Stephen F. Austin State University SFA ScholarWorks Faculty Publications Chemistry and Biochemistry 1983 Fluorine Richard H. Langley Stephen F Austin State University, [email protected] Larry Welch University of Wisconsin-River Falls Follow this and additional works at: https://scholarworks.sfasu.edu/chemistry_facultypubs Part of the Chemistry Commons Tell us how this article helped you. Repository Citation Langley, Richard H. and Welch, Larry, "Fluorine" (1983). Faculty Publications. 35. https://scholarworks.sfasu.edu/chemistry_facultypubs/35 This Article is brought to you for free and open access by the Chemistry and Biochemistry at SFA ScholarWorks. It has been accepted for inclusion in Faculty Publications by an authorized administrator of SFA ScholarWorks. For more information, please contact [email protected]. edited by DARRELLH. BEACH The Culver Academies chemical of the month Culvw. Indiana 46511 Fluorine probable reason for this failure was that any fluorine formed would immediately react with anything it came in contact with Rlchard H. Langley at the temperature at which fluorite is a liquid. During this Box 13006, SFA Stallon work Daw was poisoned hv hvdroaen fluoride and suffered Staphen F. Auslln State Unlrenlty .. Nacogdoche%TX 75962 from its effects for many years. During most of the remainder of the nineteenth century Larry Wekh several attempts to isolate fluorine were made. The results of Unlversny 01 Wllconeln-Rlrer Falls these efforts were the early deaths of George Knox, P. Louyet, Rlver Falls, WI 54022 and JQr8meNickles, and a close brush with death for Thomas Considerine the lone time in which fluorine comoounds Knox (George's brother). have heen used it seems rather surprising that it was not iso- In 1885 the French scientist Edmond FrBmy, one of lated as an element until 18%. This lone-. delav wa9 not due to Louyet's assistants, took up the challenge of isolating fluorine. lack of effort, but to the reactivity of fluorine and the hazards After repeating Davy's work with no success, he decided to try of working with it and many of its compounds. the electrolysis of hydrogen fluoride since this could he done at a much lower temoerature than the electrolvsis of calcium ~ " Hlslory ( 1-3) fluoride. His early results showed that oxygen appeared at the Georgius Agricola in 1529 discussed the use of a mineral, anode instead of fluorine. This was anoarentlv due to the fluores, to reduce the melting point of various ores. This presence of water in the hydrogen fluoride. ~rkmythen set lowering of the melting point saved much time and fuel during about oreoarine anhvdrous hvdroeen fluoride. He succeeded the smelting process. The name fluores was from the Latin, in thistask, hui a new prohl&n arose: anhydrous hydrogen fluere (to flow), alluding to its ability to help the ore toliquify fluoride did not conduct electricitv... so it could not he elec- or flow. The name was later chanaed to fluorsoar, and then trolyzed. to fluorite so that its name would r,.mform to standard mineral One of FrBmy's students, Ferdinand Fr6dBric Henri Mois- terminolorv. Fluorite is still brinr med in the stre1 makine:- san, continued the work. After several false starts he was able process. m he composition of fluorite is CaF2. to isolate a pale yellow-green gas on June 26,1886. At this time In 1670 the use of another fluorine compound was initiated. Moissan tried the electrolysis of anhydrous hydrogen fluoride Heinrich Schwanhard of Nuremburg discovered that when obtained by distillation from a potagsium bifluoride melt. This a strong acid was added to fluorite, a gas evolved that etched work was carried out using platinum or platinum alloy appa- the glasses he was wearing. Since he was a member of a famous ratus. However, even the inert platinum was attacked so that family of glass cutters, he quickly realized the commercial the weight loss of the platinum was greater than the wt*tght potential of this process, and became very successful pro- of fluurtne produced. When Moisssn attempted to repeat t hts ducing art figures by etching glass. This process was kept a experiment in front of a committee appninted by the Araili.. trade secret for manv vears. mir des Sciences, he was unw~ce.wfuI.Ji~~llowine this ht'dis- Carl Scheele, a ~weiishchemist, in 1780 determined that covered that the reasonwhy his original experiment worked the gas generated by Schwanhard's process was an acid. He was that his hydrogen fluoride had been contaminated by a called this acid "fluoric acid." Scheele had a habit of smelling little potassium fluoride. He had redistilled the hydrogen and tasting all of the new chemicals that he isolated. This fluoride before the demonstration for the committee, and the habit, no doubt, contributed to his early death. imnuritv was removed so it would not conduct electricitv. In 1810. chlorine was