alkanes against water have been measured over a range of temperatures, and the results discussed in terms of hydration of the hydrocarbon surfaces. The tension against temperature plots were in all cases linear, in contrast to the results for hexane given by Franks and Ives. The influence of electrolyte in the aqueous phase and of hydrocarbon homologues and isomers in the hydrocarbon phase on this linearity have been investigated. In the present temperature range, non-linearity may occur for some normal alkane mixtures but not others. This phenomenon seems to be related to discontinuities in the density against temperature curves for the hydrocarbons.