title: Method for locating the vapor-liquid critical point of multicomponent fluid mixtures using a shear mode piezoelectric sensor.
abstract: A new approach to locating the critical point of fluid mixtures is reported, utilizing a shear mode piezoelectric sensor. This technique employs a single piece of quartz crystal that is installed at the bottom of a strongly stirred high-pressure vessel. The sensor response indicates whether liquid or gas is in contact with its surfaces. Thus, the sensor is able to identify vapor-liquid phase separation by registering a discontinuity in the impedance minimum of the sensor as a function of pressure. Two systems (methanol + CO2 and H2 + CO2) have been investigated using this method. The critical point data of the methanol + CO2 system were chosen to validate the approach against a wealth of literature data, and good agreement was obtained. The sensor behavior in the two-phase region, as well as the effect of stirring, is discussed. The method is general and can be used with other sensors.
authors.affiliation: School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, U.K.
authors.forename: Jie
authors.initials: J
authors.lastname: Ke
authors.forename: P J
authors.initials: PJ
authors.lastname: King
authors.forename: Michael W
authors.initials: MW
authors.lastname: George
authors.forename: Martyn
authors.initials: M
authors.lastname: Poliakoff
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D017097:Electric Impedance; D044367:Phase Transition; D011791:Quartz; D012996:Solutions
chemical_list: D012996:Solutions; D011791:Quartz