Abstract
Weight loss and characterization of straight chain saturated fatty acids (even-numbered fatty acids : 8 kinds, odd-numbered fatty acids : 7 kinds) were studied by dynamic programmed thermogravimetry (TG), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC).1) Initial weight losses and weight loss curves of straight chain fatty acids under air and under nitrogen shifted only to the higher-temperature side with increase in carbon number. Weight loss patterns were simple and essentially the same to each other. The DSC curve of each fatty acid under air differed markedly from that under nitrogen. The curves of fatty acids under nitrogen shifted to the endothermic side. Under air, the DSC curves of fatty acids ranging from heptanoic to tridecanoic acids, also shifted to the endothermic side. However, the curves of fatty acids having carbon numbers exceeding that of tetradecanoic acid shifted to the exothermic side.2) GLC analysis of volatile and residual substances at the temperature corresponding to 25 % weight loss on TG indicated to the weight loss of fatty acid until to possibly be due primarily to evaporation of the fatty acid. However, the residual rate after the peak temperature of DTG increased with carbon number, this being particularly evident in the case of exposure to the air flow. Weight loss in the air flow is thus shown to be accompanied by decomposition.3) The peak temperature of DTG curve was closely correlated to fatty acid boiling point. However, the regression line in the air flow was situated on the lower-temperature side than that in the case of the nitrogen flow, due to accompanying decomposition.
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