‘of Atmospherical Air, €c. 147 
fallen into this error, since he informs us, in the 
_gd vol. of his Experiments, p. 505, that putting 
60 grains of finery cinder, finely pulverized, into 
each of the three acids, and leaving them two or 
‘three days to digest, he found, that of that which 
had been in the vitriolic acid, and also of that which 
had been in the marine acid, there remained 15 
grains undissolved: 45 grains out of 60, there- 
fore, were dissolved. ‘That 15 grains remained 
undissolved was, perhaps, owing to a deficiency of 
acid, or want of time; or, what is more probable, to 
carbonaceous or vitreous matter and other impurities, 
which the common finery cinder for sale contains. 
And of this he seems to have made use; for, of 
a homogeneous mass, either the whole or none can 
be dissolved by anacid.* This is confirmed by the 
circumstance, that the same residuum was found 
in the muriatic acid, which Dr. Priestley admits to 
be capable of dissolving that oxyd. 
That the solution of this finery cinder, in the di- 
luted sulphuric acid, is not so rapid as the solution 
of iron in the same acid, cannot be surprising, if it 
be considered, that iron is more oxydated by the 
decomposition of water, in a red heat, than by a so- 
lution of it in diluted sulphuric acid ; since much 
less hydrogenous gas is produced from the same, 
quantity of iron by the last method, than by the for- 
* Bergman. 
