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