In contrast,
the solubility of maleic acid is unchanged by the addition of
caffeine in the more concentrated region of the phase diagram implying little change in relative strengths of the intermolecular interactions, again consistent with the binary system. Presumably, since caffeine is so weakly solvated by acetone, the presence of an H-bonding second solute can have a significant effect. Maleic acid on the other hand is already well solvated by acetone so that the addition of caffeine makes little difference.