In comparison with the liquid/air interface, interactions of surfactants at the liquid/oil vapor interface are poorly understood due to the lack of experimental data available. We have recently worked on several aspects of the interactions including the use of different alkanes and partial pressures in the vapor phase as well as various surfactants at different concentrations in the aqueous phase. These data have allowed us to develop thermodynamic models for molecular interactions in mixed monolayers, but the interfacial composition has, to date, not been experimentally verified. A recent test experiment on Figaro demonstrated that we can successfully measure with high precision the kinetics and equilibrium values of the surface composition of hexane and different surfactants in the mixed monolayers. Following this validation of our approach, we propose an extensive set of optimized neutron reflectivity measurements on the full range of surfactants and concentrations already studied in our labs. With the experimental data obtained, we will be able to verify and further refine the thermodynamic and kinetic models that form the current basis of our understanding of this subject.