Mining Gold and Silver Bullion Analysis
SGS has a global network of laboratories, offering you an unparalleled level of analytical expertise around the world. For gold and silver bullion analysis and assay there are many different methods available, for example silver bullion can be analysed by cupellation, by chemical titration, or by a combination of chemical titration and instrumental techniques.
SGS experts are always available to assist you with selecting the analytical technique that is fit for your purposes. In fact, the critical aspect of bullion analysis is proper sampling. The gold or silver must be sampled while it is still molten. The most reliable technique involves the use of a vacuum sampler.
Once sampled, gold bullion samples are usually about 0.5g in size and are cupelled with enough silver to give a Ag:Au ratio between 2:1 and 4:1. This will result in a successful parting. The bead remaining after cupellation is rolled into a very thin strip called a coronet. The Au result is obtained by parting (dissolving the silver with nitric acid to leave the gold) the coronet in dilute nitric acid. This dissolves Ag but not Au, and the remaining Au is weighed. A sample of proof Au of the same weight as the sample is treated at the same time. The sample result is corrected for any gain or loss (called the surcharge) according to the result from the proof gold. Samples are usually run at least in duplicate.
Silver bullion analyses can be analysed by cupellation, by chemical titration, or by a combination of chemical titration and instrumental techniques. The cupellation process is subject to volatilisation errors that must be corrected. The errors inherent in the cupellation method can be avoided by the wet chemical method. This method consists of dissolving a 1g sample of bullion in nitric acid. After this stage, the finish can be either titration or instrumental.
SGS has an intensive, ongoing programme to monitor quality in all our labs. Dozens of our labs carry internationally and industry recognised certifications and accreditations. Scopes vary among laboratories.
Partner with SGS today and find out how our expertise can give you accurate and reliable gold and silver bullion results.