A boundary layer theory of heat, mass and momentum transfer is proposed for Newtonian and non-Newtonian fluids both dependent and independent of time. Kolmogoroff's theory of local isotropic turbulence is extended to power law fluids and used to predict mass transfer rates. A theory about the diffusivity of solids to complex fluids – solutions of colloids and macromolecules – is also developed. A general method is suggested to correlate the shear friction factor of non-Newtonian laminar flow past surfaces of various shapes. A criterion for the often observed retardation of turbulence in non-Newtonian fluids is also proposed. The diffusivity of ortho-nitrophenol in aqueous Polycell solutions, the drag coefficient of spheres falling in power law fluids, the agitation of non-Newtonian fluids and the dissolution of spheres freely suspended in power law fluids are experimentally investigated. All the data gathered agree with the proposed theories.