The prediction of the solubility of active pharmaceutical ingredients (APIs) is a significant challenge which
is of importance in pharmaceutical applications and solvent selection. Here, we extend the table of group
interactions (3 like interactions, 47 unlike interactions) of the SAFT-γ Mie group-contribution equation of
state to model the phase behaviour and solubility of mefenamic acid, a nonsteroidal anti-inflammatory
drug, in a range of solvents. In addition to mefenamic acid, we also consider its molecular synthons:
benzoic acid and diphenylamine. New experimental solubility data are presented for the three molecules
in a range of solvents, and three new SAFT-γ Mie functional groups are defined (aCCOOH, aCNHaC and
CH3CO) and characterised, together with their interactions with solvent groups. Literature data for the
vapour pressure, single-phase density, saturation density, vapourisation enthalpy, bubble temperature,
dew temperature, and bubble pressure are used to characterise the new group interactions. Solubility
data are used to characterise the new group-group interactions only if there are no other experimental
data available. The transferability and predictive accuracy of the new models are assessed by comparing the theoretical predictions with the experimental solubility data. Our comparison includes alcohols,
ketones, and esters as families of solvents and mixed-solvent solubility predictions.