Conductivity measurements were performed on phosphotungstic and silicotungstic aqueous electrolyte solutions. The conductivity obtained from complex impedance plots had non-Arrhenius dependence on temperature and could be fit by the Vogel-Tamman-Fulcher expression, T 1/2 exp͓Q c /(T-T o )͔. Conductivities reached 0.257 and 0.32 S cm Ϫ1 at 298 K for the 60 wt % phosphotungstic and silicotungstic solutions, respectively. Low concentration silicotungstic solutions obeyed the Kohlrausch relation

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... owing for the determination of infinite dilution molar conductivity, 1637 S cm 2 mol Ϫ1 , with the anionic species 1 4 ͓SiW 12 O 40 ͔ 4Ϫ having a molar conductivity of 237 S cm 2 mol Ϫ1 . The diffusion coefficient of the anionic species at 303 K was 4.8 ϫ 10 Ϫ6 cm 2 s Ϫ1 with a hydrodynamic radius of 5.78 Å. Analysis of the charge transference numbers indicated that the conductivity was predominantly protonic, and suitable for room-temperature fuel cells.