The critical temperatures and the critical pressures of ferrocene, n-butylferrocene, benzoylferrocene, and 1-acetylferrocene have been measured. All the compounds studied begin to decompose at temperatures below their critical points. A method of pulse heating applicable to thermally unstable compounds has been used. Residence times were from (0.03 to 1.0)ms, which resulted in little decomposition of the substances in the course of measuring. The contributions of the groups Fe-CH and Fe-C for the estimation of the critical properties of ferrocene derivatives by the method of Marrero and Gani have been determined from the experimental data. (C) 2012 Elsevier B.V. All rights reserved.