In mixtures of alkanoic acids (A) and alkylamines (B) the behaviour of the systems is largely determined by a proton transfer from the acid to the amine with a subsequent formation of a complex in an equimolecular ratio (A₁B₁). Provided the alkyl chains are sufficiently long and contain an equal number of carbon atoms, an equimolecular mixture of acid and amine behaves like a catanionic surfactant and forms a lamellar liquid crystalline phase in water. Since alkylamines with seven or more carbon atoms in their alkyl chain also form lamellar liquid crystalline phases in water at room tem- perature, the ternary phase diagrams water-alkanoic acid-alkylamine are dominated by a large lamellar phase in equilibrium with almost pure water.

However, if the balance in alkyl chain length between the acid and the amine is altered, i.e., one component contains more carbon atoms than the other, the situation becomes different. The formed alkylammonium alkanoate now resembles an ionic surfactant with an organic counterion. In this case the distribution of the counterion between the aggregates and bulk water determines the phase behaviour. For an intermediate situation a solution phase is favoured over liquid crystalline phases, and solution phases covering almost all mixing ratios with water are formed.