Equations are derived, in terms of the derivative of the osmotic pressure with respect to concentration, for light scattering and sedimentation (transport and equilibrium) of polyelectrolyte systems comprising a solvent component 1, a macromolecular component 2, and an added simple electrolyte component 3. It is shown by thermodynamic arguments that, when suitable restrictions are applied to the chemical potential of component 3, the equations for the threehyphen;component systems become formally identical with the equations for twohyphen;component systems. A striking similarity is achieved between the equations for light scattering and sedimentation, by direct use in the latter of the derivative of the solution density with respect to concentration, instead of the more familiar buoyancy terms. The extension of the equations to more than one supporting electrolyte is immediate, and the extension to a macromolecular component inhomogeneous with respect to molecular weight may be achieved by known methods.
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