Search results
Results from the WOW.Com Content Network
The Wohlwill process is an industrial-scale chemical procedure used to refine gold to the highest degree of purity (99.999%). [1] The process was invented in 1874 by Emil Wohlwill . This electrochemical process involves using a cast gold ingot , often called a doré bar , of 95%+ gold to serve as an anode .
Craddock, P. T. 2000a Historical Survey of Gold Refining: 1 Surface Treatments and Refining Worldwide, and in Europe Prior to AD 1500. In A. Ramage and P. T Craddock (eds) King Croesus' Gold; Excavations at Sardis and the History of Gold Refining. London: British Museum Press, 27–53. ISBN 978-0-674-50370-0, 0-674-50370-8
Gold extraction is the extraction of gold from dilute ores using a combination of chemical processes. Gold mining produces about 3600 tons annually, [1] and another 300 tons is produced from recycling. [2] Since the 20th century, gold has been principally extracted in a cyanide process by leaching the ore with cyanide solution.
Refining is the removal of impurities from materials by a thermal process. This covers a wide range of processes, involving different kinds of furnace or other plant. The term "refining" can also refer to certain electrolytic processes. Accordingly, some kinds of pyrometallurgical refining are referred to as "fire refining".
In metallurgy, refining consists of purifying an impure metal. It is to be distinguished from other processes such as smelting and calcining in that those two involve a chemical change to the raw material, whereas in refining the final material is chemically identical to the raw material. Refining thus increases the purity of the raw material ...
Extractive metallurgy is a branch of metallurgical engineering wherein process and methods of extraction of metals from their natural mineral deposits are studied. The field is a materials science, covering all aspects of the types of ore, washing, concentration, separation, chemical processes and extraction of pure metal and their alloying to suit various applications, sometimes for direct ...
The chemical reaction for the dissolution of gold, the "Elsner equation", follows: 4 Au + 8 NaCN + O 2 + 2 H 2 O → 4 Na[Au(CN) 2] + 4 NaOH. Potassium cyanide and calcium cyanide are sometimes used in place of sodium cyanide. Gold is one of the few metals that dissolves in the presence of cyanide ions and oxygen.
Metal refineries refining metals such as alumina, copper, gold, lead, nickel, silver, uranium, zinc, magnesium and cobalt; Iron refining, a stage of refining pig iron (typically grey cast iron to white cast iron), before fining, which converts pig iron into bar iron or steel [1]