  A simple fast algorithm of the conodes calculation in binary systems is
proposed. The method is based on exact solution of the problem on common
tangent to pair of approximating parabolas. Sequence of approximating parabolas
pairs having second order tangency points on separated concave parts of free
energy isotherm is generated. The sequences of the tangency points pairs
conodes with approximating parabolas converge to equilibrium compositions of
phases in binary systems.
  PACS: 64.75.-g; 64.10.+h; 05.70.Ce; 82.60.-s
  Key words: Phase equilibria; Free energy; Binary systems; Conode; Phase
diagrams.
