Critical temperatures and critical pressures of four t he rmally unstable substances,including butyl acrylate, methyl methacrylate, allyl acetone and allyl alcohol,were measured for the first time via the quick- flow method. In the process,a small amount of sample was heated up to critical state in a very short time as it was passing through a capillary glass tube.The variation relationships of apparent critical properties with residence time wer e determined and the critical properties data were subsequently obtained by mean s of extrapolation. Polymerization reaction and other side reactions during the heating up process were minimized thanks to the short residence time less than 1 2 seconds.Therefore, this method is fit for measuring critical temperature and c ritical pressure of thermally unstable substance. The reliability of experimenta l apparatus was verified with 1-heptene as the standard substance whose accurat e critical properties can be referred to in literatures.
