Editing Gold cyanidation (section)

===Industrial process===
[[File:Jsmacarthur-X-007r.jpg|thumb|upright|[[John Stewart MacArthur]] developed the cyanide process for gold extraction in 1887.]]
The expansion of gold mining in the [[Witwatersrand|Rand]] of South Africa began to slow down in the 1880s, as the new deposits found tended to contain [[pyrite|pyritic ore]]. The gold could not be extracted from this compound with any of the then available chemical processes or technologies.<ref name="Gray">{{ cite journal |first1=J. A. |last1=Gray |first2=J. |last2=McLachlen
|title=A history of the introduction of the MacArthur-Forrest cyanide process to the Witwatersrand goldfields |journal=Journal of the Southern African Institute of Mining and Metallurgy |volume=33 |issue=12 |date=Jun 1933 |pages=375–397 |hdl=10520/AJA0038223X_5033}}</ref>
In 1887, [[John Stewart MacArthur]], working in collaboration with brothers Robert and William Forrest for the [[Charles Tennant|Tennant Company]] in [[Glasgow]], Scotland, developed the MacArthur–Forrest process for the extraction of gold from gold ores. Several patents were issued in the same year.<ref>{{cite patent
|inventor1-last=MacArthur |inventor1-first=John Stewart |inventor2-last=Forrest |inventor2-first=William |inventor3-last=Forrest Robert |inventor3-first=Robert |pubdate=1889-05-14 |title=Process of Obtaining Gold and Silver from Ores |country=US |number=403202}}</ref> By suspending the crushed ore in a cyanide solution, a separation of up to 96 percent pure gold was achieved.<ref>{{cite web |title=Methods to recover Gold II |date=2013-05-14 |url=https://suertegold.wordpress.com/in-the-beginning-there-was-gold-1/day-52/}}</ref>
The process was first used on the [[Witwatersrand|Rand]] in 1890 and, despite operational imperfections, led to a boom of investment as larger gold mines were opened up.<ref name="Recent Advances in Gold Metallurgy">Habashi, Fathi [http://www.ucv.ve/cifi/16%5CArticuloh.htm Recent Advances in Gold Metallurgy] {{webarchive|url=https://web.archive.org/web/20080330234816/http://www.ucv.ve/cifi/16%5CArticuloh.htm |date=2008-03-30}}</ref><ref name="Gray"/>

By 1891, Nebraska pharmacist [[Gilbert S. Peyton]] had refined the process at his [[Mercur, Utah|Mercur Mine]] in Utah, "the first mining plant in the United States to make a commercial success of the cyanide process on gold ores."<ref>{{cite book |title=The alumni quarterly and fortnightly notes |author=<!--Staff writer(s); no by-line.--> |date=January 1, 1921 |publisher=University of Illinois |url=https://books.google.com/books?id=HGDnAAAAMAAJ&q=Gilbert+Peyton+cyanide&pg=RA1-PA102 |access-date=May 1, 2016}}</ref><ref>{{cite web |title=Mercur, UT |author=<!--Staff writer(s); no by-line.--> |url=http://silverstateghosttowns.com/mercurut.html |access-date=May 1, 2016}}</ref> In 1896, Bodländer confirmed that oxygen was necessary for the process, something that had been doubted by MacArthur, and discovered that [[hydrogen peroxide]] was formed as an intermediate.<ref name="Recent Advances in Gold Metallurgy"/>
Around 1900, the American metallurgist [[Charles Washington Merrill]] (1869–1956) and his engineer Thomas Bennett Crowe improved the treatment of the cyanide leachate, by using vacuum and zinc dust. Their process is the [[Merrill–Crowe process]].<ref>{{cite book |last=Adams |first=Mike D. |title=Advances in Gold Ore Processing |date=2005-12-02 |publisher=Elsevier |pages=XXXVII–XLII |isbn=978-0-444-51730-2 |issn=0167-4528}}</ref>