Evaluation of the force constants of non-polar gases from viscosity data

The analytical expressions for the transport coefficients (i.e. viscosity, thermal conductivity, and diffusivity) of an ideal gas can be derived from the kinetic theory of gases. It is also possible to make these analytical expressions adequate for real gases if the intermolecular forces of attraction and repulsion for these gases have been taken into consideration. The intermolecular forces have been studied by many investigators. The Lennard-Jones potential is one of the most realistic semi-empirical statements which represents particularly the intermolecular forces of attraction and repulsion for non-polar gases. The values of the Lennard-Jones potential parameters or the force constants of the non-polar gases have been determined from both diffusion and viscosity data. The work of previous investigators have indicated that the values of the force constants determined from diffusion measurements were not always in good agreement with those obtained from viscosity data. Much of the viscosity data of gases available from the literature have been measured under flow or dynamic conditions. The purpose of this research was not only to determine the actual viscosities of a few non-polar gases at three temperature levels by means of a rolling viscometer, but also to demonstrate that this method was accurate enough to determine the Lennard-Jones force constants for the gases used. In addition, the calculated force constants were to be used to determine viscosities, self-diffusion coefficients of single gases and diffusivities of binary pairs at various other temperatures and compared with actual experimental data and literature values. If the above could be accomplished satisfactorily, the work could be extended to determine the force constants, viscosities, and diffusivities of non-polar gaseous mixtures. The gases used in this investigation, in addition to air, which was used to calibrate the viscometer, were argon, helium, carbon dioxide, oxygen, nitrogen and hydrogen --Introduction, pages 1-2