The complex dielectric permittivity of aqueous sodium sulfate solutions (0.
025 less than or equal to c/mol dm(-3) less than or equal to 1.6) has been
determined in the frequency range 0.2 less than or equal to v/GHz less than
or equal to 20 with a commercial dielectric measurement system based on a
vector network analyzer. The spectra were supplemented with interpolated li
terature data at 12 less than or equal to v/GHz less than or equal to 89. T
o fit the complex permittivity spectra, a superposition of three Debye rela
xation processes was necessary. The slow and intermediate dispersion steps
are assigned to the tumbling motion of doubly solvent-separated (2SIP) and
solvent-shared (SSIP) NaSO4- ion pairs, respectively. The fast process, of
amplitude S-3, is due to the collective relaxation of the solvent. Effectiv
e solvation numbers were deduced from the effect of Na2SO4 concentration on
S-3. From the ion-pair dispersion amplitudes, S-1 and S-2, the concentrati
ons c(2SIP) and c(SSIP), and thus the overall stoichiometric stability cons
tant, beta(NaSO4-), were determined.