The specific heat C p at constant pressure, the shear viscosity s , and the mutual diffusion coefficient D of the 2,6-dimethylpyridine-water mixture of critical composition have been measured in the homogeneous phase at various temperatures near the lower critical demixing temperature T c . The amplitude of the fluctuation correlation length 0 = ͑0.198± 0.004͒ nm has been derived from a combined evaluation of the s and D data. This value is in reasonable agreement with the one obtained from the

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... amplitude A + = ͑0.26± 0.01͒ J/͑g K͒ of the critical term in the specific heat, using the two-scale-factor universality relation. Within the limits of error the relaxation rate ⌫ of order parameter fluctuations follows power law with the theoretical universal exponent and with the amplitude ⌫ = ͑25± 1͒ ϫ 10 9 s −1 . No indications of interferences of the critical fluctuations with other elementary chemical reactions have been found. A noteworthy result is the agreement of the background viscosity b , resulting from the treatment of s and D data, with the viscosity s ͑ =0͒ extrapolated from high-frequency viscosity data. The latter have been measured in the frequency range of 5 -130 MHz using a novel shear impedance spectrometer.