Two hundred years ago the word aluminum was used for the first time when a new metal was produced by the English chemist Sir Humphry Davy. Later work has shown that this metal was not pure, but rather an aluminum-iron alloy. This article commemorates the anniversary of aluminum production with a look back at the metal’s origins.
INTRODUCTION
In 1807 a new metal was named for the first time by the English chemist Humphry Davy. Or maybe it happened in 1808. because one can find both these years mentioned in the extensive literature on the history of this metal. The exact date does not matter so much any longer, and in any case we can now celebrate the bicentenary of aluminum, or aluminium.
Davy showed that alumina could be decomposed while fluid in an electric arc and its metal was then reduced to an Al-Fe alloy. However, he was unable to isolate the aluminum and that took another two decades of work by others. The metal derives its name from alumen, the Latin name for alum, a white mineral that had been used since ancient times for dyeing and tanning, among other things. Alumen is believed to originate from the Greek word for bitter, alydimos. Alum is a bitter substance that for a long time was used to stop bleeding. Chemically, alum is potassium aluminum sulphate, KAl(SO^sub 4^)^sub 2^.
Humphry Davy was born on 17 December 1778 in Cornwall in England. At the age of 19 he went to Bristol to study science. He became interested in chemistry after reading Antoine Lavoisier’s Traite Elementaire. He investigated gases and in 1800 published the results of his work in “Researches, Chemical and Philosophical.” This made his reputation and in 1801 he was hired as an assistant lecturer in chemistry at the Royal Institution in London, where he was a great success.
ELECTROCHEMISTRY
In 1800 the Italian scientist Alessandro Volta had introduced the first battery, which Davy used for what is now called electrolysis. He then tried passing current through molten compounds, and his persistence was rewarded when he was able to separate globules of pure metal by these means. His first successes came in 1807 with the separation of potassium from molten potash and of sodium from common salt (NaCl). He was able to isolate a series of substances for the first time, and calcium, strontium, barium, and magnesium were produced in 1808. He also studied the forces involved in these separations, inventing the new field of electrochemistry. Davy was then considered as one of Britain’s leading scientists and he was knighted in 1812.
ALUMINUM IS PRODUCED
In 1825 Hans Christian Ørsted, professor at the University of Copenhagen, first successfully isolated aluminum in a pure form by the reaction of potassium amalgam on anhydrous aluminum chloride, AlCl^sub 3^. As mentioned already, Humphry Davy had been unsuccessful at such attempts. The reason for this is that aluminum oxide (alumina) is so stable that it could not be reduced by the methods that were commonly used in those days. The reduction with carbon works well for many other metal oxides, but this is extremely difficult with alumina. The trick used by the Danish physician was to heat aluminum chloride together with metallic potassium.
The product was not particularly pure and the German scientist Friedrich Wöhler developed the method further two years later. He was the first to produce pure metallic aluminum by use of the same method. The aluminum was produced in the form of a grey powder, but the small amount was insufficient to establish the properties of the metal. Wöhler returned to the problem of isolating aluminum in 1845 and then 10-15 mg of metal globules were produced by passing AlCl^sub 3^ vapor over molten potassium. Some properties of the metal could then be reported, such as its density, malleability, and ductility. He also discovered the aluminum had a relatively low melting point. In 1855, ignorant of what Friedrich Wöhler had done ten years previously, a French chemist, Henri Etienne SainteClaire Deville succeeded in obtaining metallic aluminum, and ultimately he devised a method by which the metal could be prepared on a large scale with the aid of sodium. It took another three decades before Charles Martin Hall and Paul L.T. Héroult. independently of each other, invented the process of electrolysis of alumina in a cryolitic melt. And the rest, as they say, is history.
