Spectrophotometric Determination of the Ba Content in Si-Ca-Ba Alloy by Using Chlorophosphonazo as the Spectral Chromogenic Reagent

The colour reaction of chlorophosphonazo with barium(Ⅱ) was studied.And the effects of the coexistent ions on the colour reaction were also investigated.The results show that the chromogenic reagent(chlorophosphonazo) reacts with barium to form a stable green complex in NH3 ·H2O-NH4Cl buffer solution of pH10.0.The complex exhibits an absorption maximum at 670 nm with an apparent molar absorptivity of 6.49×104 L/(mol·cm).The spectrophotometric determination is of high sensitivity obeying Beer's law,when 25 mL sample solution contains 0~50 μg barium.The disturbance of Ba determination from Al and Fe can be sheltered by adding triethanolamine and 1,10-phenanthroline monohydrate,and Ca disturbance by adding EGTA-Pb.The Ba content in Si-Ca-Ba alloy can be determined by spectrophotometry with chlorophosphonazo,where the determined result is in good agreement with the certified value and the relative standard deviation(RSD) is less than 2%.