LAUSR

The present paper describes a numerical technique to compute phase equilibria of ternary liquid systems. First, particle swarm optimization is used to estimate the binary interaction parameters of the NRTL (Non‐Random Two Liquid) and UNIQUAC (Universal Quasi‐Chemical) models. We show how the arc‐length continuation method allows the calculation of the liquid–liquid equilibrium diagram for any ternary system. A total of seven case studies of industrially important mixtures are described. Both Type I systems (oleic acid–water–ethanol, water–1‐propanol–toluene, DEC–ethanol–water, water–propionic acid–n‐hexane, and water–TMA–benzene) and Type II mixtures (water–1‐butanol–n‐hexane) are discussed. In addition, a system with temperature‐dependent behavior (n‐hexane–methyl cyclopentane–aniline) is studied. The numerical techniques and the thermodynamic problem involved in this paper are suitable for a first‐year graduate‐level course in chemical engineering. All computer coding is based either on Mathematica© or Matlab®. This is an ideal opportunity to introduce graduate students to advanced commands and programming syntax of state‐of‐the‐art mathematical software.