Reactions of stearic acid with the contacting surfaces presented by underlying copper and aluminum metals as balance pans and fine powders have been examined by thermal measurements of mass and enthalpy changes in air and in argon. These data have been interpreted to include dehydrogenation, decarboxylation, and dehydration steps with supporting evidence gathered from evolved gas analysis by gas chromatography and from solid structural analysis by X-ray diffraction, electron diffraction, Fourier transform infrared spectroscopy, and electron microscopy. Although no metal soaps were detected in aluminum/stearic acid reactions, it seems likely that a copper stearate complex was formed in air at 200 °C. The material absorbed at 1590 cm"1 but did not exhibit a stable crystalline configuration in diffraction experiments.

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The effect of heat on the decomposition of two grades of soybean lecithin has been examined up to 600°C using differential scanning calorimetry and thermogravimetry. Studies were carried out in both air and argon and a kinetic analysis of the isothermal rates of reaction was attempted. Three principal decomposition stages were distinguished in argon and four in air for a water-dispersible lecithin typical of the quality of the material used in many industrial applications. Gas chromatography showed that the principal gases evolved from 50 to 600°C in argon from the water-dispersible lecithin in contact with aluminum surfaces were C, -C6 hydrocarbons, carbon dioxide, carbon monoxide, water and traces of hydrogen. L'effet de la temperature sur la decomposition de deux categories de lkcithine provenant de la graine de soja a ett examine jusqu'a 600°C I'aide de la calorimCtrie diffkrentielle a balayage et de la thermogravimetrie. Les etudes ont ttt effectuees en presence d'air et d'argon, et une analyse de la cinetique des reactions isothermes a Cte tentee. Trois principales Ctapes de decomposition ont etC distinguees sous atmosphere d'argon et quatre lorsque l'air est employe, et ce, a partir d'une lecithine dispersable dans l'eau ayant une qualit6 typique de ce qui est utilisC dans plusieurs applications industrielles. Des analyses par chromatographie en phase gazeuse ont dCmontrC que les principaux gaz form&, lorsque la lecithine en contact avec de l'alurninium est chauffke a des tempkratures de 50 a 600°C en presence d'argon, sont des hydrocarbures de type C, a Cbr du monoxyde et bioxyde de carbone, de l'eau et des traces d'hydrogbne.he industrial uses, properties and compositions of leci-

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