Concentration dependence of the osmotic and activity coefficients of imipramine and clomipramine hydrochlorides in aqueous solution

Vapor pressure lowering of the two antidepressant drugs imipramine and clomipramine hydrochloride solutions in the concentration range 0-0.28 mol.kg(-1) at 303.15 K were determined. For imipramine hydrochloride, measurements at 308.15 and 313.15 K were also made. From these results, the osmotic and activity coefficients for both compounds were calculated, and their concentration dependence was studied. An inflection point was detected for each substance, identified as a critical concentration.