FLUORINE. 261 



hydrogen with an element yet unknown — fluorine — or, in brief, that it 

 was not au oxygenated acid. 



Davy, who shared this view, sought at once to prove that hydrofluoric 

 acid contained no oxygen. For this purpose he neutralized the pure 

 acid with ammonia, and strongly heating the salt in an apparatus of 

 platinum, collected in the colder parts of the latter only the sublimed 

 tluohydrate of ammonia containing no trace of water. 



Let us repeat the experiment, but with an oxygenated acid; let 

 us take sulphuric acid and neutralize it with ammonia. We thus 

 obtain ammonium sulphate. If now we heat this salt in the same 

 platinum apparatus, it will fuse at about 140° C; then, at about 180°, 

 it will decompose into ammonia and the bisulphate, and the latter, at a 

 still higher temperature, will be transformed into volatile ammonium 

 bisulphite, nitrogen, and water. 



Thus, upon strongly heating ammonium sulphate there has been a 

 formation of water, and in this experiment of Bavy, when iDerformed 

 with an oxygenated iicid, the quantity of water collected is so great as 

 to be unquestionable. The fluohydrate of ammonia, like the chlor- 

 hydrate, gives no water upon decomposition, which leads us therefore 

 to say that hydrofluoric acid contains no oxygen, and that it is analo- 

 gous to hydrochloric acid. Now we know by experimental demonstra- 

 tion that hydrochloric acid is composed of chlorine and hydrogen. It 

 is therefore logical to think that hydrofluoric acid is formed by the 

 combination of hydrogen with fluorine. 



This important experiment, made by skillful hands, did not, however, 

 compel a general belief in the existence of hydracids. 



The views of Lavosier concerning the part played by oxygen in the 

 formation of acids, ideas which had been opposed at first, were then 

 so generally admitted that many persons refused to accept the exist- 

 ence of hydrogenated acids at all. It was only after the memorable 

 researches of Guy Lussac upon cyanogen and hydrocyanic acid that it 

 was proved beyond discussion that energetic acids could exist which 

 contained no trace of oxygen. 



Furthermore, when we compare the acid compounds formed by chlo- 

 rine, for example, or sulphur with hydrogen we have two types of 

 combination which are entirely diflerent. 



Let us take one volume of chlorine and one volume of hydrogen. By 

 the action of light or of a spark from an induction coil they unite to 

 form two volumes of hydrochloric-acid gas, a compound having all the 

 properties of a very energetic acid. 



If we combine two volumes of hydrogen with one volume of sulphur 

 vapor we shall obtain two volumes of sulphuretted hydrogen gas, 

 which has, it is true, an acid reaction, but incomparably weaker than 

 that of hydrochloric acid. 



It is very evident that by virtue of its powerful reactions, by the 

 disengagement of heat which it produces upon contact with water or 



