[1][2] Such a solution is formed by random mixing of components of similar molar volume and without strong specific interactions,[1][2] and its behavior diverges from that of an ideal solution by showing phase separation at intermediate compositions and temperatures (a miscibility gap).
A regular solution can also be described by Raoult's law modified with a Margules function with only one parameter
It can also be shown using the Gibbs-Duhem relation that if the first Margules expression holds, then the other one must have the same shape.
A regular solutions internal energy will vary during mixing or during process.
can be interpreted as W/RT, where W = 2U12 - U11 - U22 represents the difference in interaction energy between like and unlike neighbors.
The term was introduced in 1927 by the American physical chemist Joel Henry Hildebrand.