Special equipment has been designed and constructed to measure pressure-volume-temperature (PVT) data through the vibrating tube method. At constant temperature, pressure is increased by steps using a pressurizing cell. For each stabilized pressure value, the vibrating frequency of the tube is recorded and translated into density through calibration with known density samples. Experimental PVT measurements on several pure compounds and mixtures have been carried out. Data reliability has been verified by comparisons with literature data available for methane-, ethylene-, methanol-, propane-, 4-methyl-1-pentene-, and n-heptane-methylcyclopentane binary mixtures for temperatures between 298 and 398 K and pressures between 2.5 and 39.5 MPa. New data are given for binary and ternary liquid mixtures of the carbon dioxide-methanol-propane system at four temperatures, 323, 348, 373, and 398 K, between 2.5 and 39.5 MPa.