Abstract: A new method is reported for spectrophotometric determination of trace amounts of chromium based on decoloarizing reaction of arsenazo M by Cr（VI） in H2SO4 medium.The fading in color is directly proportional to the amounts of chromium.The maximum absorption is at 550?nm and the apparent molar absorptivity is 2.33×104?L·mol-1·cm-1.The linear range is 0～1.2?mg/L of Cr（VI）.The method has been applied to the determination of trace chromium in soil with satisfactory results.

Key words: chromium； arsenazo M； decolourizing reaction； spectrophotometry；