Beryllium forms a red violet 1:1 complex with khimduchlo rophosphonazo-I rapidly in the presence of hexamethylene-tetramine buffer (pH 5)，which exhi- bits maximum absorbance at 590 nm (molar absorptivity=9.44× 103 L.mol-1· cm-1).Beer's law is obeyed for solution containing 0-25 µg of beryllium in 25m1 of solution. Interfering ions can be masked by the addition of small amounts of EDTA.