Studies on density of substituted indole-3-carboxaldehyde in the mixture of benzene + methanol have been made. The cmc values in higher volume percent of methanol are higher than those in higher volume percent of benzene. Masson equation has been applied successfully to interpret apparent molar volume of compounds in benzene +methanol. The studies suggest that interactions between solute solvent molecule increases when non-polar hydrocarbon is predominant in solvent mixture whereas solute-solute interactions increases when methanol is predominant at below and above cmc.