6. Chemical nature of steam above an ionic liquid

The chemical nature of the vapour above an ionic liquid is an important question in interpreting hypergolic ignition, if we assume that self-ignition results from the reactivity of vapours from the ionic liquid with those from the oxidizing agent. We therefore need to find out how vapour pressure arises from an ionic liquid, a question that makes no sense with a molecular liquid. In the latter case, unless the liquid is subjected to a high temperature, the molecule in the gas phase is the same, from the bonding point of view, as in the liquid phase. In the case of ionic liquids, the question cannot be answered so quickly, as four possibilities exist. At equilibrium above the liquid phase, a pair of ions, or separate ions, or a neutral pair or separate neutral species could exist. Experimental results and theoretical calculations are reported in the literature on this question. It seems that...