| Abstract
| - Wetting transition (Tw) andconsolute (CT) temperatures close to the upper critical solutiontemperature (UCST)have been determined for methanol + n-alkane mixtureswhere n = 6−12. Tw and theCT were also measuredfor noninteger n values, i.e., for mixtures of methanol +a binary mixture of two normal alkanes. The liquid−vapor surface tension (σLV) and the liquid−liquidinterfacial tension (σLL) were measured at 25 °C.For allmixtures studied the methanol rich-phase is denser than the alkanerich-phase. It is found that while the CTincreases continuously, the Tw first increasesand then decreases as a function of n. This is thefirst time that,for a homologous series of mixtures, this behavior has been found.For 6 ≤ n ≤ 8.25 the observed wettingtransition was from partial wetting to nonwetting (the alkanerich-phase intrudes between the methanol rich-phase and the vapor) while for 8.5 ≤ n ≤ 12 the transitionwas from partial to total wetting (the methanol-rich phase intrudes between the alkane rich-phase and the vapor).Both the change of Tw and theinversionin the nature of the wetting phase with n are in qualitativeagreement with the predictions of a recentlydeveloped mean-field model where a normalized parameter b,whose calculation involves σLV and σLL,playsthe role of n in the experiments.
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