071 different Comhihations of Fluoric Acid, 3B1 



facts, it may be concluded, that indenendent of water, 

 which appears to be essential to its existence, 100 parts of 

 it consist of 28-34 ammonia 



71-66 acid 

 100 00 

 Subsilicatei fliiat of ammonia has a pungent saline taste. 

 It just perceptibly reddens litmus paper. Slowly evapo- 

 rated, it forms small transparent and brilliant crystals. The 

 larsiest I could obtain, appeared to be tetrahedral prisms. 

 The solid salt is -very soluble in water, but is not deliques- 

 cent. When heated it appears to sublime unaltered. It 

 is curious that the solution of this salt, when evaporated by 

 a heat near its boiling point, powerfully erodes the glass or 

 porcelain vessel, and a residuum of silex appears, on the 

 addition of water, to redissolve the salt. This erosion and 

 residue of silcx I have seen produced three times following, 

 with the same quantity of salt. I mention the fact, which, 

 I believe, was before observed by Scheele, without at- 

 tempting an explanation of it. It may perhaps be said, 

 that as the water evaporates, the affinity of the subsilicated 

 fluat for silex increases. 



Subsilicated fluat of ammonia is decomposed by the sul- 

 phuric acid, and by muriatic acid gas, and also by the fixed 

 alkalies and by ammonia. 



Sulphuric acid expels from it, siiicated fluoric gas and 

 hydrattd fluoric acid fumes. 



Muriatic acid gas acts slowly on it, and effects its de- 

 composition apparently through the medium of its water. 

 A little of the crystalline salt was introduced into muriatic 

 acid gas in ajar over mercury. In a short time some .siii- 

 cated gu3 was produced, as the siliceous deposition, on the 

 addition of water, indicated. Strong muriatic acid was 

 su'ostituled for the acid gas. Now no apparent change 

 took place;., for, on evaporating the acid, the residue, de- 

 composed by sulphuric acid, afforded only siiicated fluoric 

 acid gas. 



The alkalies form by the decomposition of this salt, the 

 same compounds that they do by their action on subsili- 

 cated fluoric acid. 



I'olash expels the ammonia, and produces the siiicated 

 fluat and (kiat of potash, as MM. Gay Lussac and Thenard 

 have described. 



The changes occasioned by soda appeared to me similar; 



but the geiulemen just mentioned, assert that this alkali 



precipitates the whole of the silex, and does not form a 



triolc salt with it and part of the acid. 



' Ammouia 



