MEASUREMENT OF THE CRITICAL PROPERTIES OF THERMALLY UNSTABLE SUBSTANCES AND MIXTURES BY THE PULSE-HEATING METHOD

A method of measuring the critical temperatures and pressures of thermally unstable substances has been developed. The method is based on measuring the temperature of the attainable superheat with the help of a thin wire probe heated with electric-current pulses. With increasing pressure the temperature of the attainable superheat tends to the critical temperature. The authors have obtained a formula by which the dependence of the apparent critical temperature on the heating time is extrapolated to the critical temperature of an undecomposed substance. The results of measurement of the critical temperature and pressure of ethene glycol (ethane-1,2-diol), glycerin (propane-1,2,3-triol), dicumylmethane (di-1-methylethyldiphenylmethane), and (hexadecane + carbon dioxide) are given. © 1993 Academic Press Ltd.