Differential thermal analysis was used as a complementary method to “inverse” gas chromatography in the investigation of phase transition in mixed monolayers of hydrocarbon and alcohol deposited on a silica gel surface. It was found that in certain cases the DTA method provides more information about the behaviour of mixed monolayers than does gas chromatography. This is for monolayers with a low alcohol amount. Two endothermic peaks were produced as a result of disintegration of the hydrocarbon film. The presence of two mixed monolayer forms was found at alcohol concentrations greater than 65%.