GEORGE BERNARD / SCIENCE PHOTO LIBRARY GEORGE BERNARD / SCIENCE PHOTO LIBRARY
Separating gold from its ores, engraving. The workers are using quicksilver (mercury), which has a chemical affinity for gold. When mercury is added to finely crushed ore it dissolves the gold and forms amalgam, a process called amalgamation. Un-reacted mercury is removed from the amalgam by straining it through leather (7). The amalgam is then heated in an athanor furnace (1). Mercury has a lower melting temperature than gold, allowing its vapour to be collected in a receiver (3) and leaving pure gold (12). Taken from The Laws of Art and Nature, in Knowing, Judging, Assaying, Fining, Refining and Inlarging the Bodies of Confin'd Metals (1683) John Pettus, a translation of the work by Lazarus Erckern.
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