RAMAN SPECTRAL INVESTIGATIONS OF $Ca(NO_{3})_{2}.4H_{2}O-KNO_{3}$ MIX TURES

Abstract

It has been suggested from transport and proton magnetic resonance studies that in molten $Ca(NO_{3})_{2}$ $4H_{2} O$ and its mixtures with $KNO_{3}$ (where the water content is just sufficient to satisfy the first coordination sphere around cations) the results can be explained on the basis of the existence of large multivalent cations, $Ca(H_{2}O)_{4}$, and that the $Ca^{+2}$ion is selectively hydrated in the mixtures with $KNO_{3}$. As part of our studies on the nature of interactions in aqueous electrolyte solutions and in molten salts, we have investigated the Raman spectrum of $Ca(NO_{3})_{2}$ $4H_{2}O-KNO_{3}$ mixtures (up to 70 mole % $KNO_{3}$). The spectra were recorded with a Jarrell-Ash Laser-Raman spect rometer using $He-$Ne and $Ar^{+}$ion lasers as exciting sources. Results are reported for the band shape variations (intensity and polarization) as a function of concentration, relative to the $\nu_{3}$ and $\nu_{4}$ regions of the $NO_{3}^{-}$ion spectrum and the ($3000-3600 cm^{-1}$) water band region and discussed from current viewpoints of ionic interactions and water structure.