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 (phi(k)), and apparent molar volume (phi(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.