Raman Spectra of Aqueous Solutions of Indium Sulfate, Nitrate, and Perchlorate

Abstract

For a series of metal-ion sulfate solutions investigated, only In3+ showed Raman spectral evidence of association with SO4=. The evidence consisted of the appearance in indium sulfate solutions of four new polarized lines in the Raman spectrum. Three of these were accounted for in terms of C3v symmetry for the bound sulfate ion and the assignment thus was: v1(A1)=1125 cm—1, v2(A1)=1000 cm—1, v3(A1)=650 cm—1. The fourth new line, at 255 cm—1, was also present (at 270 cm—1) in indium nitrate solutions and thus assigned to an In–O stretching mode. Raman intensity data, particularly in mixed indium sulfate—indium perchlorate solutions, verified the new species as an indium—sulfate complex; however, these data did not permit a decision between the presence of InSO4+, In(SO4)2—, or a mixture of the two. The fact that the 255 cm—1 line was found to be highly polarized suggested that a linear In(SO4)2— species might be of major importance. Finally, all indium solutions, even those with ClO4— as the only anion, showed a broad polarized band near 400 cm—1 which probably resulted from hydrated In3+.