The linearized approximation for the correlation functions of a binary alloy, developed in parts I and II by the authors, is here applied to the experimental measurement of the diffuse scattering of x rays, thermal neutrons, and electrons. Information on the magnitude, sign, and range of the pairwise interactions has been extracted from the data on several alloys and alloy systems. The copper-gold system seems to be characterized by an oscillatory interaction out to at least third neighbors. The data on CuPt can be explained in terms of first- and second-neighbor energies, as can the results on Au3Mn, Ni4Mo, and CuNi, the latter being a clustering alloy. The results for β-CuZn are discussed in terms of a possible long-range oscillatory interaction, and an experiment is suggested for this alloy which would help to determine the presence of such an interaction.