversible, penta-stageprocess which involves the following set of sequential equations. The structures of the above three silver-thiosulphate complexes have been elucidated on the basis of the spectral measurements performed, and that of Ag
has beendiscussed in terms of the constituent Ag
S and SO
units.The aqueous solubilityof sodium dithionate dihydrate crystalshas been determined. From the temperature coefficient of solubility, the entropy and the differential heat of solution have been evaluated to be 55.45 J raol r and 16.
8 kJ mol respectively.
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Institution: University of London, Royal Holloway and Bedford New College (United Kingdom).