Measurements of speeds of sound u have been made in binary mixtures of n-butanol (n-C4H9OH) with n-pentane (n-C5H12) at T = 298.15 K, and in the mixtures of n-C4H9OH with n-hexane (n-C6H14), or n-heptane (n-C7H16), or n-octane (n-C8H18), or 2,2,4-trimethyl pentane {2,2,4-(CH3)(3)C5H9} at T = 303.15 K. Values of u have been used to calculate the apparent excess speeds of sound hu and the isentropic compressibilities kappa(S) for these mixtures. The excess isentropic compressibilities kappa(S)(E) have also been calculated from the values of kappa(S). The kappa(S)(E) values have been found to be highly negative for {xn-C4H9OH + (1 - x)n-C4H12}. The values of kappa(S)(E) have been found to be positive at lower mole fractions of n-C4H9OH and negative at its higher mole fractions for {xn-C4H9OH + (1 - x)n-C6H14}, {xn-C4H9OH + (1 - x)n-C6H14}, {xn-C4H9OH + (1 - x)n-C6H14}, and {xn-C4H9OH + (1 -x)2,2,4-(CH3)(3)C5H9}. The inversion of sign in kappa(S)(E) occurs at x approximate to 0.11, x approximate to 0.60, x approximate to 0.89, and x approximate to 0.26, respectively, for these mixtures. The Delta u and kappa(S)(E) have been fitted with smoothing equations.