Search for a structural change in concentrated sodium sulfate solutions around the transition point temperature using the charge transfer to solvent spectrum of lodide ion as a probe

Abstract

Claims have been made that aqueous sodium sulfate solutions exhibit an anomalous temperature dependence close to the transition point of the solid decahydrate (Na₂SO₄·10H₂O), viz., 32.38°C. In studies of dilute solutions these claims have been queried. Concentrated solutions, where this effect might be more readily detected, have not been investigated. A very accurate analysis of the shift of the charge transfer to solvent spectrum of iodide, a sensitive probe of its environment, (6×10⁻⁵ M) in concentrated (1 and 2 M) sodium sulfate solutions, as a function of temperature has not evinced any support for a structural change in solution on traversing the transition point temperature.