Single molecule thin films of various surface-active species are found on the surface of water bodies from the sea down to microscopic spray droplets. These films affect the properties of the water droplet and of the substance that makes up the film and have significant effects on atmospheric chemistry, meteorology, and, ultimately, climate change. Our work looks at films composed of mixtures of substances (e.g. oleic and stearic acid) and compares their behaviour to that of pure films. This experiment will study changes in orientation and phase behaviour of various relatively unreactive substances at the surface when a reactive substance present as part of a mixed film undergoes oxidation. NR is excellent for studying such systems, and we combine it with an innovative infra-red reflection system in order to study the phase behaviour of these mixed systems during oxidation in real time.