The equilibrium pressure of ternary mixtures of {x(1)CH(3)F + x(2)HCl + x(3)N(2)O} covering the entire composition range has been measured at temperature of 182.33 K by the static method. The system exhibits a minimum pressure for the binary {x(1)CH(3)F + x(2)HCl}. The molar excess Gibbs free energy has been calculated from the experimental equilibrium pressure. For the equimolar mixture G(m)(E)(x(1) = x(2) = x(3) = 1/3) = (-297 +/- 20) J center dot mol(-1). The (p, x, y) surface for the ternary system and the corresponding curves for the three constituent binary mixtures obtained from the Peng-Robinson equation of state are in agreement with the experimental data. (c) 2006 Elsevier Ltd. All rights reserved.