Ion-ion-solvent interactions in solution. Part 4. - Raman spectra of aqueous solutions of some nitrates with monovalent cations

The profile of the band due to the symmetric stretching of the nitrate ion in the Raman spectra of solutions of NHNO, MeN·NO, LiNO, KNO and RbNO has been component analysed. For the cations NH and MeN only one component was present. The bandwidth indicates that the ammonium ion causes enhanced dephasing while the tetramethylammonium ion produces essentially no perturbation. Solutions of LiNO gave evidence of four concentration-dependent species identified as aquated ions, solvent-separated ion pairs, contact ion pairs and ion aggregates. Solutions of KNO and RbNO gave evidence of three species identified as aquated ions, ion pairs and ion aggregates. It was not possible to distinguish between contact ion pairs and solvent-separated ion pairs. Association quotients calculated for LiNO solutions were K(1 mol dm) = 1.34 dm mol and K (6 mol dm) = 1.5, for KNO solutions K(1 mol dm) = 2.0 dm mol and for RbNO solutions K(1 mol dm) = 1.0 dm mol