A novel method has been described for the spectrophotometric determination of proteins, which was based on a fading reaction between chrome blue SF and proteins to form complexes in clark-lubs buffer at pH 1 .0 - 2.0. The decrease of absorbance was proportional to the concentration of proteins. Beer's law is obeyed in the range from 0 - 50 mg/L to 0 - 80 mg/L on die different proteins. The reactions have highly sensitivities and their apparent molar absorptivities of fading reactions are between 8.0 × 104L·...