Spectrophotometric determination of magnesium in metallic tellurium

Abstract

The spectrophotometric determination of trace amounts of magnesium in metallic tellurium using Xylidyl-Blue-II (XB-II) has been studied.
According to the foregoing reporters, the alkalinity of test solutions should have been pH 9.0 (with borax buffer). But, the absorption spectra of XB-II and Mg-XB-II complex change with varying pH and ethylalcohol concentration. Provided that the range of ethylalcohol concentration is 5090%, the absorbance at 510 mμ of Mg-XB-II complex increases with increasing pH of the solution.
In the proposed procedure, the test solution is adjusted to pH 10.2 with ammonium chlorideammonia buffer.
The sample is dissolved with aqua regia and is evaporated to dryness. Tellurium is removed by precipitation as tellurium dioxide at pH 4.5 of nitric acidity and the other interfering ions are masked with potassium cyanide and triethanolamine.
Magnesium is determined spectrophotometrically at 510 mμ with the reagent blank as a reference.
Satisfactory results with an accuracy within 10% were obtained for practical samples by the proposed method.