Merrill-Crowe Trial
The Merrill-Crowe process is a separation technique used to remove gold as well as silver and copper from a cyanide solution .
The rock is separated from the gold cyanide solution by filtration or a countercurrent decanter . The solution is then passed through special filters, which usually consist of kieselguhr . The oxygen contained in the solution is then removed in a vacuum ventilation system. In this system z. B. a rotating distributor disc the solution evenly as a thin film on the inner wall of the container. The air bubbles contained in the solution expand and burst due to the vacuum in the container and are sucked out by the vacuum pump.
Then zinc dust is added to the cleaned, oxygen-free solution. Since zinc has a higher chemical affinity for the cyanide ions than gold , the gold settles. If silver or copper is present in the solution, these will also be deposited by adding zinc dust.
The deposited precious metal is filtered out of the solution and treated with sulfuric acid to dissolve zinc residues. This solution is filtered again and the remaining gold is melted down into raw bars. The raw bars are further cleaned in a metal refinery , which removes the foreign metals such as copper or silver contained in the gold and produces the desired degree of purity of the gold.
The basic process was invented and patented by Charles Washington Merrill around 1900; it was later improved upon by Thomas B. Crowe, who worked for the Merrill Company.
Today electrometallurgy is an alternative to the Merrill-Crowe process.
See also
Individual evidence
- ↑ a b The Merrill Crowe Recovery Process. In: Denver Mineral Engineers Inc. 2012, accessed August 13, 2012 .
- ^ A b Wong Wai Leong Eugene / Arun S. Mujumdar, National University of Singapore: Gold Extraction and Recovery Process. (PDF; 991 kB) (No longer available online.) March 2009, archived from the original on August 13, 2012 ; accessed on August 13, 2012 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ^ Merrill Crowe Recovery Process. (No longer available online.) In: Gold Avenue Encyclopaedia. 2012, archived from the original on July 7, 2013 ; accessed on August 13, 2012 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ Ryder, David Warren: The Merrill Story (Life and Work of Charles Washington Merrill and History of the Merrill Company), Merrill Co., 1958 (English).
