Aluminum: Common Metal, Uncommon Past

Lockheed lounge by Marc Newson

Lockheed lounge by Marc Newson

The honor of first producing elemental aluminum went instead to Hans Christian Ørsted, a professor at the University of Copenhagen, who in 1825 produced a tiny amount of the metal by rapidly heating aluminum chloride (AlCl3) with potassium amalgam (an alloy of potassium and mercury) and then distilling off the mercury. Unfortunately, Ørsted's process produced too little aluminum to perform even the most basic analysis, and his experiment was difficult to reproduce. The German chemist Friedrich Wöhler tried again in 1827, one year before he pioneered the field of organic chemistry by synthesizing urea. While his aluminum experiment did not produce the lump metal he desired, he did obtain an impure aluminum powder after substituting metallic potassium for Ørsted's potassium amalgam. And there the matter rested until 1845, when Wöhler produced "gray metallic powder . . . [with] small tin-white globules [of aluminum], some as large as pins' heads," by heating potassium and aluminum chloride together in a closed system, thereby excluding the moisture that had been diverting aluminum into aluminum hydroxide (Al(OH)3).

To Electrolysis and Back Again

By the mid-1850s battery technology had improved in output and reliability to the point that the first electrolytic production of aluminum was possible. Aided by this advance, and foreshadowing Hall's and Héroult's twinned, simultaneous discovery 32 years later, the first electrolysis of aluminum was also developed independently by two parties.

The first researcher to claim to produce elemental aluminum by electrolysis was the German Robert Wilhelm von Bunsen, who by coincidence had taken Wöhler's place as a chemistry teacher at the Higher Polytechnic School at Kassel in 1836. A man of wide-ranging interests, Bunsen ultimately became famous for developing the spectroscope and for the use of iron-oxide hydrate as an antidote to arsenic poisoning. (Curiously, he did not invent the burner that carries his name; that was the work of his assistant Peter Desaga, who improved on a design by Michael Faraday.) In 1841 Bunsen improved on an 1839 battery design by William Robert Grove, who a few years later also produced the first hydrogen-oxygen fuel cell. Bunsen lowered the cost of Grove's battery by replacing the platinum cathode with a more cost-effective carbon one inside the battery itself. With these batteries he started experimenting with electrolysis, producing pure chromium, magnesium, manganese, sodium, barium, calcium, and lithium, in addition to very small amounts of what he believed to be aluminum in 1854. But he then moved on to other areas of interest, publishing his important paper on emission spectroscopy in 1860.

The second person to experimentally reduce aluminum ions to metal by electrolysis was the Antilles-born Frenchman Henri Sainte-Claire Deville, who presented his findings on electrolytic production to the French Académie des Sciences in 1854, a week after Bunsen published his results. His work attracted the attention of Napoléon III, then titled "Emperor of the French," who was interested in the metal as a source of military armor. With Napoléon III's mandate, Deville quickly realized that the cost of zinc for anodes in the Bunsen cells he used was too high to efficiently produce aluminum through electrolysis. Instead he lowered the cost by returning to chemical methods, replacing Wöhler's potassium with sodium—that is, AlCl3 + 3Na → Al + 3NaCl. Through this process he was able to obtain enough aluminum to produce marble-sized blobs. In 1855 he displayed an ingot of comparatively pure aluminum at the World's Fair in Paris, to great popular interest. Because the Deville process was deemed "good enough," most scientists then set aside experiments on electrolytic production of aluminum.

Deville made good use of Napoléon III's money over the next few years, founding an aluminum production facility in Paris in 1856 before moving it to Nanterre in 1857. In 1858 he patented a method for making the extraction of alumina (Al2O3) from mineral bauxite more cost-effective. These efforts introduced aluminum to the world by lowering its price to a level that allowed ordinary people to afford aluminum jewelry. (The 1859 price for a pound of aluminum was around $17, about the same as silver.) His 1859 book, De l'Aluminium, ses Propriétés, sa Fabrication et ses Applications (On aluminum, its properties, its production, and its applications), was the first to describe the metal fully, sparking the research that would lead to Hall's and Héroult's famous discoveries.