The Tait equation has been extended and generalized to permit the calculation of densities of compressed liquids and their mixtures to a pressure of 68,950 kPa (l0,ooO psia) using only critical temperature, critical pressure, Soave-Redlich-Kwong acentric factor, saturation pressure, and saturated volume for a pure liquid or the corresponding mixture parameters for a liquid mixture. This correlation, together with the correlation developed by Hankinson and Thomson (1979) (1965,1969). In order to achieve acceptable accuracy, the Yen-Woods (1966) correlation requires specific parameters for each compound. The Tait (1888) and Hudleston (1937) equations also lack mixing rules and have generally been used to fit and smooth experimental data.In this work the Tait equation was extended and its parameters were generalized as functions of an acentric factor derived from the Soave-Redlich-Kwong equation of state, critical temperature, and critical pressure. The saturated density and saturation pressure of the liquid which are used in the Tait equation were calculated using the saturated liquid density correlation developed by Hankinson and Thomson (1979) and a generalized vapor pressure equation. The two density correlations together comprise COSTALD, a unified method of estimating saturated and compressed densities of pure liquids and liquid mixtures. CONCLUSIONS AND SIGNIFICANCEThe Tait (1888) equation has been extended to permit accurate prediction of compressed densities of a wide variety of liquids and mixtures for temperatures in the general range of 50 to 600 K and pressures from saturation to 68,950 kPa (l0,ooO psia) using only critical temperature, critical pressure, SRK acentric factor, saturated volume, and saturation pressure for a pure liquid or the corresponding parameters for a mixture.A universal temperature dependence for all nonpolar and slightly polar liquids and mixtures was determined for the constant B in the Tait equation. Both Tait equation constants, B and C , were generalized as functions of the SRK acentric factor. Densities calculated using the extended Tait equation in conjunction with a saturated liquid density equation, COS-TALD (Corresponding STAtes Liquid Density), recently developed by Hankinson and Thomson (1979), were compared with those calculated using the Yen-Woods (1966) method. The data base used for testing consisted of 6,338 density points for pure, nonpolar liquids, 1,352 points for polar and quantum liquids, and 6,926 mixture density points including 319 points for LNG/LPG mixtures.The COSTALD correlation is shown to be the most general and most accurate compressed liquid density correlation yet published. Average absolute errors in densities calculated using COSTALD were 0.446% and 2.57% for pure nonpolar and polar liquids respectively compared to 1.49% and 3.48% errors obtained with the Yen-Woods method. COSTALD gave 0.369% and 1.61% average absolute errors for LNG/LPG mixtures and for all mixtures compared to 1.46% and 2.51% for the YenWoods method.The two parts of the COST...