Colloidal chemical behaviour and micellar characteristics of lithium caprate and laurate in benzene-methanole mixtures have been investigated by ultrasonic velocity and density measurements (313 K). The variation of adiabatic compressibility, intermolecular free length, apparent molal compressibility, apparent molal volume, molar sound velocity primary salvation number show that there is sufficient soap solvent interaction due to which micellar alignment is considerably affected. The results indicate that CMC values decrease with the increase in number of carbon atoms in the hydrophobic chain. The study reveals that change in the micellar organization takes place around 40 percent methanol concentration. Ultrasonic investigations provide revealing interpretations of soap-solvent interaction and structural insight of micelles.