2. Gas at atmospheric pressure

In general, there are very few measurements of the viscosity of gases at atmospheric pressure, compared with that of liquids under the same experimental conditions. This is probably due to the experimental difficulties involved. On the other hand, for the most common compounds (around a hundred), there is a wealth of experimental data extending over a wide temperature range. The accuracy of these data often varies from one author to another. Some authors estimate viscosity measurement accuracies of the order of 0.5%, and even less than 0.5%. However, the discrepancies observed between experimental viscosity values for a given compound are often much greater than 0.5%.

Gas viscosity can also be calculated from gas kinetic theory using intermolecular potential parameters. Some authors believe that values obtained in this way are sometimes more accurate than experimental...