COMPUTER-OPERATED DIFFERENTIAL STATIC APPARATUS FOR THE MEASUREMENT OF VAPOR-LIQUID-EQUILIBRIUM DATA

A computer-operated differential static apparatus is described, which is suitable for highly precise measurements up to appr. 100-degrees-C and 1 bar differential pressure. For the exploration of the very dilute regions, volume ratios of appr. 1:2000 of the components can be injected into the equilibrium cell with the required precision. The measurement of one isotherm with 60 data points requires 3 to 4 days and about 2-3 hours of human attendance. The main goal when setting up this instrument was to examine, if an automatic procedure would be reliable and safe enough for the determination of vapor-liquid equilibria by a static method. To prove this, a large number of measurements were performed over a period of appr. 11/2 years and minor modifications were made to improve operation. On the basis of these extensive tests, the range of operation may now be easily extended to higher temperatures and pressures. Besides a description of hardware design, experimental data sets will be shown. Special attention will be paid to the strongly diluted region.