The effect of binary aqueous mixtures of ethylene glycol (EG), formamide (FA), N-methylformamide (NMF), dimethylformamide (DMF), and their pure phase on the apparent molar volume phi(V) of the bolaamphiphile decamethonium bromide (C10Me6 has been investigated at 298.15 K. The behavior of standard molar volumes V-2(0) and transfer volumes Delta(t)phi(V) of C10Me6 from water to solvent/water (S[W) binary mixtures, shows different minima and maxima depending on the composition of the solvent. This behavior is influenced by the nature of the cosolvent and on the type of the solute and more or less corresponds to VOlUmetric changes in the S[W mixture. The investigation of the transfer volumes in different fixed concentrations reveals an inversion of Delta(t)phi(V) values between the compositions, which suggests a differentiation of the effects of different volume contributions on the partial molar volume of ions. The correlation of Delta(t)phi(V) with the dielectric constant of the aqueous amide mixtures shows that the behavior of Delta(t)phi(V) vs x(amide) reflects the changes of epsilon(E) vs -x(amide). (c) 2005 Elsevier Inc. All rights reserved.