35 S On the Identity of Silex and Oxygen, 



science the least advanced and the most difficult, especially 

 when our object of research is the exact estimation of the 

 principles which they contain : — it is thus, for example, that, 

 in dissolving steel in dilute sulphuric acid, the hydrogen 

 which is evolved, dissolves and carries off a part of the 

 carbon, the quantity of which varies according to a multi- 

 tude of circumstances." 



From this and other authorities, and from a prejudice, 

 which, I acknowledge, 1 have long been disposed to che- 

 rish, it may be inferred, that whatever emits smell cannot 

 be considered as a simple body, and hence, the purity of 

 hydrogen as an clement must be doubted ; that species, 

 however, which we obtain from the decomposition of water 

 by the metals, is certainly very objectionable, if there be 

 any truth in this observation ; for the gas is never free from 

 a ver^ perceptible odour, whether it has been procured by 

 means of zinc or iron. 



It is certainly not always prudent to generalize too freely 

 upon these subjects, yet it is difficult on some occasions to 

 avoid it entirely. The hydrogen gas, alluded to by M. Vau- 

 quelin, in these analyses, was undoubtedly impure, as 

 it contained a certain portion of carbon from the metal, 

 though not the whole ; for, finding this mode of operating 

 inconclusive, he at last had recourse to the sulphurous acid, 

 with which he apparently succeeded in separating the whole. 



Fluoric acid, from its peculiar effects upon the siliceous 

 compounds, deserves a particular notice in the present in- 

 quiry, especially as its whole history remains still clouded 

 with inconsistency and ambiguity] for, either the tables of 

 affinity respecting its habitudes are erroneous, or the acid 

 itself must be considered as a monstrous anomaly in the 

 doctrine of chemical attractions. These tables begin with 

 lime, and go on progressively with some of the earths and 

 alkalies to silex, the very last in the enumeration, with 

 which, by the way, it has never yet been united so as to 

 produce a true salt. From Bergman's experiment, we learn, 

 that he dissolved silex in fluoric acid, and that after the so- 

 lution had remained undisturbed for two years, a number 

 of crystals had formed at the bottom of the liquor in the 



• • vessel. 



