SOLUTIONS OF SULPHUR TRIOXIDE IN FLUOROSULPHURIC ACID AND CHLOROSULPHURIC ACID: RAMAN AND N.M.R. SPECTROSCOPIC EVIDENCE FOR THE FORMATION OF HALOGENOPOLYSULPHURIC ACIDS
The Raman spectra of solutions of sulphur trioxide in fluorosulphuric acid and chlorosulphuric acid have been examined. By comparing the spectra with those of the polysulphuryl halides and the polysulphuric acids the formation of the halogen-substituted polysulphuric acids HS2O6F, HS3O9F, HS2O6Cl, and HS3O9Cl is proved and some evidence is obtained for higher polyacids such as HS4O12F and HS4O12Cl. The fluorine n.m.r. spectra of solutions of sulphur trioxide in fluorosulphuric acid have also been investigated: they provide supporting evidence for the formation of fluoropolysulphuric acids. Vibrational frequencies diagnostic of the ions S2O6F− and S2O6Cl− have been obtained from the Raman spectra of fluorosulphuric acid solutions containing both sulphur trioxide and sodium fluorosulphate, and chlorosulphuric acid solutions containing both sodium chlorosulphate and sulphur trioxide.