The Spectrophotometric Determination of Thorium(IV) with Bromopyrogallol Red

Abstract

Abstract Bromopyrogallol red reacts with thorium(IV) to form a stable complex with an absorption maximum at 645 mμ against a reagent blank. The maximum absorbance is obtained in the pH range of 5.6 to 5.9 when the solution is heated in a boiling water bath for 20 min. The color system obeys Beer’s law in the range 6 to 106 μg of thorium in 25 ml. The molar absorptivity of the complex is calculated to be 5.0×104 at 645 mμ. The sensitivity of the reaction is 0.004 μg thorium per cm2. The complex has the composition 1 to 2 in metal to ligand. The effect of diverse ions on the determination is also examined.