148 Remarks on Priestley’s Analysis 
mer:* consequently less water is decomposed, and 
therefore less oxygen combines with the iron, And 
it is well known, that the attraction of the sulphuric 
acid to the oxyd of iron is so much weakened, by 
an addition of oxygen to the latter, that it is preci- 
pitated from its solution: as is the case, when the 
sulphate of iron is dissolved in water and exposed to 
the atmosphere. The rust of iron also, which is of 
a higher degree of oxydation than the black oxyd of 
iron, cannot be dissolved in sulphuric acid but with 
much difficulty. 
It is next said, that finery cinder contains no 
oxygen, “because, when it is dissolved in the ma- 
rine acid, it does not dephlogisticate it as minium 
and other substances containing oxygen do.”——But 
Dr. Priestley allows, p. 12, and 47, that the red 
oxyd of iron, or rust of iron, contains oxygen; and 
yet it does no¢ oxygenate the muriatic acid. The 
truth is, that every substance containing oxygen has 
not that effect; which can only be produced when 
the mutiatic acid has a greater attraction to oxygen 
than the substance which contains it; or when.a 
substance, e.g. a metallic oxyd, is combined with 
more oxygen than it can contain, when dissolved in 
* Two ounces of iron, when dissolved in acids, will 
yield about 800 ounce-measures of air; but by passing 
steam over it, when red-hot, they yield 1054 ounce-mea- 
sures. See Priestley’s Experiments, vol. 1, p. 294. 
