Fully automated workstation for liquid - Liquid equilibrium measurements

A fully automated workstation has been developed and applied to the measurement of liquid-liquid equilibrium. The measurements, starting from solution preparations through equilibrium establishment and chemical analysis of both phases and ending with the determined solute concentration in both phases, can be done on a 24 h per day basis with no human intervention at all. To evaluate the accuracy of the measurements, the equilibrium distribution ratios of acetone between toluene and water at 20 degreesC and of caprolactam between toluene and water at 40 degreesC and between benzene and water at 20 degreesC are measured and the results are compared with the values reported in the literature and, for the caprolactam systems, also with those obtained in a jacketed equilibrium cell. Furthermore, the distribution ratio of caprolactam between toluene and water has been measured several times for the same initial caprolactam mass fraction in order to evaluate the repeatability. The obtained results are in very good agreement with the literature values for the acetone system and with those measured in the glass cell for the caprolactam systems, while a coefficient of variation of 1.8% for a seven times repeated measurement was found.