In an acetic acid-sodium acetate buffer solution of pH4.7,aluminium（Ⅲ）reacts with DBC-chlorophosphonazo to form a violet blue complex.The composition of the complex is 1∶1.The maximum absorption of the complex exhibits at 620 nm and the molar absorptivity is 1.38×104 L·mol-1·cm-1.Beer’s law is obeyed over the range of 0—35 μg of aluminium per 25 mL solution.The method was used in the determination of trace amout of aluminium in sodium carbonate and water samples with satisfactory results.
In the medium of 0.60 mol/L nitric acid,chromium（Ⅵ）reacts with DBC-arsenazo to produce color-fading reaction.Chromium（Ⅵ） was determined based on this reaction.The aqqarent molar absorptivity of the method is ε520nm=2.31×105L·mol-1·cm-1.Beer’s law is obeyed over the range of 1.0-8.0μg/25mL of chromium（Ⅵ）.The method was applied to the determination of chromium in the soil samples.
