What is the correct interfacial tension between methane and water at high-pressure/high-temperature conditions?

The purpose of this communication is to draw attention to a puzzling inconsistency in the published data for the interfacial tension between methane and water at high-pressure and high-temperature conditions. The published data sets fall into two categories – those exhibiting linear dependence of interfacial tension on temperature, in agreement with the phenomenological Eötvös rule, and others exhibiting a peculiar and seemingly reproducible non-linear trend. The inconsistency seems to have gone largely unnoticed. That is somewhat disconcerting considering that the methane/water system is a commonly used reference system for evaluation of fluid interfacial tension models. The literature data are reviewed, discussed, and compared with a novel set of interfacial tension data for the methane/water system obtained in this study.