The conductometric, viscometric and ultrasonic velocity measurements of the solutions of terbium laurate in benzene-methanol mixture (7:3 v/v) were carried out at 40 ± 0.05°C. The conductivity results showed that the soap behaves as a weak electrolyte in dilute solutions. The viscosity results were explained on the basis of equations proposed by Einstein, Vand, Moulik and Jones-Dole and the values of molar volume evaluated by using Einstein's and Vand's equations were in close agreement. The ultrasonic velocity measurements were used to evaluate various acoustic parameters. The results showed that the soap-soap interactions are weaker than soap-solvent interactions in dilute solutions and the soap molecules do not aggregate below the critical micelle concentration in dilute solutions.