Critical wetting of a liquid/vapor interface by octane

The wetting of the planar interface between air saturated with octane vapor and an aqueous solution by octane is investigated by ellipsometry and inte rfacial tension measurements. The interfacial interactions are varied throu gh the concentration of the uncharged solute (glucose). We observe abrupt a nd continuous increases of the octane coverage with growing solute concentr ation. This we attribute to short- and long-range (dispersion) interactions , respectively. The continuous thickness growth is analyzed as a critical w etting transition.