A free-volume and friction viscosity model is presented versus pressure and temperature, valid for both gaseous and dense fluids. This model involves only three adjustable parameters for each pure compound. It is able to represent the gas-liquid transition and the behavior in the supercritical conditions. The model has been successfully applied to methane (885 data points for 0.01< or =P< or =200 MPa and 90.7< or =T< or =600 K) and to propane (1085 data points for 0.01< or =P< or =200 MPa and 90< or =T< or =600 K) in the gaseous and dense states (average absolute deviation is 2.59% for methane and 2.50% for propane, with maximum deviation of 14.8% for methane and 9.19% for propane). It has also been applied to hexane, octane, dodecane, benzene, trans-decaline, and 2,2-dimethylpropane (903 data points) in a large pressure range (up to 505.5 MPa). Considering these compounds the maximum deviation is 19.5% (for octane) and the average deviation is 3.51% in the worst case (dodecane, which has data points up to 501.6 MPa).

This article reports a calibration procedure for the commercial Anton Paar DMA 512 densimeter usable at pressures up to 40 MPa. The method is based on water as a reference substance and requires knowledge of the characteristics of the cell as functions of temperature when subjected to a vacuum lower than 100 Pa. Comparis on with data from the literature indicates a relative accuracy of 0.1% where the classical calibration method (i.e. assuming no dependence of the densimeter performance upon pressure) led to a relative accuracy of 0.8% for the same substances.

New density data for diethyl adipate (DEA) over 12 isotherms [(293.15 e T e 403.15) K] and 15 isobars [(0.1 e p e 140) MPa] are reported. This paper presents also the calibration procedure we propose for a new experimental equipment. Data reliability has been verified over the pressure and temperature experimental intervals by comparing our experimental results for toluene and 1-butanol with previous literature data. A total of 732 experimental data points have been measured in the framework of this work. The experimental uncertainty is estimated to be ( 0.5 kg • m -3 (around 0.05 %). The pressure and temperature dependencies of diethyl adipate densities were accurately represented by the Tammann-Tait equation with standard deviations of 0.3 kg • m -3 . These data were used to analyze the isothermal compressibility and the isobaric thermal expansivity for this fluid.

A predictive scheme of viscosity for pure fluids and mixtures of simple molecules is presented. First, using molecular dynamics data from the literature and also from our own study, a representative correlation of the viscosity of a Lennard-Jones fluid is developed for a wide range of thermodynamic states. Second, a corresponding states scheme is proposed which allows the transposition of the previous results to real fluids. For some simple molecules, this scheme induces deviations lower than 5% in conditions covering gas, liquid, and supercritical states. For larger molecules, the results are poorer but can be strongly improved by fitting the atomic diameter. Then, it is shown for simple binary and multicomponent mixtures that, by using merely a van der Waals one-fluid approximation and the Lorentz-Berthelot rules, results are as good as for pure fluids. Finally, the limitations of such a scheme are shown when applied on the methane + toluene asymmetric mixture.