(756a) Pulse-Heating Method for Measuring the Critical Temperatures and Pressures of Thermally Unstable Compounds

The pulse-heating method for the measurement of the critical temperatures and pressures of thermally unstable compounds has been presented. The method is based on the measuring the temperature of the attainable superheat of a liquid. With increasing pressure, the temperature of the attainable superheat tends to the critical temperature. The temperature of the attainable superheat is measured with the help of a wire probe heated by electric current pulses, 0.01-1.0 ms in length. The short residence times provide little decomposition of compounds in the course of the experiments. The uncertainties of the critical properties measured are as follows: , (is the absolute temperature) for â??usualâ? low-molar-mass compounds and , for compounds with hydrogen bonding or with high acentric factor (). The results of the measurements of the critical properties of about 200 compounds have been discussed.