A computer operated apparatus for the measurement of liquid densities of pure compounds and mixtures in a large temperature and pressure range was developed in 1997. A high pressure/high temperature vibrating tube densimeter (DMA-HPT prototype from Labor für Meßtechnik Stabinger (Graz, Austria)) is used for the measurement of the density in a wide temperature range.

The measuring cell contains an U-tube oscillator (Hastelloy C-276), a thermostat, temperature sensors for control and measurement as well as excitation and measurement coils using permanent magnets. A modified DMA control unit is attached to the measurement cell. The pressure is adjusted with the help of a variable volume (Ruska) connected to a stepping motor. For pressure measurement a sensor (Druck) is attached to the variable volume.

The measurement is controlled with the help of the Windows program "Densitas per Motum – Density Measurement". Automatic temperature and pressure programs for the liquid density measurements of compressed pure compounds and mixtures up to 523 K and 40 MPa are possible. The control program is connected to the pure component data bank of the Dortmund Data Bank (DDB-PCP). By using the Antoine equation (parameters from the DDB-PCP) each isotherm is started slightly above the saturation pressure.

The following figure shows a schematic drawing of the complete setup:

Results of typical measurements are shown in the next figures:

The main window of the control program contains all important input and the current status of the measurement:

We thank Labor für Meßtechnik Stabinger (Graz, Austia) for supplying their DMA-HPT prototype vibrating tube densimeter for our research.