Speeds of sound mu of {xC(2)H(5)OC(2)H(5) + (1 - x)C6H6} and {xC(2)H(5)OC(2)H(5) + (1 - x)CCl4} have been measured at T = 298.15 K. Values of mu have been used to calculate the isentropic compressibilities kappa(s) for these mixtures. The values of the excess isentropic compressibilities k(S)(E) have also been calculated and are found to be negative throughout the entire range of x. The quantity Delta u, which refers to the deviations of the experimental values of u from those obtained from a mixture law, has also been calculated.