メチルキシレノールブルーによるビスマスの比色定量

概要

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Bismuth formed a red-violet complex with Methylxylenol Blue (MXB) in an aqueous solution, and it was applied for a colorimetric determination of bismuth. The complex had an absorption maximum at 575 mμ, and the absorbance was constant over the pH range from 1.2 to 1.3. Beers law was obeyed over the range from 20 to 180 μg of bismuth in 25 ml solution. The molar extinction coefficient was about 8900. The established analytical procedure was as follows.The sample solution containing 20 to 180 μg bismuth was mixed with suitable amounts of 0.2N HNO3 and 1.0ml of 0.1% MXB, and made up to 25 ml with water (the final pH 1.21.3). After 5 minutes, the absorbance was measured at 570 mμ against the reagent blank. Iron (III), thorium (IV) and molybdenum (VI) interfered, but the permissible amount of iron (III) was increased by addition of L-ascorbic acid. This method was simple and the results of recovery tests on synthetic samples (lead+bismuth) were satisfactory.