Abstract
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.
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Stefano Caporali graduated in Chemistry in 1998 and received his Ph.D degree in Materials Science from University of Florence (Italy) in 2006. His research interests cover a wide range of applied and theoretical aspects of electrochemistry and surface chemistry in both aqueous and non-aqueous environments.
Silvano Bellandi graduated in Biology at the University of Florence in 1980, since 1987 he works in Analytical Strumental Chemistry and since 2005 in Electrochemistry with regard to nanomaterials and methods for determination of trace metals.
Massimo Innocenti graduated in Chemistry at the University of Florence in 1989; since November 2002, he is researcher in ElectroAnalytical Chemistry. The scientific activity concerned different topics, all of them in the field of Electrochemistry, with a particular attention to the electrodeposition of metals and semiconductors under morphological control.
Ornella Lopilato graduated in Chemistry at the University of Florence in 2007. She is working in ElectroAnalytical Chemistry and her scientific activity concerned the use of electrochemical techniques for the determination of environmental pollutant.
Lorenzo Romualdi graduated in Chemistry at the University of Florence in 2010. His scientific activity concerned the use of electrochemical techniques for the determination of precious metals.
Giovanni Pezzatini is associate professor of Analytical Chemistry in the University of Florence. Since 1982 he was teaching different analytical subjects in Florence and Siena Universities. He is the author of 70 research papers in international journals, concerning electroanalytical chemistry. This last is the subject in which he is now encharged in the department of chemistry of Florence University.
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Caporali, S., Bellandi, S., Innocenti, M. et al. Determination of gold in alloys via potentiometric titration; an alternative to the fire assay. Gold Bull 43, 122–130 (2010). https://doi.org/10.1007/BF03214977
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DOI: https://doi.org/10.1007/BF03214977