A Spectroscopic Study of Mn(NO3)2-H2OS ystems

Abstract

For a study of interactions between ions and those between ions and water in concentrated electrolyte solutions of water and an electrolyte, the chemical behaviors of cation, anion and water in Mn(NO₃)₂-H₂O systems were investigated with infrared, laser Raman, near infrared and visible spectroscopies for the binary systems from the dilute solution to such a concentrated solution as 9.6 mol/l.
An analysis of Raman bands at 720-750 cm^-1 with a curve resolver showed that interactions between NO₃^- and Mn²⁺changed with increasing concentration and that the transition of the free coordinate into unidentate and bidentate coordinations took place at 3.0 mol/l and 6.0 mol/l respectively. Effect of the concentration of the electrolyte on NIR spectra for the combination bands of -H₂O indicated that the breakdown of the structure of the bulk water increased with increasing concentration of the electrolyte and that the amount of coordinate water increased with the increase of the concentration. Results of visible spectroscopy suggested that the covalency in the interaction of Mn²⁺-NO₃^- increased in concentrations higher than 6.0 mol/l.
These results suggest that Mn(NO₃)₂-H₂O systems have interactions depending on co ncentration, 0-3 mol/l, 3-6 mol/l and higher concentrations than 6 mol/l.