Diapycnal mixing occurs at spatial scales which are unresolved in numerical models of the ocean. Thus, it is essential to understand small-scale mixing processes properly in order to parameterize their fluxes in numerical models, especially those used in climate studies. In the ocean, diapycnal mixing is actually a process of mixing two variables, heat (or temperature) and salt (or salinity), which both contribute to the density of ocean water. Presently, numerical ocean models parameterize the unresolved diapycnal fluxes as an eddy diffusivity times a mean property gradient normal to the isopycnals. Most models also use the same eddy diffusivities for heat and salt. Mixing in the ocean interior is due mainly to breaking internal waves. In this paper, vertical fluxes and diffusivities of two tracers, with different molecular diffusivities, were obtained for a wide range of breaking internal wave activity in the laboratory.