"FLUORIC ACID. '&J 



results similar to those above stated. This, I suppose, is one 

 of the many errors that have secretly crept into repute, and 

 has been believed, because never subjected to the test of experi- 

 ment. 



The action of concentrated sulphuric acid on subsilicated Sulph. acid ex- 

 a .,..., , _ . . . . . pels silicated 



fluoric acid, is similar to that of muriatic acid gas, occasioning fl UO ricacidga» 



a disengagement of silicated fluoric acid gas. Facts which from subsili- 



ippear to prove, that water is absolutely essential to the exist- acir j # 



ence of this acid. 



Boracic acid decomposes it, in a very different way, not from Boracic acid 



any predominant affinity for the water, but in consequence of J! n,te . s Wlt j \ the 



a stronger attraction for the fluoric acid itself. Silicated fluoric and both acids 



acid of course is not produced : but liquid fluoboracic acid and ar , e precipitat- 

 . ... J ^ ed along with 



the silex is precipitated in a gelatinous state, as when ammonia thesilex. 

 is employed. 



These are the principal facts I have to notice respecting this Subsilicated 

 acid. Before I conclude, I shall briefly mention a few other act3 oll the 

 circumstances. Applied to the tongue, in its concentrated state, tongue, and 

 it produces a very painful sensation, like that which str °ng P"" 01 " 

 muriatic acid does, and it has a very similar effect on the 

 cuticle. It does not appear to erode glass, for I have kept it in 

 bottles of this substance more than a month without any action 

 being perceptible. Exposed to the air, it slowly and almost 

 completely evaporates, there being only a very trifling silicious 

 residue ; and when gently heated in an open vessel, it is rapidly 

 dissipated in white fumes. 



Sect. ii. On the Combinations of silicated fluoric acid Gas, and 

 the subsilicated Fluoric, and the fluoric Acids with Ammonia. 



M. Gay Lassac has shewn that silicated fluoric acid gas, Silicated fluo- 

 like carbonic acid gas, condenses twice its volume of the vola- condenses 

 tile alkali.* The experiment I have several times repeated, twice its vo- 

 and constantly with the same result, no difference appearing o^thfrd^nti 

 when the acid gas was added in great excess to the alkaline, weight of am- 

 or the alkafne to the acid. This being the case, and knowing monu « 

 the specific gravity of the two gases,f 100 parts by weight 

 of silicated fluat of ammonia seem to consist of 



* Vide Mem. d'Arcueil, Tom. II. 



f According to Sir H.Davy, 100 cubic inches of ammonia, barom. 

 30, therm. 60, weigh 18 grains. It is thil estimate which I have taken. 



24' $ 



