where # is a constant, $ and + are the concentration and molar mass of the analyte, respectively, 4 is the wavelength of the incident light, ' is the scattering angle, 3 # is the index of refraction of the solvent, and % is the Rayleigh ratio, or the scattering intensity above baseline at each detector angle (Figures ). For environmental colloids, #, $, and + are usually unknown, but " ! " can be estimated by regressing % $% on 567 " ('/2).