Michael Faraday's Failure with Fluorine

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Worked for Fluorine...

Professor Frank James, a world-leading expert on all things Faraday, delves into the Royal Institution Archives to reveal one of the very few failures of the great scientist.

From 1834 to 1835 Faraday was seeking to isolate the element Fluorine through the electro-chemical techniques used by Humphry Davy to isolate Sodium and Potassium (also at the Ri) in 1807.

Faraday’s kept a meticulous set of laboratory notes and paragraph 1477 begins with the promising phrase "Worked for fluorine".  However, his attempt to disassociate fluorine from molten lead fluoride (PbF2) – itself a very dangerous substance – was never successful due to the extreme reactivity of Fluorine. On release it reacted almost immediately with the oxygen in the air and could not be isolated.

The problem was only solved around fifty years later by the French Chemist Henri Mossain in 1886, a feat for which he received the Nobel Prize. 




Professor Frank James
Royal Institution, London
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The Royal Institution

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These are some of Faraday's objects that we've got on display in our collections. I'm interested in fluorine, because it represents one of the very few failures that Michael Faraday-- who worked in their Royal Institution, in the early part of the 19th century, made. In 1834 and 1835 he sought to isolate fluorine using the sorts of electro-chemical techniques that Davy used to isolate sodium potassium a generation or so before.

Faraday was an extraordinary meticulous worker. He kept a very detailed set of laboratory notes which ultimately ran to just over 16,000 paragraphs, that he numbered.

Fluorine is an extraordinarily reactive substance. It was first discovered-- well, the mineral which contains fluorine was first discovered in late 18th century. And people sought to try and isolate fluorine for the following 50 years. And in 1834 and 1835, Faraday spent a huge amount of time trying to isolate fluorine for the first time.

This is his entry for the 10th of February, 1834, paragraph 1477, starting with the wonderful line, "Worked for fluorine. Used a small strong platina vessel, like a little crucible, and having made a tube of platina soldered by gold, soldered it onto the former. Adjusted a thick, plat wire, P, so as to go into it. Touching nowhere, but dipping into fused fluoride of lead, which was kept in that state within by the heat of a spirit lamp without."

And what Faraday basically honed in on, as a method to try and isolate fluorine, was to heat up lead fluoride. And it's really surprising that when he got molten lead fluoride he didn't die as a consequence, as they are both really nasty materials. And then use electrolysis to try and dissociate the fluorine out of the compound. So here you have this spirit lamp down there taking off electric current-- positive pole there, negative pole there,

But the problem with fluorine is it's such a reactive substance. As soon as it was liberated it would react with another gas, like oxygen, for example. And so Faraday never ever got pure fluorine. And indeed, it was such a difficult problem that it took another 50 years before Henri Moissan, a French chemist, in 1886 isolated fluorine for the first time. And for that he won the Nobel Prize in the early 20th century.


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