Adventures in Archive: Faraday and Fluorine

Telling stories from the Ri's Archive can mean highlighting failure as well as scientific success.

Back in December we filmed a series of videos asking people to pick their favourite element and explain the reasons behind their choice.

As head of the Ri's historic collections, we were expecting Professor Frank James to select one of the ten chemical elements isolated at the Royal Institution. His choice, however, pointed to failure and forgotten experiments. Opening up Michael Faraday's original notebooks he revealed one of the great scientists few failures - his attempts to isolate the extremely reactive element, Fluorine. 

The resulting video is (hopefully) the first in a series of short films exploring the Ri's remarkable archive by revealing personal documents, showcasing unique objects, and telling extradonary stories from the history of science and innovation.

Below, Professor James explains the historical efforts to isolate fluorine - from Humphry Davy to Henri Moissan.

Discovering Fluorine

Fluorine is the most reactive gas in the periodic table and it should, therefore, not be found surprising that it was not isolated until the late nineteenth century. Nevertheless, from early in that century it was understood that fluorine must exist as a separate chemical element and much effort was put into isolating it, particularly by Humphry Davy and Michael Faraday working in the laboratory of the Royal Institution.

Davy was appointed to the Royal Institution in 1801 after working at Thomas Beddoes’s Pneumatic Institution in Bristol where he had discovered the physiological effects of nitrous oxide – laughing gas. At the Royal Institution, Davy had access to the best equipped laboratory in England and one of the best in Europe.

Following the invention of the electric battery by Alessandro Volta at the end of the eighteenth century, the Royal Institution soon acquired an array of very powerful batteries, initially used for experimental demonstrations in the lecture theatre. However, in the autumn of 1807 Davy started using them to decompose chemical compounds, thus starting the science of electro-chemistry, a term that he coined. On 19 October 1807 Davy produced potassium for the first time by passing a strong electric current through potash. The same month he also isolated, using the same method, sodium and boron and the following year magnesium, calcium, strontium and barium.

Two years later he turned his attention to muriatic acid which was assumed, by Lavoisier’s definition of acidity, to contain oxygen. However, Davy was unable to decompose this electro-chemically and concluded that it was therefore a chemical element which he named chlorine because of its green colour. He also tried using this method on fluoric acid, which had been known as a compound since the eighteenth century. He persisted with his attempts and may well have succeeded since he produced some temporary damage to his fingers and eyes. He did enough to convince himself that an element, which he called fluorine following the suggestion of the French savant André-Marie Ampère, did exist, but did not continue his researches.

However, Davy’s successor at the Royal Institution, Faraday did return to the pursuit following his work on electro-chemistry in the early 1830s where, amongst other things he introduced terms such as electrode, cathode and ion into science. Faraday thought in February 1834 that he had isolated fluorine, and indeed announced that he had done so and would publish further details later. When he came to continue work, he realised that he had not actually isolated fluorine and despite considerable effort during 1834 and 1835 was unable to do so – a negative result that he published when he collected his papers together in a single volume.

The problem that neither Davy, nor Faraday, could overcome was to develop a container that would not react with fluorine. It was Henri Moissan’s idea, which he had towards the end of the nineteenth century, that the way to approach the problem was construct a container which was made of a material that already contained fluorine and would therefore not react with it. Using this insight Moissan was able to isolate fluorine and for this he won the Nobel Prize for Chemistry in 1906, just over a century after Davy had started his electro-chemical work.

Reacting Fluorine with Caesium

Dr Peter Wothers prepares for the 2012 Christmas Lectures by reacting the most reactive metal (Caesium) with the most reactive non-metal (Fluorine):

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