Composition Dependence of the Liquid/Air Interfacial Tension of 2‐Butoxyethanol/Water Mixtures at Temperatures below the Lower Critical Temperature

Measurements of the liquid/air interfacial tension σα,βγ (α, vapour phase; (βγ), homogeneous liquid phase) of 2‐butoxyethanol (abbreviated C4E1)/water mixtures carried out as function of temperature (15°C≤T≤50°C) and composition (O≤x≤1; x, mole fraction of 2‐butoxyethanol) reveal the existence of extrema in the σα,βγ versus x curves measured at constant temperature. The location of the minimum on the composition axis xmin approaches the critical composition xc when temperature approaches the critical temperature Tc. For composition xc xc. This could reflect the existence of a wetting transition from partial wetting of the α,γ interface by water‐rich phase γ to complete wetting of this interface by phase γ at a temperature very close to Tc. The existence of such a transition was presumed in the literature.