No abstract

No abstract

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.

Earlier studies of the dissociation constants of monoethanolammon iu m a nd diethanolammonillm ions and the thermodynamic con s tants for t he dissociation processe have been supple mented by a simi lar study of triethanolammoni um ion from 0° to 50° C . The dissociation con stant (II. bh) is gi ven by the formu la -log K b,, = 1341.l6j T + 4.6252 -0.0045666T where T is in degrees Kelvin. The order of acidic strcngths of t he ion s is as folloll" s: Triethanolamm.onium > diethallolammo nium > rnonethanolam mooium.Converse ly, rnonoetha nolamin e is the stron gest of the three bases. The thermodyna mic constants for the dis ociation of one mole of t rietha nolammonium ion in the standard state at 25° C are as fol lows: H eat contcnt cha nge

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.