The molecule of 1,2-ethanediol, like that of water, is capable of forming two hydrogen bonds as a donor of protons. Consequently, the complexes of pyridine and its methyl derivatives with ethanediol may associate in the liquid phase in a similar way as those with water. The association contributes to the excess molar expansion making its isotherms W-shaped for the mixtures with 2-methylpyridine and 2,6-dimethylpyridine. Negative excesses of volume and compression are correlated with the association energies of the 1:1 amine-ethanediol complexes. They increase in the order: pyridine < 2-methylpyridine < 2,6-dimethylpyridine. (C) 2011 Elsevier B.V. All rights reserved.