Zimm plot

A diagrammatic representation of data on scattering from large particles, corresponding to the equation:
K c Δ R θ = 1 M ̄ w P θ + 2 A 2 c + ...
and used for the simultaneous evaluation of the mass average molar mass, M ̄ w, the second virial coefficient of the chemical potential, A 2, and (usually) the z-average radius of gyration, s 2 z 1 2; c is the mass concentration of the solute, Δ R θ the excess Rayleigh ratio, and P θ the particle scattering function that comprises (usually) the z-average radius of gyration. K depends on the solute, the temperature and the type of radiation employed. Several modifications of the Zimm plot are in frequent use; the most common one uses the excess scattering instead of the excess Rayleigh ratio.
Purple Book, p. 66