Novel optical flow cell for measurements of fluid phase behaviour

We describe a novel optical flow cell for rapid automated isobaric measurements of liquid–liquid phase boundaries in binary mixtures. The apparatus was suitable for measurements at temperatures between 298 and 473 K at pressures of up to 7 MPa. The cell volume was only 35 μL but this was later increased to 55 μL to accommodate a magnetic stirrer. Measurement of a single point on the temperature–composition phase diagram could be accomplished within about 10 min. Results are reported for {(1 − x) H2O + x c-(CH2)4O} at pressures of 3 and 6 MPa.