The extraction of trace amounts of gold from different aqueous mineral acid solutions by diphenyl-2-pyridylmethane dissolved in chloroform

Diphenyl-2-pyridylmethane, a high molecular weight substituted pyridine has been examined and found to be a useful solvent extraction reagent. Its behaviour is similar to amines in that it forms salts with mineral acids. The acid ionization constant (pK_BH ⁺) determined spectrophotometrically has a value of 4.41±0.06 at 25 °C. A study of the partition behaviour of trace amounts of gold between mineral acid solutions and 0.1M diphenyl-2-pyridylmethane dissolved in chloroform indicates that the metal can be quantitatively extracted from dilute mineral acid solutions and also from concentrated hydrochloric acid media in a single extraction. Attempts have been made to gain an understanding of factors affecting the extraction of gold. Common anions have little effect on extraction in concentrations upto 1M. Separation factors of a number of metal ions relative to gold are reported for three mineral acid systems; and gold has been estimated in some synthetic samples using neutron activation technique by prior extraction with 0.1M solution of diphenyl-2-pyridylmethane dissolved in chloroform.