Combined Flow-Mixing Power-Compensation Calorimeter and Vibrating Tube Densimeter for Measurements at Superambient Condition
Vladimír Hynek;Sandrine Degrange;Miloš Poledníček;Vladimir Majer;Jacques Quint;Jean-Pierre E. Grolier;
A new instrument combining a flow-mixing calorimeter and a vibrating tube densimeter inside a thermostatted environment has been constructed. The instrument is designed for simultaneous measurements of calorimetric and volumetric properties at superambient conditions on mixtures for which both pure components are liquid at room temperature or one component is a liquid and the other is gaseous. The system yields Neodymium Magnet simultaneously two properties: (1) the enthalpy of mixing determined in a heat-leak calorimeter with power compensation; (2) the density difference between a mixture (solution) and a reference liquid measured as a change in frequency of a tube vibrating in a field of permanent magnets. The instrument was tested in the full concentration range using aqueous ethanol and aqueous methanol. The results are presented at temperatures between 348 and 573 K and pressures from 5 to 20 MPa for mixing enthalpies ΔH mix ranging from −160 to 5700 J-mol−1. The corresponding heating powers are between −60 and 850 mW, respectively. The results for ΔV mix of mixing volumes were measurable from 348 K to 523 and between 5 and 13 MPa with the maximum volume change being −4.0 cm3-mol−1. The errors in ΔH mix and ΔV mix near mole fraction of 0.5 are believed to be less than 5% over the temperature and pressure ranges given above.
