Dielectric relaxation of aqueous Na2CO3 solutions

Abstract

The complex dielec. permittivity of aq. sodium carbonate solns. (0.05≤c/mol L-1≤2.5) has been detd. in the frequency range 0.2≤ν/GHz≤20 at 25.0°C with a com. dielec. measurement system based on a vector network analyzer. A superposition of three Debye relaxation processes was necessary to fit the complex permittivity spectra. The slow and intermediate dispersion steps are assigned to double solvent sepd. (2SIP) and solvent-shared (SSIP) NaCO3-(aq) ion-pairs resp. The absence of contact ion-pairs was confirmed by Raman spectroscopy. The fast process is assigned to the collective relaxation of the solvent. Equil. consts. for the formation of NaCO3-(aq) were detd. from the ion-pair dispersion amplitudes. The effect of Na2CO3 concn. on the water dispersion amplitude allowed effective solvation nos. to be deduced.