Riedel equation calculate vapor pressure as follow,

Tc : Critical Temperature Pc : Critical Pressure Tbr : boiling Point / Critical Temperature Tr = measure Temperature / Critical Temperature

Please draw molecule at cyan panel. Please refer to how to use animation1, animation2.
Change atom type or delete atom, mouse down and up at the same atom. You will see the several buttons and select one. Web version can not calculate Halogen and Aromatics.

Cis-, Trans- compounds return average of both.
You need not add Hydrogen.

If you are lucky enough your browser support old JAVA and proper setting of JAVA option, you will see the window like below.

If you can not see this window, please check browser's JAVA option or try other browser. Eventhough you fail. Give up this old IAVA verson. (This Applet is still running with Mac with FireFox browser. 2011.11.15)