A new apparatus has been constructed to measure vapor-liquid equilibria and saturated liquid densities of pure and mixed fluids. The density measurement is based on the buoyancy method using a single sinker and a magnetic suspension balance. The permanent magnet of the magnetic suspension balance carries the sinker with a load-coupling device. Both are completely submerged in the liquid phase. The electromagnet is placed outside the magnetically neutral cell walls. Both magnets transfer the buoyancy force of the sinker through the walls to a microbalance. The apparatus is limited to the temperature range from (-60 to 250) degrees C, pressures up to 200 bar, and densities in the range from (10 to 2000) kg center dot m(-3). Here, the first tests have been done with pure fluids at temperatures from (-40 to 90) degrees C and pressures up to 60 bar. Measurements of the compressed liquid density of water and gas density of nitrogen, carbon dioxide, and R134a confirm the accuracy of the density measurement. Also, measurements of the vapor pressure and the saturated liquid density were made for carbon dioxide and R134a. The estimated uncertainties of the experimental data are +/- 0.02 K for the temperature, +/- 5.0 mbar for the pressure, and +/- 0.013% + 0.01 kg center dot m(-3) for the density.