Kristy M. Blyth, David N. Phillips, and Wilhelm van Bronswijk
School of Applied Chemistry, Curtin University of Technology, Perth, Western Australia 6845
The fire-assay technique is the oldest and most reliable method for the analysis of gold in gold-bearing ores and remains to this day the industry standard method. This article describes a laboratory exercise for the analysis of gold using the fire-assay technique. This method of analysis not only provides students with an introduction to the technique of fire assay, but also covers some very interesting acid–base and redox chemistry. The gold is collected in a lead button while the remainder of the constituents find their way into a slag. The gold is recovered from the lead by absorption in a bone–ash cupel. After dissolution of the silver in concentrated nitric acid, the remaining prill is dissolved in aqua regia and the gold determined by flame atomic absorption spectrometry. Pooling the class data enables the student to gain a full understanding of the roles of the various components of the flux.
Supplement
Instructions for students and notes for the instructor are available.
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