page_title: Gold parting
section_title: Post medieval to Modern Period
hierarchical_section_title: Gold parting / History / Post medieval to Modern Period
caption_attribution_description: De re metallica title page
context_page_description: Gold parting is the separating of gold from silver. Gold and silver are often extracted from the same ores and are chemically similar and therefore hard to separate. Over the centuries special means of separation have been invented.
  The very earliest precious metals had mixes of gold and silver; gold and silver alloy is called electrum. With the advent of coinage, methods had to be invented to remove impurities from the gold so that gold of specific purities could be made. Cupellation was able to remove gold and silver from mixtures containing lead and other metals, but silver could not be removed. Gold parting as a process was specifically invented to remove the silver. The main ancient process of gold parting was by salt cementation and there is archaeological evidence of that process from the 6th century BC in Sardis, Lydia. In the post-medieval period parting using antimony, sulfates and mineral acids was also used. In the modern period chlorination using the Miller process, and electrolysis using the Wohlwill process are the most widely used methods of refining gold by removing silver and platinum. These latest processes have been employed for over 100 years.
context_section_description: Comprehensive accounts of the salt cementation processes is given by; Biringuccio in  his The Method of cementing gold and of Bringing it to its Ultimate Fineness.; in the Probierbuchlein – Little Books on Assaying; by Georgius Agricola in book 10 of De Re Metallica; and by Ercker in his Treatise on ores and assaying. This was a period where new techniques began to be explored. Granulation of the gold instead of gold foil increased surface area and therefore the efficiency of the reaction. Salt cementation continued to be the main method of parting until the 16th century but in later Middle Ages processes using sulfur, antimony and mineral acids began to be used. There are archaeological finds at sites in London of distillation vessels for making acids in Britain from the 15th century which include fragments of ceramic cucurbits (vessels for heating reacting chemicals) which were used with alembics for distillation. By the 18th century cementation was rarely used and had been replaced by acid treatment. Into modern times the acid parting method continued to be used but other methods were discovered. In 1860s Australia the Miller process was developed, this removed silver by bubbling chlorine gas through the molten gold mixture. Soon after, in the 1870s, Electrolytic refining of gold was developed, the Wohlwill process, to deal with the problem of removing platinum from the gold. This technique is the most commonly used today.
caption: Title page of the 1556 edition of Argicola's De Re Metallica
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