Extraction of gold(III) from low-grade ores with amidines followed by its spectrophotometric determination with methylene blue

A procedure is described in which gold(III) is quantitatively extracted with an amidine into chloroform over the acidity range pH 3.0–11.0 M HCl, followed by its selective spectrophotometric determination by interaction of the extract with methylene blue in the pH range 3.0–9.0. The molar absorptivity of the coloured complex formed by extraction with ten different amidines and methylene blue reaction lie in the range 1.1 × 104−6.5 × 104 1 mol−1 …