The speed of sound in solutions of zirconyl soaps (caproate, caprylate, and caprate) in xylene + methanol (volume ratio of 4:1) increases with increasing concentration and chain length of the soap. The isentropic compressibility (k s ), apparent molar compressibility (φ k ), and apparent molar volume (φ v ) were evaluated, and the results were explained in terms of solute-solvent interactions. It is concluded that the soap molecules do not aggregate appreciably below the critical micellar concentration.