Realisation d'un ensemble destine a la mesure de faibles pressions de vapeur (Domaine: 3–1000 Pa)

Abstract

Equipment is described for measurement of low vapor pressure, P 0, in the range: 3 Pa < P 0 <1000 Pa; 50°C < t < 250°C. A possible error of 1% in P and ± 0.02°C in T were estimated. The inert gas-saturation method was used. The vapor pressure was determined by measuring the saturated vapor concentration in the inert gas using a gas chromatograph. The detector chromatograph was calibrated for the material studied. External calibration was chosen and a special syringe was designed and built for this purpose. The apparatus was designed with the following features: (1) by adapting a sample injection valve the gas phase analysis is simple and very accurate; (2) the use of a differential pressure transducer permits accurate measurement of inert gas pressure. The partial vapor pressure, P i, was measured for several total pressures, P. The extrapolation to P = 0 of the plot log P i, vs. P gave the partial vapor pressure of pure substance. This method was derived from thermodynamic considerations (Poynting effect and non-ideality of gas phase).