The Spectrophotometric Determination of Gallium(III) with Xylenol Orange

Abstract

Abstract The reaction between gallium (III) and xylenol orange has been studied spectrophotometrically in order to establish the optimum conditions for determining traces of gallium. Depending on the pH value of a solution, gallium (III) reacts with xylenol orange to form two complexes. The 1 to 1 complex which gives a maximum absorbance in the pH range from 1.2 to 1.7 has an absorption maximum at 530 mμ when measured against a reagent blank. The 1 to 2 complex which gives the maximum absorbance in the pH range from 4.5 to 5.5 has an absorption maximum at 502 mμ. Either with 1 to 1 and 1 to 2 complexes, Beer’s law is obeyed up to 60 mμ. of gallium. The apparent molar extinction coefficients of the 1 to 1 and the 1 to 2 complexes have been calculated to be 22900 and 16300 respectively. The present method is comparable in sensitivity with the stilbazo or the luminogallion IREA method. The addition of a small amount of fluoride is effective in eliminating some interfering cations, including aluminum (III), thorium(IV) and zirconium(IV).