146 Remarks on Priestley's Analysis 
buted, by the old chemists, to the phlogiston of the 
metals; but as the antiphlogistians maintain, that it 
is owing to a decomposition of water, they are de- 
sired by Dr. Priestley to shew, what is become of 
the other constituent part of water, the oxygen.— 
He had undoubtedly forgotten, that iron, as well as 
all other metals, are in the state of oxyds when 
combined with acids; and that they are precipitated 
from them in that state with a considerable addition 
of weight. In dissolving iron, therefore, in diluted 
sulphuric acid, the oxygen of the water combines 
with the metal, and it is by this means that the 
hydrogen is set at liberty; which, combining with 
caloric, is exhibited as hydrogenous gas. And this 
process is analogous to the decomposition of water 
by red-hot iron; the product of which is the same 
gas and the black oxyd of iron, which is called 
finery cinder. But Dr. Priestley thinks that this is 
impossible ; because, says he, finery cinder is not 
soluble in vitriolic acid. This, however, is a mis- 
take. I decomposed water by red-hot iron wire. 
To avoid all mistakes, I made use of the scales only 
which fell from this wire by bending it, so that I 
Was sure that no iron, in its metallic state, was pre- 
sent. These scales I put into a phial with some 
diluted sulphuric acid, and kept it in a heat which 
sometimes made it boil. After several hours, the 
whole was dissolved without effervescence. It is 
rather extraordinary that the Doctor should have 
