The paper presents the results of measuring the critical temperatures and the critical pressures of normal alkanes : nonadecane, eicosane, docosane, tetracosane, hexacosane, octacosane, triacontane, hexatriacontane, and also naphthalene and m-terphenyl. The pulse-heating method of a wire probe immersed in the liquid under investigation applicable to thermally unstable substances has been used. Equations of state of a polymeric fluid of the van der Waals and Redlich-Kwong type have been written in a ＇self-consistent-fieId＇ approximation. Dependences of the critical constants of chain molecules on the number of links have been obtained. Equations for calculating the critical temperatures and pressures of normal alkanes have been derived. The results of calculations are compared with experimental data.