fluorin

from The Century Dictionary.

• noun Chemical symbol, F; atomic weight, 19. A gaseous element, not known in a free state, since its isolation is a matter of great difficulty and of some doubt.
• noun After several abortive or doubtfully successful attempts by various chemists to isolate the element fluorin this result was finally attained by Moissan in 1886. He submitted to electrolysis anhydrous hydrofluoric acid in which a little potassium-hydrogen fluoride had been dissolved, using a specially constructed apparatus of platinum alloyed with iridium. Fluorin so obtained is a gas of pale greenish-yellow color, with a strongly irritant and penetrating odor, liquefiable at about —185° C. under atmospheric pressure, and intensely active in its chemical relations to other substances. It combines even in darkness with hydrogen with violent detonation; silicon, boron, arsenic, antimony, sulphur, and iodine take fire spotaneously in the gas; and it decomposes water with liberation of oxygen in the form of ozone. With oxygen itself fluorin will not combine.