METHODS TO PREDICT THE CRITICAL CONSTANTS OF ORGANIC-COMPOUNDS

New procedures are proposed to predict the critical values of temperat ure, pressure and volume of pure organic compounds. They require the n ormal boiling temperature, the orthobaric density at 20 degrees C and the molecular weight as input parameters. The critical temperatures ar e derived through simple relations linking T-rb to the above quantitie s while the critical pressures and volumes are evaluated by using the Rackett equation. Reliable results are obtained by evaluating the Rack ett constant, Z(ra), as function of T-b, sigma and M for several class es of compounds having similar properties. The proposed methods have b een applied to 144 organic compounds, both polar and non-polar. A comp arison is given with a literature method based on the group contributi on procedure.