UNIQUAC: Group Contribution Method for Evaluation of Activity Coefficients

The acronym UNIQUAC stands for Universal Quasi Chemical Equation. The principle that the UNIQUAC method is founded on is that of group contribution. The methodology is based on the postulate that any thermo-physical property of a pure substance is a weighted sum of the chemical groups that constitute it. Since the number of functional groups (such as are few (about 50 or so) in comparison to the vast number of chemical species they can form, the approach based on group contribution constitutes an universal, and indeed a versatile method of prediction of a wide variety of properties of a very large number of substances. Properties as diverse as normal boiling point, enthalpy of vapourization, molar volume, thermal conductivity, viscosity, surface tension, etc may be estimated when no direct experimental data are available.