Two methods, a Soave-Redlich-Kwong cubic equation of state (SRK CEOS) and a two-fluid corresponding states procedure, models A and B respectively, have been used to predict the three phase equilibrium compositions, pressures and liquid molar volumes for binary ethane + nitrogen and the three phase equilibrium compositions and liquid molar volumes for ternary methane + ethane + nitrogen mixtures. Each method uses its own phase equilibrium algorithm which incorporates robust stability analysis procedures. Comparisons of the predictions with experiment show that both models give good agreement with the data.