S46 Dr Davy's Experiments on Silicated Fliwric Add Gas, 



have done with ammonia. M. Berzelius expressly states, that 

 he failed in his attempts to combine it directly with lime. To 

 what circumstance this failure was owing, I shall not attempt 

 to point out. The negative result, no doubt, led him to adopt 

 the idea that the gas is not an acid. 



In farther support and illustration of its acid nature, I may 

 mention, that it instantly reddens litmus paper introduced into 

 it, carefully dried ; and that, though the silicated fluate of am- 

 monia is decomposed by muriatic acid gas, silicated fluoric acid 

 gas being disengaged, and muriate of ammonia formed, it is 

 not decomposed by carbonic acid gas ; but, on the contrary, 

 the carbonate of ammonia is decomposed at the temperature of 

 sublimation by silicated fluoric acid gas. 



From the similarity of properties of silicated fluoric and fluo- 

 boracic acid gas,'it seemed probable a priori^ that the latter dlso 

 might be capable of entering into union with lime, magnesia, &c. 

 directly ; and the single experiment I have made on the former 

 earth has confirmed the conjecture. As soon as the fluo-boracic 

 acid gas was introduced into a tube over mercury, containing 

 some quicklime, its absorption commenced, and was promoted 

 by the application of heat ; but, though pretty rapid, it was not 

 attended with ignition. The compound formed was very simi- 

 lar to the silicated fluate of lime, — but rather more easily fu- 

 sible. Acted on by concentrated sulphuric acid, it emitted the 

 peculiarly dense fumes characteristic of fluo-boracic acid vapour. 



As regards the question of the nature of the fluoric principle, 

 the facts adduced are but of little weight ; however, their bear- 

 ing seems to be most in favour of the hypothesis which is now 

 most generally received, — the one already alluded to, that the 

 fluoric principle is analogous to chlorine. 



Malta, April 2. 1834. 



