Temperature Dependence Of Rho Research Articles

Densities, Viscosities, and Electrical Conductivities of Pure Anhydrous Reline and Its Mixtures with Water in the Temperature Range (293.15 to 338.15) K

Density (rho), dynamic viscosity (eta), and electrical conductivity (kappa) of the deep eutectic solvent (DES) reline, composed of choline chloride (ChCl) and urea in a 1:2 molar ratio, and its mixtures with water, covering the entire miscibility range, were studied at T = (293.15 to 338.15) K. Compared to many previous studies, reline purity was significantly improved by using ultrapure urea and ChCl recrystallized from ethanol. For the investigated DES samples the mass fraction of residual water was <0.00035. This allowed checking the influence of water traces and impurities on the physicochemical properties of pure reline. It was found that the presence of small amounts of water (w(H2O) < 0.0081) only negligibly decreased reline density, not exceeding 0.14% compared to the dry sample. However, for the same amount of water decreased by similar to 36% at 298.15 K. The temperature dependence of rho was well fitted by a quadratic expression, whereas eta(T) and kappa(T) were found to follow the empirical Vogel-Fulcher-Tammann equation. For the aqueous mixtures excess properties of molar volume (V-E) and viscosity (eta(E)) showed only minor variation with composition, suggesting rather weak interactions between water and the constituents of reline. However, V-E and eta(E) depended significantly on temperature, indicating a significant contribution of H-bonding to the inherent reline structure. Similar to conventional ionic liquids, the conductivity of aqueous reline showed a broad maximum at the reline mole fraction of x(1) approximate to 0.18 associated with the border between aqueous solutions of individual reline components and reline/water mixtures. The Walden plot classifies reline as a poor ionic liquid.

Further evidence of higher order correlation effects on properties of liquid mercury alloys

In order to study the origin of the minimum at a few at.% solute concentration in the isotherm of the thermoelectric power Q versus composition of liquid mercury alloys (the 'minimum in Q'), the electrical resistivity rho of liquid Hg-In alloys and Hg-Sn alloys has been measured precisely as a detailed function of composition. The present measurements indicate that the temperature dependence of rho , delta rho / delta T, shows a hump at about 5 at.% In for liquid Hg-In alloys in contrast to a smooth decrease observed for liquid Hg-Sn alloys; the former system shows the 'minimum in Q' and the latter does not. These experimental facts suggest that the higher order correlation effect stressed already by the present authors is important in understanding the origin of the 'minimum in Q'.

Evidence of higher order correlation effects on properties of liquid mercury alloys

In order to study the origin of the minimum at a few at.% solute concentration in the isotherm of the thermoelectric power Q versus composition of liquid mercury alloys (the 'minimum in Q'), the electrical resistivity rho of liquid Hg-In alloys and Hg-Sn alloys has been measured precisely as a detailed function of composition. The present measurements indicate that the temperature dependence of rho , delta rho / delta T, shows a hump at about 5 at.% In for liquid Hg-In alloys in contrast to a smooth decrease observed for liquid Hg-Sn alloys; the former system shows the 'minimum in Q' and the latter does not. These experimental facts suggest that the higher order correlation effect stressed already by the present authors is important in understanding the origin of the 'minimum in Q'.

Negative temperature coefficients of electrical resistivity: the divalent liquid metals Eu, Yb and Ba

The electrical resistivities, rho , of Eu, Yb and Ba have been measured at high temperatures. In solid Yb and Ba rho varies linearly with temperature. This is contrary to some previous results. Both metals show a large percentage increase of rho on melting. The temperature dependence of rho in Eu is nonlinear and there is a smaller percentage change on melting. The resistivities of liquid Eu and Ba are larger than those of any other liquid metals. Negative temperature coefficients of resistivity are observed for all three metals in the liquid state. These results and those obtained in our earlier measurements on alloys of rare earth metals are discussed in the context of existing theories. The authors suggest that even in the liquid rare earth metals and their alloys an interpretation involving the liquid structure factors and the effective valences of the components may still provide a reasonable qualitative explanation of the behaviour of the resistivity. The occurrence of negative temperature coefficients in other disordered metallic systems is also commented on.