A process invented in 1889 by Ludwig Mond (1838–1909) for extracting and purifying nickel. The process was developed after Mond noticed that nickel valves in a chemical manufacturing process became corroded by carbon monoxide. He discovered a new compound called nickel carbonyl Ni(CO)₄ and that pure nickel could be obtained by reaction with carbon monoxide at 50^ºC, and that the new compound decomposes on further heating to around 200^ºC.