the ultrasonic velocity, density and viscosity of some schiff bases of 4-amino benzoic acid  were measured in 1,4-dioxane and dimethylformamide at 308.15 k. various acoustical properties such as isentropic compressibility (ks), rao’s molar sound function (rm), the van der waals constant (b), molar compressibility (w), inter molecular free length (lf), relaxation strength (r), internal pressure ...