Work on the interrelations of the flammability properties of n-olkanes in air has been extended to both vapor and liquid fuel mixtures. By application of Raoult's and Dalton's laws governing vapor pressure and composition above a solution of two or more liquid hydrocarbons to Le Chatelier's rule governing the flammability limits of vapor mixtures, equations have been derived which make it possible to predict overall flammability properties of mixtures from the properties and proportions of the individual components. The properties which were studied include: lower and upper flammability limits, heat of combustion, stoichiometric concentration, flash point, and flammability index ("explosiveness"). Experimentally determined flash points of multicomponent solutions were in good agreement with the calculated values, confirming the point that hydrocarbon solutions follow the above laws, and also confirming the concept of flash point as that temperature at which the vapor concentration above a liquid is equal to that at its lower flammability limit. The derived equations demonstrate why vapor pressure of individual constituents plays a more important role than concentration on the overall flammability properties of liquid solutions, and that a very small amount of a highly volatile contaminant in a relatively nonflammable fuel may make it flammable.
Fungi and bacteria taken from fuel systems were allowed to grow in jet fuel (or hydrocarbon)–salt solution mixtures and the layers were analyzed for surfactant properties. The fuels included both JP‐4 and JP‐5 types and an alkylate bottom fraction. Controlled surface activity was imparted to some samples by adding minute quantities of either petroleum sulfonates or petroleum naphthenates. Analyses after growth periods of 2 to 14 weeks failed to show any significant increases in the surface active properties of any fuel or hydrocarbon sample. In all cases, there was either little change or else the surfactant effect was reduced slightly. Opposed to these findings, examination of the aqueous bottoms revealed that microbial growths did effect increases in their surface active properties.
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