The liquid phase equilibrium reaction of dihalomethanes (2CH(2)BrI reversible arrow CH2Br2 + CH2I2) has been investigated by NMR spectroscopy, as a function of the temperature and initial concentration of the reactants. The equilibrium constants have been experimentally determined for this reaction from the profile of the NMR spectra. Heat capacity measurements were carried out in the temperature range from 293.15 to 353.15 K by differential scanning calorimetry. The results relate the heats of formation of the three compounds and confirm the recently determined heat of formation of CH2I2 of 107.5 kJ mol(-1). (c) 2005 Elsevier B.V. All rights reserved.