If the mixture parameters of an equation of state can be expressed as a linear combination of pure component parameters and the phase molar compositions, then the component fugacities can also be expressed as a linear combination of pure component parameters with coefficients only depending on mixture properties. As a result Henry constant is then available without any computation for any solute, as soon as the parameters describing the solvent have been calculated. A further extension of the same approach to phases in equilibrium leads to the same type of relation for the equilibrium constants. Thereby infinite dilution K-values can be obtained exactly without any further computation.Based on these results a consistent procedure for the estimation of equilibrium constants in the more classical cases of finite dilution has been developed. It can be used when moderate binary interaction parameters are used. A potential application of such a procedure is the delumping of pseudo-components, i.e. the prediction of the detailed composition of the phases resulting from a flash calculation just performed on a lumped mixture.The method is described in detail and a number of examples are proveded in this paper. The method has been tested on two and four parameter cubic equations of state. Particular attention has been given to the conditions of temperature and pressure where the lumping process changes the number of phases.