28ir Annhjses of Booh. [Mxt^ 



Tnhich he suggested the name oi flnorine. This hypothesis was 

 adopted hy Sir H. Davy; and the object of the present paper is to 

 state the facts which can be brought forward in its support. 



Liquid fluoric acid was first obtained pure by Gay-Lussac and 

 Thenard. Jt is procured by heating concentrated sulphuric acid 

 and fluor spar, in retorts of silver or lead, and receiving the pro- 

 ducts in receivers of the same metals artificially cooled. It is a 

 very active substance, and requires to be examined with great 

 caution. Davy considers it as pure acid without any water. Its 

 specific gravity is 10G09. When mixed with water a great deal 

 of heat is evolved, and if the water be cautiously added, the spe- 

 cific gravity increases to 1*25. 



Fluoboric acid is a gas which may be obtained by heating in a 

 glass reton a mixture of fluor spar, boracic acid, and sulphuric 

 acid. Its specific gravity is 2-370. It forms a solid volatile salt 

 will) its own bulk of ammoniacal gas. 



According to the hypothesis of Ampere and Davy, fluoric acid 

 is a compound of fluorine and hydrogen; silicated fluoric acid, of 

 fluorine and silicon; and fluoboric acid, of fluorine and boron. 

 Fluor spar is a compound of fluorine and calcium ; and so of the 

 other compounds. The evidence brought forward by Sir H. Davy 

 in favour of this hypothesis is as follows : 1. Liquid fluoric acid !eis 

 go no water when combined with ammonia, as is the case with sul- 

 phuric, nitric, phosphoric, and all the acids containing oxygen. 

 2. When fluate of ammonia and potassium are heated, fluate of 

 potash is formed, and ammoniacal gas and hydrogen emitted in the 

 proportion of two measures of the first to one measure of the 

 second. This favours the notion that fluate of potash is a com- 

 pound of fluorine and potassium ; the hydrogen being produced by 

 tlie decomposition of the fluoric acid. Potassium when heated 

 with sal ammoniac gives a similar result. 3, When galvanic elec- 

 tricity is made to act upon liquid fluoric acid, the platinum wire at 

 the positive pole is corroded, and deposites a chocolate pouder, 

 while hydrogen only is given out at the negative pole. Now if it 

 had contained any other inflam.mable basis besides hydrogen, ana- 

 logy would lead us to expect that it would have been given out 

 along with the hydrogen; but this experiment was too imperfectly 

 made to be considered as conclusive. 



Tliese analogies led Sir H. Davy to endeavour to separate fluorine 

 from the fluates, by heating them in chlorine or oxygen ; but all 

 his attempts failed. In glass vessels the glass was violently acted 

 upon, and silicated fluoric gas and oxygen evolved. In platinum 

 vessels that n^ctal was acted on, and a red powder formed. Nor 

 u'as the attempt to decompose liquid fluoric acid by passing it along 

 chlorine through red hot tubes more successful. 



These experiments are fur from demonstiating the truth of the 

 hypothesis of Ampere and Davy ; though analogy is certainly in its 

 favour. 



14. Catalogue of North Polar Distances of eighty-four pria- 



