This paper documents the construction details and experimental procedures for the continuously weighed pycnometer used in our laboratory to measure fluid properties such as densities, saturation pressures, phase boundaries, and isothermal compressibilities. This apparatus consists of a cell suspended from an electronic balance at all times and a variable volume bellows cell which is used to adjust the confined sample density within an isothermal enclosure. The principal advantages of this apparatus are rapid measurement and relatively high accuracy. Some experimental results are presented to illustrate capability. The accessible experimental ranges are 100−450 K up to 200 MPa; measurement accuracy is 0.1% or better.

efficient method for obtaining sorption equilibria for systems with up to two vapor phase components at finite concentration. The objective of this work was to obtain a theoretical result that could be used for experimeptal determinations of sorption of multiple interfering species at finite concentration. Results obtained are applicable for both non-stoichiometric and stoichiometric situations for systems that may have flowing phase velocity and volume changes associated with interphase transport and also may have interactions among the sorbed components. The dependence of each effluent peak characteristic velocity upon all of the component equilibrium isotherms requires that the equilibria be considered as a whole by simultaneously fitting a set of composition grid perturbation response data to appropriate isotherm surface equations.

This work brings together recent gas chromatography experiments and theory involving multiple sorbing species at finite concentration, and theories for multicomponent polymer solutions by means of the parameter estimation procedure of Part 1. Results quantitatively describe the wide variation in peak retention times that are caused by phase equilibrium and chromatographic interference, the best solution models doing so to within or near experimental error. The chromatographic method is capable of detecting differences and peculiarities in the various polymer solution models in both the accuracy of the calculated retention times and the sensitivities of the calculations to the model parameters. Perturbation chromatography offers some unique capabilities for multicomponent vapor-liquid equilibrium determinations.

SynopsisA perturbation chromatography apparatus has been designed and constructed for determining the vapor-liquid equilibrium between a two-component (solvent/helium) vapor phase and a twocomponent (polymer/solvent) liquid phase. The apparatus performed very well, giving reproducible and reliable results that agree with independent, previously reported studies. All tests of the equipment indicated that it was successful in meeting the conditions of low column pressure drop, small perturbations, and slow flow rate that are required for perturbation chromatography. Binary polymedsolvent data were obtained for polybutadiene (PBD)/benzene or polybutadiene/cyclohexane systems at solvent partial pressures to 40 kPa and for n-hexane a t infinite dilution, all a t the three temperatures of 333.15,355.00, and 373.15 K. The experimental data for each system can be represented within experimental error by the Flory-Huggins polymer solution theory using a single binary interaction parameter that is independent of temperature and concentration.