discovered. It was the first haloeen to bloissan continued his work with fluorine, and improved his techmnues. His successful work in isolatine elemental fluorine be isolated and recognized as an element. Chlorine was pre- -~~~ ~~ ~~ oared hv Sir Humohrv Daw hv oxidizine muriatic (hvdro- led to Lis receipt of the Nobel Prize in 1906. Ehloricjkid. ~~v~;henwenioitosh,#w that fluoric ari; was While it was now possible to prepare fluorine, it would be analogous to hydrochloric arid. And+ Amp&reand 1)avy then many years before it would be possible to routinely work with assumed that an element analogous tochlorine exiswd in this it in the laboratory or in industry. acid. They named the new thnent fluorine cfrum the root of fluorite). ~luoritewas determined to be calcium fluoride. The Preparatlon next step was to isolate this new element. The ohvious way to In 1899, Moissan modified his original method of prepa- isolate fluorine was by a method similiar to that used to isolate ration by substituting copper for the more expensive plati- chlorine. However, it was found that the acid, now called hy- num. Copper is attacked by fluorine also, however a coating drofluoric acid, could not he oxidized. This result would seem of copper (11) fluoride forms that protects the copper from obvious today because it is well known that fluorine is the most further attack. Over the years the electrdlyte has been modi- electronegative element, and therefore, the fluoride ion is the fied in various ways. The currentlv used comoosition has ao- most difficult to oxidize. proximalelv a 2:l &o of HF to KI.' (41. As thi electrolysis 411 At about this time it was found that compounds could he is operated, anhydrola hydrogen fluoride is aildt~ilto keep the hroken down by electricity. Davy was able to isolate several electrolyte composition ielaGvely constant. elements this u,ay, but when he attempted to product! fluorine During the first half of this century several chemists, most by th~!electrolysis of flunrite, he was unsuccessful. The notably Otto Ruff, attempted to find a reagent that could he used to produce elemental fluorine by a chemical reaction. The structure, propmies, and uses of a variety of chemicals are high They were only partially sucressful. While cwnpounds were lighted in mis mature which is aimdaf increasing me use of descriptive Chemistw. found that would drr~mp~~seto yield fluorine, all of these compounds required elemental fluorine in their synthesis. Volume 60 Number 9 September 1983 759 There is now a system that will produce elemental fluorine states. Examples of these are compounds containing species chemically. It is such as 0+2, Cu+4, Ag+E, and Au+? On the other hand, it does not stabilize low oxidation states, thus copper (I) fluoride UCls + 5 HF - UF. + 5 HCI disproportionates to copper (11) fluoride and copper. Another special property of fluorine is that it has been found to be able to form compounds with the noble gases. It is the only element that will react directly with a noble gas. In general, most of the chemical properties of fluorine re- semhle those of the other halogens. The major difference is This-~~~~ series~ ~ will orobablv not be commerciauv useful, but it is the enereetics involved. These enereetics are, in Dart, due to interesting to nbte thatafter somany years h is nowpossible thr elec& affinity of fluorine revin though it is lower than to produce fluorine chemically (5-8). that of chlorine), in Dart due to the low hond dissociation en- ergy of diatomic.flubrine, and in part due to the strengths of Occurance the bonds it forms with other elements. Bonds in fluorides are, Approximately 170 minerals are known that contain some in general, stronger than bonds in compounds containing other fluorine. However, only two of these, fluorite (Cadand ap- anions. atite (Cas(P04)~(F,0H,CI~/2C03),occur widely. Another mineral, cryolite (NasAIFs), is used in aluminum refining and Uses so is very important, but it is only found in four or five places The first time elemental fluorine was used on a large scale in the world. Only one place, Ivigtut, Greenland, has any sig- was during World War 11. A method was needed for separating nificant amounts. In many of the minerals containing fluorine, fissionable 2"5U from the more abundant It was found the fluoride ion replaces the hydroxide ion, therefore all hy- that uranium (IV) oxide, from uranium ores, could be reacted droxide species may contain \,a~ingamounts of fluorine. This with anhydrous hydrogen fluoride to produce uranium (IV) re~lacementis due tn the similarity in si7~and charge between fluoride which could, in turn, be converted to the hexafluoride these two ions. when reacted with fluorine gas. When uranium (VI) fluoride Fluorite is a verv widesoread mineral, and it is mined in is heated to 56'C it sublimes, and the 2JsUFs and 2"UFfi can many places.