“…In order to simplify the situation at the interface we concentrate here on ionic surfactants the solubility of which in alkanes is extremely low and therefore negligible. One of the very systematically studied homologous series of ionic surfactants is the cationic alkyltrimethylammonium bromide C n TAB, which was intensively investigated at different interfaces in various ways, for example the adsorption dynamics, [24][25][26][27][28] the adsorption isotherms at water/air 16,[29][30][31] or water/alkane interfaces 17,32,33 by tensiometry but also by neutron reection. [34][35][36][37]39 The number of data on alkane co-adsorption at the interface between an aqueous surfactant solution and alkane vapor is rather small, however, there are some rst studies in which also the cationic surfactants C n TAB are investigated (see ref.…”