Knowledge Bank

It has been suggested from transport and proton magnetic resonance studies that in molten $Ca(NO3)2$ $4H2O$ and its mixtures with $KNO3$ (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, $Ca(H2O)4$, and that the $Ca+2$ion is selectively hydrated in the mixtures with $KNO3$. 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 $Ca(NO3)2$ $4H2O-KNO3$ mixtures (up to 70 mole % $KNO3$). 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 $NO3-$ion spectrum and the ($3000-3600cm-1$) water band region and discussed from current viewpoints of ionic interactions and water structure.