A relative transient hot-wire apparatus for the measurement of the thermal conductivity of electrically conducting liquids is described. The instrument consists of a single glass capillary filled with mercury to act as an insulated hot wire. The resistance change in the wire with respect to time is used to obtain the thermal conductivity of the liquid surrounding the wire with an estimated accuracy of ±2%. The most significant advantage of the liquid metal filled glass capillary is its increased temperature limit compared to other types of transient hot-wire cells. The use of the new method at temperatures up to 493 K is shown for several aqueous systems, and new data are reported for propionic acid + water mixtures.

The viscosity and thermal conductivity of acetic acid-water mixtures were measured over the entire composition range and at temperatures ranging from 293 to 453 K. Viscosity measurements were performed with a high-pressure viscometer and thernaal conductivity was measured using a modified transient hot-wire technique. A mercury filled glass capillary was used as the insulated hot wire in tile measurements. The viscosity data showed unusual trends with respect to composition. At a given temperature, the viscosity was seen to increase with increasing acid coqcentration, attain a maximum, and then decrease. The thermal conductivity, on the other hand, decreased monotonically with acid concentration. A generalized corresponding-states principle using water and acetic acid as the reference fluids was used to predict both viscosity and thermal conductivity with considerable succes.

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A simple extension of the rough hard-sphere theory is proposed to describe the thermal conductivity and viscosity of a wide variety of polar compounds. The method is based on the known transport properties of a smooth hard-sphere system together with a temperature-dependent hard-core volume and coupling parameters to account for deviations from true smooth hard-sphere behavior. A key advantage of the method is the ability to simultaneously correlate self-diffusion, viscosity, and thermal conductivity using a common characteristic volume V 0 for each compound. Thus, information about V 0 obtained from one transport property can be applied to calculate the other properties. The model is also well suited for extension to temperature and pressure conditions outside those at which experimental data are available. Results for 58 polar liquids in the temperature range from 293 to 493 K are presented with a maximum error of 5.0% for viscosity and 2.9% for thermal conductivity. Model parameters for a homologous series of compounds can be expressed as smooth functions of the size, allowing the prediction of the transport properties for compounds for which data are presently not available.

A new method is presented for the prediction of the transport properties (viscosity, thermal conductivity, and diffusion coefficient) of liquids. The method is based on the rough hard sphere theory of Chandler and incorporates the recent molecular dynamics results for Lennard-Jones fluids reported by Heyes. The Lennard-Jones parameters and the effective hard sphere diameter required in the calculations were determined from a knowledge only of the density-temperature behavior of the fluid at atmospheric pressure using the Ross variational perturbation method. Analytical expressions are presented for the transport properties of the n-alkanes, and comparisons are shown between calculations and experiment. The results generally agree with published results within experimental error. The analytical expressions also allow the transport properties of the alkanes to be calculated a t conditions of temperature and pressure where direct measurements would be difficult.