Abstract: A density measuring apparatus (densitometer) useful for rapid absolute determination of the density, the temperature dependence of density, partial volume and thermal expansivity of condensed matter, based on the hydrostatic method, employs an electronic balance enclosed in an airtight envelope which forms a weighing chamber and a measuring chamber. The balance comprises a balance beam and measuring and weighing hangdown assemblies attached to opposite ends of the beam. The balance beam and the weighing hangdown assembly are positioned in the weighing chamber. The measuring hangdown assembly extends from the weighing chamber into the measuring chamber and comprises a thin suspension wire and a sample support or a sinker which are positioned in a multi-jacket measuring vessel adapted to receive a buoyant or sample liquid. A vapor barrier is provided between the weighing and measuring chambers to prevent vapors of the buoyant or sample liquid from flowing into the weighing chamber.