Hansen split total δ 2 into three fractional cohesion parameters related to the following intermolecular forces: dispersion forces (δ d ), hydrogen bonding (δ h ), and polar forces (δ p ). Equation TO4 has been developed for a single-component system for associated solutions with no or only positive deviations from Raoult's law. We expanded this equation to multicomponent systems assuming the additivity principle, which states that the influence of each component in the system is proportional to its volume fraction in terms of enthalpic contribution: