Method for determining the density of fluid media

The actual density of liquids is determined with a flexural oscillator that is excited at two different natural vibrations. The presence of air/gas inclusions or other inhomogeneities in a liquid is detected and their influence can be eliminated. In an initial step, the periods of the inherent vibrations and of at least one vibration damping value of the natural vibrations are determined for liquids having different densities and viscosities. Liquid densities as well as the difference between them and between the vibration damping values are determined from this. An inclusion-free curve (KB) which reflects the functional dependence F( δ) between the relative density differences and the vibration damping differences is calculated and the exact function determined; i.e. the gas/air inclusion-free curve (KB) is expanded by introducing a deviation bandwidth (ab) to form an inclusion-free curve area (KF), which is stored. The functional value F( δ) of the liquid to be tested is determined and a check is performed to ascertain whether it is within the inclusion-free curve area and whether the resulting value of the density is or is not applicable to the liquid being tested.