Viscosities available in the literature for the gaseous and liquid states of eleven substances have been correlated with reduced density by the use of dimensional analysis and the Abas-rade expression for the residual viscosity to produce a single generalized relationship which is presented both graphically and analytically. The substances are argon, nitrogen, oxygen, carbon dioxide, sulfur dioxide, methane, ethane, propane, i-butane, n-butane, and n-pentane. The properties required for the calculation of viscosity with this relationship are the molecular weight, the critical constants, and the density of the substance a t the temperature and pressure considered.Separate relationships were developed for hydrogen, ammonia, and water which do not follow the consistent behavior of the other substances. Viscosity values for ethylene calculated with the generalized relationship compared favorably with the corresponding experimental values.In 1944 Uyehara and Watson developed a generalized correlation for the prediction of the viscosity of a pure substance at any temperature and pressure ( 7 9 ) . Although this correlation has proved to be of extreme utility for industrial calculations, current demands for highly accurate viscosity values in such areas as heat transfer and reactor design necessitate the development of a more exacting method for obtaining viscosities of both gases and liquids.Recent studies on the prediction of the transport properties of pure substances have been primarily concerned with the viscosity and thermal conductivity of gases at normal pressures (47, 74, 7 5 ) . Using a dimensional analysis approach and viscosity data reported in the literature for fifty-two nonpolar and fifty-three polar gases, Stiel and Thodos (74, 7 5 ) have developed relationships which can easily be applied for the prediction of the viscosity of any pure gas at moderate pressures (0.1 to 5 atm.). For nonpolar gases the following relationships resulted: (2), (3), and (4) for all the substances investigated were found to compare favorably with the corresponding experimental values. Therefore it would be desirable to utilize a similar approach to develop relationships for the prediction of the viscosity of pure substances at high pressures in both the gaseous and liquid states.In 1952 Abas-zade (1) proposed that the following relationship exists between the residual thermal conductivity of a liquid and its corresponding density:Thodos and co-workers (23, 33, 50, 66, 68) have studied the transport properties of several individual substances over a complete range of temperatures and pressures and have found that Equation (5) and a similar expression for the residual viscosity
