International Journal of Thermophysics, Vol. 19, No.6, 1998 Surface Tension of Pure Hydrocarbons 1 A. Romero-Martinez 2 and A. Trejo2. 3 A new correlation scheme for the surface tension of a homologous series of pure liquid hydrocarbons, as a function of molecular weight and temperature, is presented. Using orthobarie surface tension data from literature for four homologous series of hydrocarbons, i.e., n-alkanes, I-alkenes, cycloalkanes, and aromatics, the adjustable parameters for two new surface tension equations are obtained individualty for each series. The agreement between experimental values and those calculated with the two new generalized surface tension equa- tions is very good, i. e., the temperature and molecular weight dependences of surface tension are welt reproduced. KEY WORDS: alkanes; alkenes; aromatics; correlation equations; cyclo- alkanes; hydrocarbons; molecular weight; surface tension; temperature. 1. INTRODUCTION Surface tension of pure and mixed liquids is an important thermophysical property for almost every separation process involving mass transfer between vapor and liquid phases. For both the refinery and petrochemical needs of the oil industry, thermophysical and phase equilibria properties of hydrocarbons are of the utmost importance for the design, operation and optimization of chemical and separation processes. Also, the surface tension has been part of the systematic analysis carried out to understand the asymptotic behavior of different 'physical properties. Nonetheless, an examination of the literature shows that experimental data of surface ten- sion over a large temperature range are lacking even for pure components. I Paper presented at the Thirteenth Symposium on Thermophysical Properties, June 22-27, 1997, Boulder, Colorado, U.SA lInstituto Mexicano del Petroleo, Subdireccion de Transformacion Industrial, Gerencia de Investigacion Aplicada de Procesos, Eje Lazaro Cardenas 152,07730 Mexico, D.F., Mexico. 3 To whom correspondence should be addressed. 1605 019S-928X/98/1I00-160SS15.00jO <01998 Plenum Publishing Corporation