JANUARY 1 6, 1902J 



NATURE 



253 



apparently colourless gas with a penetrating disagreeable 

 odour resembling that of hypochlorous acid. It was 

 endowed with exceedingly active chemical properties. 

 Hydrogen combined with it with explosive violence ; 

 most of the non-metals burnt in it, while the metals were 

 less vigorously attacked. All organic substances were 

 immediately decomposed. 



Three hypotheses suggested themselves as to the 

 nature of the gas. First, that it was a mixture of ozone 

 and hydrofluoric acid. No such mixture, however, was 

 found to exhibit the properties already described. 

 Secondly, that it was a perriuoride of hydrogen ; and 

 thirdly, that it was the wished-for fluorine itself. This 

 last point was settled by studying the 

 action of water on the gas. 



In the first case 



2HF„ + H„0 = 4HF + O. 



have been studied very completely ; as also the fluoride 

 of arsenic (ASF3) and the tetrafluonde of carbon. 



In the case of the metals the action is not so energetic, 

 the solid fluoride formed on the surface of the metal 

 preventing further combination. 



The metals of the alkalis and alkaline earths take fire 

 in the gas ; lead combines slowly. Magnesium, alumi- 

 nium, nickel and silver on slightly heating burn brightly 

 on contact with the gas. Manganese heated in a current 

 of fluorine yields a sesquifluoride, Mn.,F„ ; this on further 

 heating splits up into the difluoride, MnFo, and liberates 

 fluorine. Gold and platinum are unattacked in the cold, 

 but combine at a dull red heat ; the platinum fluoride has 



In the second 

 F„ -t- H„0 



2HF -h O. 



By measuring the volume of o.xygen 

 liberated and titrating the quantity of 

 hydrofluoric acid formed, Moissan 

 was able to decide in favour of the 

 third hypothesis : the gas must be 

 fluorine. 



• The value of this work was at once 

 recognised. Moissan was rewarded 

 with the chair of " Toxicologie" at 

 the " Hcole de Pharmacie." "J'avais 

 done,'' he says, in a letter to the pre- 

 sent writer, "tres jeune un labora- 

 toire, et un preparateur ; quelques 

 el&ves vinrent se grouper autour de 

 moi, et toute mon ambition fut 

 satisfaite." 



His faculties now had free play ; he 

 was able to work on a wider basis, 

 and became one of the most prolific 

 contributors to the Coiuptes rendus. 



The isolation of fluorine was 

 naturally followed by a systematic ex- 

 amination of its properties and deriv- 

 atives. This work is still being 

 carried on ; recently, however, IVI. 

 Moissan collected and published in 

 one volume 1 (he results he has 

 obtained. They are all interesting, 

 and some of great theoretical import- 

 ance. 



He found it more convenient and 

 less costly to carry out the electrolysis 

 of the anhydrous acid in a U-tube 

 made of copper immersed in a mixture of acetone and 

 solid carbonic acid, i.e., at a temperature of - 50' C. The 

 electrodes as before were of platinum isolated from the 

 apparatus by means of stoppers of fluorspar. The 

 fluorine thus obtained was purified by passing it through 

 a spiral cooled to - 50 C, and then through a horizontal 

 tube containing fragments of sodium fluoride ; thus the 

 hydrofluoric acid was removed. Perfectly dry fluorine 

 which has been passed through a spiral immersed in 

 liquid air, to solidify any traces of hydrofluoric acid 

 remaining, has no action on dry glass even at the 

 ordinary temperature. 



It possesses a slightly greenish-yellow colour, paler than 

 that of chlorine. It unites with greater or less violence 

 with all the non-metals save oxygen, nitrogen and argon ; 

 the compounds being sometimes gaseous, and sometimes 

 solid. The tri-, penta- and oxy-fluorides of phosphorus 



1 "Le Fluor et ses composes." Par Henri Moissan. (G. Steinlieil, 

 Paris, 1900.) 



NO. I 68 I, VOL. 65] 



Iab:>ralory. 



the formula PtF4 ; at a higher temperature the gold and 

 platinum compounds are decomposed into fluorine and 

 the respective metal. 



Organic compounds rich in hydrogen are violently 

 attacked by fluorine, and totally decomposed into hydro- 

 fluoric acid, and fluorides of carbon. Organic acids are 

 attacked more slowly ; amines and alkaloids are rapidly 

 burnt up or decomposed into volatile products. 



liy indirect reactions involving the use of the fluorides 

 of sflver and zinc, Moissan and Meslans have been able 

 to prepare and examine the properties of methyl, ethyl 

 and isobutyl fluorides, fluoroform, acetyl fluoride, and a 

 few other derivatives. 



The latest determination gives the atomic weight of 

 the element as 1905. 



A general survey of its chemical and physical proper- 

 ties confirms the surmises of .Ampere and Davy : fluorine 

 falls naturally into place at the head of the so-called 

 "natural group' chlorine, bromine, and iodine. 



