Determination Of Gold In Alloys Research Articles

Determination of gold in alloys via potentiometric titration; an alternative to the fire assay

In this paper we report the results of a deep investigation of gold title in jewellery alloys by means of potentiometric titration. After reviewing the suitable reactions for such purpose we focused on the most profitable one, which involves the use of hexadecylpyridinium chloride (CPC). This cation gives rise to selective and quantitative precipitation of AuCl4 −. We completely revised a method previously proposed by W.S. Selig in the 80’s, by improving the sampling preparation and by optimizing the titration steps. Then, the new proposed method was tested on a large number of different alloys, commonly used for goldsmithery purposes. The obtained gold titles were compared with the data achieved by fire assay, giving rise to a very good agreement. At the light of these results, the present method can be rightfully considered a cheaper and “greener” alternative to the traditional one.

2,3-Dichloro-6-(3-carboxy-2-hydroxy-1-naphthylazo)quinoxaline as an Analytical Reagent for the Spectrophotometric Determination of Microamount of Gold(III)

Abstract The synthesis, spectral characteristics, and analytical application of 2,3-Dichloro-6-(3-carboxy-2-hydroxy-1-naphthylazo)quinoxaline (DCHNAQ) are described. A simple, rapid, selective, and sensitive spectrophotometric method for the determination of microgram amounts of gold, alone, or in the presence of associated metals, is developed, based on the color reaction between the metal ion and the reagent. The yellowish brown complex (λmax = 575 nm) has stoichiometric ratio (1 : 1) [metal : ligand] over the pH range 3.4 to 7.0. Beer’s law is obeyed over the concentration range 0.1—6.9 μg cm−3 of gold. The molar absorptivity and Sandell’s sensitivity of the method are 1.52 × 104 dm3 mol−1 cm−1 and 0.016 μg Au cm−1 respectively. The relative standard deviation for six replicate determination of 2.95 μg cm−3 of gold(III) is 1.37%. The interference of various ions has been studied and conditions were developed for the determination of gold in alloys and some synthetic samples without the need for extraction or heating.

A new, simple, and rapid method for the quantitative separation and determination of gold in gold-silver-copper alloys

The separation and determination of gold in alloys could be done using 2 M KCNO by direct precipitation of gold and weighing it as gold cyanate. Complete recovery of gold is obtained. The remaining metals could be separated by extraction. The results are applied to “Gold Solder” 14 carat.

Potentiometric redox determination of gold(III) and its application to alloys

The simple potentiometric method proposed for the indirect determination of 1–10 mg of gold(III) is based on reduction to the metal with excess of cobalt(II) in the presence of 1,10-phenanthroline or 2,2'-bipyridine at pH 3 and 50°C, and titration of the unused cobalt(II) complex with iron(III) chloride solution. Many metal ions can be tolerated; Ag(I) and Pd(II) are eliminated by precipitation with sodium chloride and 1,10-phenanthroline or 2,2'-bipyridine, respectively, but Hg(II), Fe(III) and Pt(IV) interfere. The method is applied to the determination of gold in alloys.

Direct Spectrophotometric Determination of Gold in Alloys as Chloroaurate

AbstractA method is presented for a simple and direct determination of gold in alloys, utilizing a preliminary separation of gold from an alloy, and its subsequent conversion to chloroauric acid.The optical density of the chloroaurate ion is measured at two selected wavelengths, calculating the gold content of alloys by using the absorbance difference technique as developed by Glasner and Avinur. A suitable technique enables wide‐range determination in various samples of gold alloys ranging from 0.001% to over 90% gold content. Platinum does not interfere when present in small amounts in the alloy.

Gravimetric Determination of Gold in Alloys

AbstractA method is presented for the gravimetric determination of gold in alloys. Based on a known procedure used in metallurgy, it involves the separation of gold from the other elements constituting the alloy, by the aid of the “parting process”, suitably modified. It involves a relatively simple technique with a high degree of accuracy. Gold was successfully determined in the presence of the following metals: Ag, Cd, Cu, Cr, Fe, Mn, Ni, Pd, Sn, Zn.Platinum seriously interferes with the analysis.