The Tiger of Chemistry Fluorine - the gas of Lucifer .

Warning - Under no circumstances should anyone but an expert experimental chemist attempt to replicate the work of Gore or Moissan. Elemental fluorine is extremely dangerous and many fatalities resulted from early production methods.

The element fluorine is a pale greenish-yellow gas. It occures naturally within some fluorite crystals. Dark violet fluorite from Wölsendorf in Bavaria is called antozonite because the smell of ozone is apparent when crystals are fractured or crushed. Violet crystals from Quincie, dep. Rhône, France are similar. In both cases the ozone is generated by the release of free fluorine from the crystal lattice. The fluorine reacts with water vapour in the air, forming hydrogen fluoride and ozone. A nasty combination.

The extreme difficulties in isolating fluorine can be gathered from this account :

Humphrey Davy of England: poisoned, recovered.

George and Thomas Knox of Ireland: both poisoned, one bedridden 3 years, recovered.

P. Louyet of Belgium: poisoned, died.

Jerome Nickels of Nancy, France: poisoned, died.

George Gore of England: fluorine / hydrogen explosion, narrowly escaped injury.

Henri Moissan of France: poisoned several times, success, but shortened lifespan.

The isolation of fluorine is credited to Moissan in 1886, accounts below. However, the endevours of George Gore in 1869 are worthy of reflection.

A skilled electrochemist, Gore appears to have been a big-bang experimentalist. His preparation of explosive allotropes (see explosive antimony), is an example of his interests. He would have been fully aware of the dangers involved with fluorine.

Specifically, he would be know that the reaction of, as yet unseen, fluorine with hydrogen would be highly explosive and spontaneous. The properties of fluorine had been predicted from its position on the periodic table, at the top of the halogens in a series of increasing reactivity. Chlorine, the less reactive sister, when mixed with hydrogen, explodes with extreme violence if the mixture is exposed to light. Gore would have known that, at all costs, the gaseous products of his electrolysis, fluorine and hydrogen, had to be kept apart. Accounts of Gores electrolysis apparatus exploding because of an accidental leak are not credible. Gore arranged that first gaseous meeting of these extreme elements... He liked explosions!

Gore had no difficulty in producing fluorine, using a molten silver fluoride electrolyte, the problem was its collection and containment. Fluorine chemically reacts with just about everything, usually very vigorously. He fashioned collection vials from platinum, palladium and gold. All were destroyed. Partial success was achieved using a carbon vial, which the fluorine attacked relatively slowly. Gore was apparently able to transfer the gas into a stoppered vial carved from a fluorite crystal. Then he arranged its meeting with the hydrogen he`d collected from the cathode. Quite apart from the violence of the explosion, Gore was in an extremely perilous situation. The hydrogen fluoride gas produced by the explosion could easily have poisoned him.

Moissan

This french chemist succeeded in the preparation, isolation and observation of the properties of fluorine gas... also without being killed. Moissans work also included spectacular electric arc methods of synthetic diamond production.

An account of his experiments of 1886:

"I obtained the fluorine from a fluorine compound that had been added to a mineral having a low melting point and in which the fluorine compound dissolved readily. The use of electricity produced the fluorine at the positive terminal. Difficulty was experienced in getting any material for that terminal that would resist the chemical action of the gas. After some failures, and four interruptions of work caused by severe poisoning, the following arrangement of apparatus proved fairly satisfactory. Two electrodes were made from an alloy of platinum and iridium. These were sealed into a platinum U-tube closed with caps made from the mineral fluorspar, the caps being covered with a layer of gum-lac. The U-tube was chilled to 10 degrees below zero Fahrenheit to reduce the rate of the action of the fluorine on the platinum. The first test made with the gas was to bring it in contact with the element silicon. There was an immediate burst of flame, a gaseous product being formed."

Ferdinand Frederic Henri Moissan died, aged 55, in 1907; a year after recieving the Nobel prize for chemistry. Here are a couple of interesting accounts of fluorine preparation & properties which detail Moissan`s apparatus -

From "A Text-Book of Inorganic Chemistry" by JR Partington, 1946 (large graphics files)

From "Modern Inorganic Chemistry" by JW Mellor, 1934 (large graphics files)

My own experience with fluorine has been solely with its compounds. In particular, natural calcium fluoride crystals (fluorite or fluorspar). Also hydrofluoric acid, during a highly ill-advised "experiment" conducted in the clean room of a semiconductor manufacturer unwise enough to employ me.... The glass and quartz-ware used in diffusion furnaces must be kept scrupulously clean to avoid contamination of the silicon wafers being processed. Consequently it is periodically bathed in a mixture of hydrofluoric and nitric acids. Full protection clothing was donned over normal clean room eyes-only-exposed garb, and a large silicon wafer (complete with defective 4Mb DRAMs) was "carefully" thrown into the acid bath. Nothing happened for about twenty seconds, as the HF attacked the silicon, heating up the wafer until a runaway reaction started. The acid bath then erupted into a frightening boiling maelstrom, with the violent evolution of copious amounts of red and brown fumes of nitrogen oxides. The complete destruction of high technology by the tiger of chemistry.

Splendid.

Note - Acid ready for disposal was used, production was not compromised, and no animals were endangered.