Apparatus to measure vapor pressure, differential vapor pressure liquid molar volume, and compressibility of liquids and solutions to the critical point. Vapor pressures, molar volumes and compressibilities of benzene and perdeuterated benzene at elevated temperatures

Abstract

An apparatus designed to measure vapor pressure differences between two similar liquids, such as isotopic isomers, or between a solution and its reference solvent at temperatures and pressures extending to the critical point is described. Vapor-phase volume is minimized and pressure is transmitted to the transducer through the liquid, thereby avoiding several experimental difficulties. Liquid can be injected into the heated part of the system by volumetrically calibrated screw injectors, thus permitting measurements of liquid molar volume, compressibility, and expansivity. The addition of a high-pressure circulating pump and injection valve allows the apparatus to be employed as a continuous dilution differential vapor pressure apparatus for determining partial molar free energies of solution. In the second part of the paper data on the vapor pressure, molar volume, compressibility, and expansivity and their isotope effects for C/sub 6/H/sub 6/ and C/sub 6/D/sub 6/ from room temperature to near the critical temperature are reported.