Differential Thermal Analysis under High Pressures II: Investigation of the Rotational Transition of Several n‐Alkanes

Abstract

AbstractA DTA apparatus is applied to the calorimetric investigation of the phase behaviour (especially the rotational transition) of 13 n‐alkanes containing 9, 11, 12, 13, 15, 17, 18, 19, 21, 24, 25, 27, and 31 carbon atoms as well as the binary system nonadecane/heneicosane up to 3000 bar. The pressure transmitting gas has to be prevented from being dissolved in the substances, otherwise the phase behaviour will be completely changed.The calorimetric measurements allow a rough calculation of the latent heats and the volume changes involved with the phase transition. From these data the conclusion may be drawn that the specific volume of the n‐alkanes just below the rotational transition temperature as well as the volume change according to the rotational transition are obviously independent of pressure and chain length apart from a certain odd‐even‐effect.