Interfacial tension of water near to critical conditions by using the pendant drop method: New experimental data and a correlation based on the parachor method

The interfacial tension (IFT) at vapor/liquid equilibrium was measured for the pure water system following the saturation line (further named as water (l)/water (v) or pure water) as well as for the binary water/nitrogen system (further named water/nitrogen). In order to obtain vapor/liquid IFT data, the pendant drop method was applied in a high-pressure-high temperature view cell. The vapor/liquid IFT of the binary water/nitrogen system was investigated at 10, 15 and 18 MPa and for temperatures in the range of 323-598 K. For the water (l)/water (v) system, the temperature ranges from 423 K to 623 K at the respective saturation pressure. The IFT of the binary water/nitrogen system is in a similar range compared to the IFT of the pure water system up to tem-peratures of 500 K although showing an influence of the nitrogen pressure due to solubility and adsorption effects. At temperatures above 500 K, the IFT starts to considerably differ as a function of temperature, reflecting the respective phase behaviour of both systems. The parachor method following Macleod-Sugden was used to correlate the IFT of the binary water/nitrogen system, as well as the pure water system. The equation is in good agreement with the experimental results, showing an AAD of 4.97% for the water/nitrogen system and 3.02% for the pure water system. The obtained experimental results are further in good agreement with comparable literature data.