Study of the state of FeSO/sub 4/ x 7H/sub 2/O in water-methanol solutions in the presence of H/sub 2/SO/sub 4/ by spectral methods

The process of the stepwise formation of water-methanol solvates of FeSO/sub 4/ x 7H/sub 2/O and their complexes with sulfuric acid has been investigated spectrophotometrically. It has been shown that the position of the charge-transfer bands and their intensities depend on the composition of the solvent (the water:methanol ratio) and on the concentration of the acid. The complexation of FeSO/sub 4/ x 7H/sub 2/O with H/sub 2/SO/sub 4/ in methanol has been studied by the mole-ratio method. The formation of three types of complexes with different stoichiometric ratios of iron and the acid has been demonstrated. A dimeric structure with a sulfate bridge has been proposed for the solvated complex of iron with sulfuric acid on the basis of the electronic and IR spectra. The valence state of iron in the mixed water-methanol solvates and in the complexes with sulfuric acid has been determined by ESR.