Vapour pressures as a function of temperature for 1,3,5-trichlorobenzene [CA 108-70-3] (crystalline and liquid), 1,2,4,5-tetrachlorobenzene [CA 95-94-3] (crystalline), and 1,2,4,5-tetramethylbenzene [CA 95-93-2] (crystalline and liquid) were determined by means of a diaphragm manometer and simultaneous torsion, mass-loss effusion. An unconventional but simple method is used for the representation and the assessment of the present experimental results, together with results from other authors. The method is physical in nature, and at the same time reveals the quality of the experimental results in terms of random and systematic errors. The thermodynamic properties at p(o) = 1 Pa were evaluated, the results being (the uncertainties are standard deviations, and T-t denotes triple point): [graphics] (C)2001 Academic Press.