Tracer diffusion coefficients of tritiated water in mixtures of 2,6-lutidine-water have been measured over the entire concentration range at E=1.1XlO-4 below the critical point using the diaphragm cell. No anomaly was detected. The shear viscosity coefficients were measured across the entire concentration range at E=2.246XlO-2 , 1.268 X 10-2 , 7.8XlO-5 by a closed capillary viscometer. The observed anomaly in the region of the critical point was further characterized by studying the temperature dependence of the viscosity of a mixture at critical composition. These data are discussed in terms of Kawasaki's modemode coupling theory.

The absolute fluorescence quantum yield of quinine bisulphate in aqueous 1N H2S04 with excitation at 366nm has been measured calorimetrically. A value of 0.561 is reported with an error conservatively estimated at 7 %.

Light scattering measurements were performed on the binary liquid mixture carbon tetrachloride–perfluoromethylcyclohexane at its critical concentration and immediately above its critical consolute temperature. Measurements of time averaged intensities as a function of scattering angle and temperature distance from the critical consolute temperature, T−Tc, yielded the critical parameters γ = 1.220±0.018, ξ0 = 2.28±0.21 Å, and ν = 0.626±0.013. Here γ describes the temperature dependence of the susceptibility χ according to the relation χ∝ε−γ, where ε = (T−Tc)/Tc. ξ0 and ν characterize the correlation length with ξ = ξ0ε−ν, which is a measure of the spatial extent of local concentration fluctuations. These values of γ and ν agree well with the scaling and universality hypothesis. Time dependence of the intensity as a function of scattering angle and of T−Tc was determined by measuring the photocurrent autocorrelation function. These measurements yielded decay rates for concentration fluctuations. Combination of decay rates, correlation lengths, and viscosities allowed a direct comparison with the mode–mode coupling theory of Kawasaki. Excellent coincidence of theory and experiment was found except in the vicinity of Kξ = 1, where decay rates were high when compared to theory. K is the magnitude of the momentum transfer vector. Sources of error in the critical parameters obtained from light scattering intensity measurements were analyzed in detail. A useful equation is derived which relates the actual scattering angle inside a cylindrical cell to eight experimental parameters including five ’’alignment’’ parameters which are subject to error. Graphical criteria are presented for estimating uncertainties in critical parameters γ, ξ0, ν, and η.

The electrical resistance of sealed solutions of isobutyric acid-water at the critical composition were measured in the reduced temperature range (ε = T/Tc − 1)3.3 × 10−7 ≤ ε ≤ 6.6 × 10−2 using a Jones ac bridge and lock-in amplifier. Temperatures were controlled and measured to ± 0.0001°C. The temperature derivative of the resistance exhibits a strong divergence very close to Tc so that dR/dT [inverted lazy s] ε−d, where 0.56 ≤ d ≤ 0.77 depending on which of the several methods of data analysis presented are used. A mechanism is proposed which relates this strong divergence to the weak anomaly in the shear viscosity near Tc.

Experimental data on the coexistence curves for nine binary liquid systems, which meet strict criteria of precision, purity of components, and experimental method, are analyzed in the neighb~rhood of the critical point. The data are examined in terms of a general equation of state which is nonanalytic at the critical point. The results of the computer analysis using weighted non-linear least squares procedures present evidence that some symmetry features of classical equations of state remain; and within the experimental errors in the data all systems are consistent with the critical exponent ,B = 0.34.The asymptotic behavior of the diameter is examined and evidence is provided for a curved diameter in some cases; however, it is concluded that the available data are not extensive enough to make a firm conclusion concerning the shape of the diameter. Experimental methods are briefly criticized and mention is made of the experimental direction that future work should take. Special attention is given to estimating the reliability of the conclusions that may be drawn from a given set of data.