• Dr Davy's Eafperiments oii Siltcated Fluwic Add Gas. 245 



^^-and, silicated fluorine acid, of two proportions of fluorine and 

 one of silicium, according to my brother'^s early views,* this sili- 

 cated fluate of lime will contain the same proportion of fluorine 

 as fluor-spar. <^^-oi; c:^ ,..:.< /; -v 



Similar trials were next made of silicated fluoric acid gas on 

 magnesia, al amine, and barytes. With magnesia it united 

 readily, both when cold and heated, but without ignition. The 

 compound, judging from the slight examination which I made 

 of it, is analogous to that of lime ; without taste, insoluble in 

 water, infusible before the blowpipe, decomposed by the action 

 of the sulphuric and muriatic acids — the acid gas being ex- 

 pelled by the former, and by the latter the compound resolved 

 into a diliquescent subsilicate and free silica. With alumine 

 and barytes, it also united, but to a less extent ; and it was again 

 expelled by sulphuric acid. 



On the action of the oxides of the common metals on silicated 

 fluoric acid gas, I have yet made but few experiments. In the 

 instance of peroxide of iron, of black oxide of manganese, — 

 the fusible oxide of antimony, the red oxide of mercury, on the 

 contact of the gas, a portion of it was absorbed ; and probably 

 combinations were formed superficially like the preceding. They 

 may be deserving of particular inquiry. The peroxide of iron 

 absorbed most gas, and gave it off" most readily when acted on 

 by concentrated sulphuric acid. 



M. Berzelius, in an elaborate and able paper on the fluoric 

 compounds,"!* expresses it as his opinion, that silicated fluoric 

 acid gas is merely a fluate of silica, and states, that it is capa- 

 ble of entering into combination only with neutral fluates, with- 

 out suff*ering decomposition, — and that, when one portion of its 

 silica has been separated, it can be replaced only by an alkali, 

 an oxide, or by water. 



The conclusion at which I have arrived from my own expe- 

 riments, is necessarily in opposition to that of this distinguished 

 chemist, and in accordance with the commonly received opinion, 

 namely, that the gas is an acid, and capable of entering into 

 direct union with certain oxides, as it was well known before to 



• PhiL Trans. 1814. 



t Annales de Chlmie et de Physique, torn. xxviL 



