Characterizations of silver alloys used in modern Mexican coins

Journal Article · Tue Sep 15 04:00:00 EDT 2009 · Materials Characterization

DOI:https://doi.org/10.1016/J.MATCHAR.2009.04.010· OSTI ID:22082780

Mendoza-Lopez, M L ^[1]; Perez-Bueno, J J ^[2]

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1. Instituto Tecnologico de Queretaro, Avenida Tecnologico S/N, Queretaro, Qro, C.P. 76000 (Mexico)
2. Centro de Investigacion y Desarrollo Tecnologico en Electroquimica, Parque Tecnologico Queretaro-Sanfandila, Pedro Escobedo, Qro., C.P. 760703 (Mexico)

This paper presents a complete methodology for the characterization of silver alloys used in modern coin production. Mexican coins with a nominal silver concentration from 10% to 99.99% were used in this study. Calibrated Glow Discharge Optical Emission Spectrometers were used to determine the chemical composition of the alloys as a function of the depth, while inductively coupled plasma was used to determine the total element composition in bulk. Scanning Electron Microscope was used to study the phase distributions in the different silver coins. According to Glow Discharge Optical Emission Spectrometers and inductively coupled plasma, the silver content found in the studied samples was consistently greater than that of the nominal silver content reported by the Mexican mint. This may lead to a review of the new methods of analysis used nowadays in contemporary coin minting. This result is very important because silver is increasing in value as metal and, considering the volume of production of silver coins, this may increase further as a consequence of a growing popular confidence in silver currency. In the case of silver studies, an advantage of the absence of silver detector in the Glow Discharge Optical Emission Spectrometers system is that it allows for the recalibration to have a better range of detection of other metals present in the alloys. A calibration curve using the copper content obtained by inductively coupled plasma (bulk) and Glow Discharge Optical Emission Spectrometers (depth profile) was performed. The relevance of control in modern silver coin minting was clarified, especially in minimizing the discrepancy between the nominal and the core fineness. The physical and chemical properties of the alloys studied are defined, revealing important variations in silver and copper contents. A new methodology and metrology for the control of coinage are suggested.

• OSTI ID: 22082780
• Journal Information: Materials Characterization, Journal Name: Materials Characterization Journal Issue: 9 Vol. 60; ISSN 1044-5803; ISSN MACHEX
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
CHEMICAL COMPOSITION
CHEMICAL PROPERTIES
COPPER
EMISSION SPECTROSCOPY
GLOW DISCHARGES
ICP MASS SPECTROSCOPY
MEXICO
QUANTITATIVE CHEMICAL ANALYSIS
SCANNING ELECTRON MICROSCOPY
SILVER
SILVER ALLOYS