Abstract—By idealizing the design of a typical spectrofluorimeter that measures fluorescence from dilute solutions, we are able to derive an equation that predicts the dependence of the observable amplitude on the concentration of the solute and on several instrumental parameters. The result of the derivation, the fluorescence function, is used together with measurements of rhodamine B fluorescence and colloidal silica scattering to calibrate a spectrofluorimeter.The fluorescence function and the calibration data are used to determine the absolute fluorescence quantum yield of quinine sulfate in 0–1 N H2So4. The results, Ø250=0.582 with excitation at 250 mμ, adn Ø350=0.577 with excitation at 350mμ. agree well with the previous evaluation of Melhuish, Ø3