Extraction-photometric determination of molybdenum in zirconium-, nickel- and iron-base alloys using oxine

An extraction-photometric method for the determination of molybdenum in zirconium-, nickel- and iron-base alloys was established. One gram of zirconium-base alloys is dissolved in 10 ml each of sulfuric acid and 50% ammonium sulfate solution by heating. Molybdenum oxinate is formed by adjusting the pH to 0.851.2 in the presence of 10 ml of 5% oxine solution. The oxinate is extracted by shaking vigorously for 1 min. with 10 ml of chloroform. The chloroform solution is washed by shaking for 1 min. with 50 ml of 0.1 M oxalic acid solution. After the drying of the solution with anhydrous sodium sulfate, the absorbance is measured at 380 nm. Nickel- and iron-base alloys are dissolved in the mixed acid (nitric acid : hydrochloric acid : water = 1 : 1 : 1) by heating. The formation and extraction of the oxinate is carried out by the same way as described above except for analyzing a sample containing more than 0.01 g of iron. One gram of iron can be masked by addition of 2 g of ascorbic acid and adjusting the pH to 1.52.0. Less than 0.5 mg of tungsten is masked by addition of 0.2 g of fluoride ion before the extraction. According to this method, molybdenum in these alloys can be determined rapidly below the order of a few ppm.