The partial molal volumes of a series of homologous tetraalkylammonium iodides, bromides and chlorides in a series of ethanol-water mixtures have been determined at 30 ℃. It was found that general trend in variation of anionic partial volumes V^o_x- with the solvent composition is the same for all the anions studied, i.e., Cl^-, Br^- and I^-, and that absolute values V^o_x-increase with the size of anions in all solvent compositions.
The results also indicate that at 0.1 mole fraction ethanol the maximum stucturedness of water causes a minimum in the tetraalkylammonium cation partial molal volumes, while at 0.2-0.3 mole fraction the solvent structure is such that the free volume is a minimum and the electrostrictive effect of halides ion is a maximum.