Pressure and temperature dependence of the surface tension in the system natural gas/water principles of investigation and the first precise experimental data for pure methane/water at 25°C up to 46.8 MPa

Abstract

The surface tension in the system methane/water has been measured with the pendent drop method (rising bubble mode) at 25°C for pressures between 0.5 and 46.8 MPa. Precise data with a slightly pressure dependent absolute error of 0.3–0.4% are presented. Principles of the investigation, precision and execution of the experiments have been examined widely. Based on a profile parameter a simple correlation is presented which allows the estimation of the uncertainty of surface and interfacial tension data for any pendent drop/rising bubble profile. Comparison of the achieved data is done with the few published results available. The surface tension decreases for moderate pressures distinctly more with increasing pressure but reveals clearly higher values for higher pressures than previously known. The concentration of methane in the surface phase tends quickly to a saturation value as pressure is increased. A first interpretation of the achieved surface tension data shows that the surface concentration of methane is increased by nearly two orders of magnitude compared with the methane concentration in the aqueous volume phase, calculated from solubility.