Rankine cycle is widely used in industry to convert heat to work using a working fluid. A mixture of oand m-isomers of dichlorobenzene can act efficiently as a working fluid in the cycle. An equation of state (EoS) approach was chosen to model vapor-liquid equilibria and phase properties in the system. The best results were achieved with Tsai-Chen EoS. Experimental measurements of volumetric properties of mixtures and solid-liquid equilibria were performed. These data were correctly predicted within the ideal assumption. An enthalpy-pressure diagram for the odichlorobenzene - m-dichlorobenzene system was calculated using the resulting EoS.