This work entails the design and development of a static variable-volume cell with the aim to measure high-pressure phase equilibria of mixtures of supercritical solvents and paraffinic hydrocarbons. The cell was used to measure the ethane-n-alkane phase equilibria and densities near the critical point of the mixture. Experimentally determined phase equilibria are reported for the binary mixtures of supercritical ethane with n-C-16, n-C-24 and n-C-28 in the temperature range of 313-352 K. Several equations of state (EOS) were fitted to this data, and it was found that the Soave-Redlich-Kwong equation gives a reasonable representation of the measured phase equilibria but fails in the representation of the mixture densities-a known problem of cubic EOS. The use of the Patel-Teja EOS resulted in the smallest error in the liquid phase density representation. (C) 2001 Elsevier Science B.V. All rights reserved.