1
w hot i the we? ALTON BANKS Southwest Texas State University San MB~COS, TX 78666 Fluorine Symbol: F Atomic number: 9 Atomic weight: 19.00 Melting point: 53.6 K Boiling point: 85.1 K bnsity: 0.0017 glcm3 Fluorine. a vale vellow eas. is a relativelv ahundant ele- ment, being 13th in abunianhe in the e a r t h crust. While the element was obtained in a oure form in 1886. com~outIds of fluorine have been known'for many years. he earliest report of a fluorine compound is credited to Georgius Agric- ola who, in 1529, described the use of calcium fluoride as a flux. As early as 1670 H. Schwandhard reported that the vapors arising from the reaction of CaFz with a strong acid etched glass. Fluorine occurs naturally in the compounds fluorite, CaF2, cryolite, Na3AlF6, and fluorapatite, CadPOdaF. The name fluorine (le fluore) was suggested to Sir Hum- phrey Davy by A. Ampere in 1812 to reflect the similarity to the name for chlorine (le chlore). Davy bad-only two years earlier-announced proof of the elementary nature of chlo- rine to the Royal Society. One is tempted to muse about whether the only liquid of the halogens-hromine-would perhaps have been moreaptly named fluorine (Latin: fluerp, to flow) had it been discovered earlier. (Elemental hromine was discovered in 1826). Asan aside, G. G. Stokes coined the term fluorescence in 1852 todescribe the light emitted when calcium fluoride, also known as fluorspar, is heated. Fluorine is known to form compounds with every element except helium, argon, and neon. Indeed the reactions of fluorine with many suhstances-ceramics, carbon, and wa- ter-are accompanied by flames. The reactivity of the ele- ment prevented its isolation until June 1886. Many noted scientists-Davy, Scheele, Gay-Lussac, Lavoisier, and Thhard-tried to obtain the element but were unable to do so. Moisson successfully isolated the element by electrolysis of potassium fluoride dissolved in anhydrous HF-a method still in use. In 1906 Moisson was awarded the Nobel Prize for Chemistry for his work in isolating fluorine. In 1928 CCbF? was first svntheaized. and the use of . .- chlorofluorocarbo& as refrigerants prolif&ated following a patent in 1930. Other chlorofluorocarbons for example, CClaF, have been used as aerosol propellants. Work by Row- land and Molina that indicates a deleterious interaction of these compounds with ozone will certainly affect the future use of these compounds in this regard. In 1802 D. P. Mori- chini found fluoAde in fossil i v o i a n d teeth. Following the work of H. T. Dean in the early 19303s, fluoride salts (SnF2 and NaF) were introduced in toothpastes to harden teeth. The hydroxyapatite (Caa(POa)sOH) in teeth is replaced par- tially by the fluoro analogue, Cas(P04)3F. In 1938 a famous serendipity resulted in the "discovery" of polytetrafiuor- oethvene hv R. J. Plunkett. and Teflon made a Dermanent - ~ - ~ ~ imphnt onsociety-from frying pans to razor'blades. In 1940 fluorine was used to make UF6. Uranium hexafluoride sublimes readily, and was useful in the production of the atomic bomb. Sulfur hexafluoride is another im~ortant com- pound of fluorine and is used as an insulatinggas in high- voltage generators and switching gear. Hydrofluoric acid found its first commercial use in chlorofluorocarbon produc- tion and remains useful today in etching glass and frosting light bulbs. While these "synthetic" compounds of fluorine are important, it should he noted that the uses of the natu- rally occurring compounds are equally significant. Cryolite is used as the solvent in the Hall process for aluminum production, and fluorite-the most abundant of fluorine's three naturally occurring compounds-is used in iron metal- lurgy to reduce the slag viscosity in blast furnaces. Some of these applications are shown on "The Periodic Table Videodisc" in frames 36411-36422. General References "KC? oiscauere.: Exploring the Properties of the Chemical Elemmu": JCE: Softwarn McGrou-Hi11 Concise Encyciopadia of Science & Teehnoiogy; Parker, 6.. Ed.: McGrsw- Hill: New York, 1964:pp733134. Rowland, F.S.; Moiina, M.J.Reu. Geophys. SpocePhys. 1975,13(1), 1. Greenwood, N. N.; Earnrhaw, A. Chemistry of rheElemenrs: Pergamon. New York, 1964: "" 0.,-02" "p Roberta. Royaton M. Serendipity in Science; Wiley: New York, 1989: pp 187.190, Banks. A. J. "The Periodic Table Videodisc": JCE: Software 1989, Spcisl Isrue 1 Volume 67 Number 5 May 1990 373
