Viscosity, electrical conductivity, shear relaxation time and Raman spectra of aqueous and methanolic sodium thiocyanate solutions

Measured viscosity, electrical conductivity, the shear relaxation time and the Raman spectra of aqueous and methanolic sodium thiocyanate solutions ar e reported as functions of concentration (0.0237 less than or equal to m(mo l kg(-1)) less than or equal to 19.685) and temperature (273.15 less than o r equal to T(K) less than or equal to 323.15). The non-Arrhenius temperatur e dependence of viscosity, electrical conductivity and shear relaxation tim e was analysed by using the Vogel-Tammann-Fulcher (VTF) equation. Variation of the By parameter of the VTF equation with concentration evoked some kin d of structural transition over a narrow concentration range. The concentra tion dependence of the viscosity and conductivity data was analysed by usin g the reported equations. In aqueous sodium thiocyanate solutions, the exis tence of the hydrated ions due to the ion-solvent interactions in the conce ntration range from dilute to 3.0 mol kg(-1), the solvent-separated and(or) the solvent-shared ion-pairs due to the competition between the ion-solven t and the ion-ion interactions from 3.0 to 6.2 mol kg(-1) and the contact i on-pairs due to the ion-ion interactions beyond 6.2 mol kg(-1) govern the t ransport processes. In methanolic sodium thiocyanate solutions, from dilute to similar to3.9 mol kg(-1), free and hydrogen bonded SCN- and beyond simi lar to3.9 mol kg(-1), solvent-shared ion-pairs dominate in the solutions an d govern the transport processes. The Raman spectra recorded for the nu (C- N) and nu (C-S) stretching frequencies shifted to higher frequency regions and reveal the existence of the complex adduct of SCN- with the solvent mol ecule. (C) 2001 Elsevier Science B.V. All rights reserved.