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Most metals are purified by melting or electrolysis. Nickel has an unusual route: turn it into a gas at about 60 °C, carry it away from everything else, then heat the gas to drop pure nickel. Ludwig Mond found that route by chasing a problem with leaking valves. This post covers his life, the discovery, a worked example on nickel carbonyl, and what students can take from his way of working.
Who was Ludwig Mond?
The chemist F. G. Donnan gave a lecture on Mond at the Royal Institution in 1939, a hundred years after his birth, published by the Institute of Chemistry and digitised by the Wellcome Library. It records that Mond was born on 7 March 1839 in Cassel (Kassel), Germany, studied under Hermann Kolbe at Marburg from 1855 and then for three years under Robert Bunsen at Heidelberg. He moved to England in 1862 to work a process he had patented for recovering sulphur from alkali waste. With John Brunner he founded the Brunner Mond works at Winnington, which began making soda by the ammonia-soda process in 1873. He died in 1909.
How did a leaking valve lead to a discovery?
Donnan describes the chain. Mond was developing a process to recover chlorine from the ammonia-soda works, and chose nickel valves because nickel resisted hot ammonium chloride. In the plant the valves leaked, and Carl Langer, Mond's assistant from 1884, found them coated with black carbon. The cause was a small amount of carbon monoxide in the lime-kiln gas: hot carbon monoxide over nickel gives carbon and carbon dioxide.
In a later experiment, Donnan says, Langer let the heated nickel cool while carbon monoxide still flowed, and the pale blue flame where the waste gas was burned turned greenish-yellow. The 1890 paper says the flame "became highly luminous" and that heating the tube left a mirror of nickel. A nickel compound was escaping as a gas.
What did the 1890 paper report?
Mond, Langer and Friedrich Quincke published Action of carbon monoxide on nickel in 1890, readable in a digitised volume of the Journal of the Chemical Society. They report that finely divided nickel absorbs carbon monoxide once cooled to about 100 °C, giving a volatile compound. Heated above 150 °C it decomposes, and at 180 °C it deposits nickel free of carbon. One volume of the vapour gives four volumes of carbon monoxide, which led them to the formula Ni(CO)₄. The liquid boils at 43 °C and solidifies at −25 °C, and its vapour exploded violently at 60 °C. Cobalt, iron, copper and platinum gave no such compound, so carbon monoxide could separate nickel from cobalt.
How did it become an industry?
Donnan describes a pilot plant at Smethwick in 1892, nickel ore mines near Sudbury in Canada, and a refinery at Clydach in South Wales. Oxide was reduced to metal at 350 to 450 °C, turned into carbonyl at about 60 °C, and decomposed at 180 °C onto nickel pellets, with the carbon monoxide recycled. By 1910 Clydach was selling 3,000 tons of 99.9 per cent nickel a year.
The NCERT Class 12 chapter on coordination compounds gives Ni(CO)₄ as tetrahedral and notes that metals can be purified by forming and then decomposing their coordination compounds.
Worked example: nickel carbonyl by the numbers
Molar masses: Ni = 58.69, C = 12.01, O = 16.00 g/mol.
Molar mass. Ni(CO)₄ = 58.69 + 4(28.01) = 170.73 g/mol.
Per cent nickel. 58.69 / 170.73 × 100 = 34.38 per cent. The 1890 paper found 33.35 and 33.37 per cent, a little low, which the authors put down to carbon monoxide dissolved in the liquid.
Gas volumes. Ni(CO)₄(g) → Ni(s) + 4CO(g). At the same temperature and pressure, 100 cm³ of vapour gives 400 cm³ of CO. The paper measured 405.9 and 400.5 cm³.
Carbon monoxide per kilogram of nickel. 1000 / 58.69 = 17.04 mol Ni needs 4 × 17.04 = 68.2 mol CO, which is 68.2 × 28.01 = 1,910 g, about 1.9 kg. It is released again in the decomposer, which is why recycling it matters.
What mistakes do students make with metal carbonyls?
Writing the wrong oxidation state. In Ni(CO)₄ nickel is zero, as the NCERT name tetracarbonylnickel(0) shows.
Mixing up refining and extraction. The carbonyl step purifies nickel that has already been reduced from its ore.
Using four CO by mass instead of by moles in gas-volume questions.
The JEE (Main) 2026 syllabus lists coordination compounds in Unit 12, including their importance in the extraction of metals; check your year's syllabus. Our posts on naming coordination compounds and Alfred Werner cover the theory. If bonding in carbonyls is a concept gap, the Fermi Concept Library has every concept in physics, chemistry, biology, mathematics and computing, each with its own lesson and its place in the map.
What can a student take from how he worked?
Chase the anomaly. A leaking valve and a flame changing colour were clues, not nuisances.
Measure to confirm. Gas volumes and nickel percentages fixed the formula.
Scale up patiently. The step from a laboratory tube to Clydach took about a decade of pilot work.
Share the credit. Langer's observations were central, and his name is on the paper.
Next step: work out the volume of carbon monoxide at 0 °C and 1 bar (22.7 L/mol) released when 1 kg of nickel is deposited.
