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Monomolecular films of fatty acids on water solutions have been studied extensively and have been found to show properties related to the molecular structure of the fatty acids (1). The force-area curves of monolayers indicate the apparent cross-sectional area of the molecules in the film, and their shapes differ one from the other dependent upon intermolecular forces, which in turn are an expression of the molecular structure. Studies of monolayers of some unsaturated fatty acids have been made (1, 3, 9, 16), but a systematic comparison of the monolayers of isomers of unsaturated fatty acids, including conjugated and nonconjugated polyunsaturated acids, has hitherto not been carried oui. Such a study of isomers of unsaturated acids could conceivably give more information as to the effects of isomerism upon the packing of molecules in a monolayer and, conversely, could perhaps offer evidence regarding the structure of tarty acids whose structure is not definitely known.Inasmuch as a group of oxy fatty acids were available for study, it .-eemed also of interest, as a basis for the study of the oxidation of unsaturated fatty acids in monolayers, that the force-area curves of these be investigated. Some of these substances also afford further opportunity for the study of the effect of isomerism upon monolayer characteristics. EXPERIMENTAL Monolayers were spread on Ay 100 sulfuric acid containing 0.12 per cent hydroquinone in a Langmuir hydrophil balance supplied by the Central Scientific Company. The films were spread from dilute solutions of the fatty acids in redistilled petroleum ether (b.p. 45°C.) except in the cases of /3-licanic acid, diketostearic acid, and rieinelaidic acid, for which redistilled c.p. thiophene-free benzene was used as solvent. The solutions were expelled onto the water surface from a calibrated 0.5-ml. syringe having a stationary back-stop. All experiments were run at room temperature, and with each substance tested, a sample of stearic acid was run as a standard. The limiting areas were corrected assuming that• of stearic acid to be 24.4 A.', as found by Nutting and Harkins (201 -The experimental data are taken from a thesis submitted to the Graduate School of the University of Minnesota by V. Lorraine Schneider in partial fulfillment of the requirements for the degree of Master of Science in 1946.

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