298 Mr. Cooper on the Persulphates of Iron. [Aprit, 
remaining oxygen, and form a ternary compound. And where 
hydrogen is not present, such a combination may be at once 
established. 
It is not easy to determine which of these opinions is just. 
The reason above stated renders the latter, perhaps, more 
probable ; and the view which leads to the conclusion, that in 
the constitution of the acids and alkalies the three elements, 
when present, are in simultaneous combination, leads also to a 
similar conclusion with regard to the constitution of the neutral 
salts. Ifthis be adopted, neutralization is not the saturation of 
acid with alkali, and the subversion of the properties of the one 
by the opposed action of those of the other, but is the change of 
composition of both, and the quiescence of the elements in that 
proportion in which their affinities are in a state of equilibrium 
without any excess. The compounds, therefore, have little 
activity ; and energy of action is restored only by the reproduc- 
tion of substances, which, by their mutual attractions, tend to 
the same state of quiescence. 
All these results display more fully the extensive relations of 
the two elements, oxygen and hydrogen. They do not. act 
merely in opposition, as had been imagined, but more frequently 
in union, producing similar effects. Hydrogen is of nearly 
equal importance with oxygen; and the principal’ details of 
chemistry consist in their modified action on inflammable and 
metallic bodies. 
ArTIcLe VI. 
On the Persulphates of Iron. By Mr. Cooper. 
(To Dr. Thomson.) 
DEAR SIR, 89, Strand, March 16, 1819. 
_ I FEEL very happy in being able to confirm your analysis of 
the persulphates of iron contained in Vol. X, No. LVI, of your 
Annals of Philosophy, and also to verify the conjecture you have 
thrown out of there being a persalt of iron containing an excess 
of sulphuric acid. This salt I have formed by boiling recently 
precipitated peroxide of iron (from nitric acid by ammonia) in a 
considerable excess of sulphuric acid ; the solution goes on but 
slowly ; but when obtained, if it be evaporated to the consistence 
of syrup, it will in a few days deposit crystals : these are the 
bipersulphate of iron. I find the crystallization to succeed better 
when a small excess of acid is present. The form of the crystal is 
that of an octohedron ; some of the solid angles are truncated, 
some of the edges are bevelled, and in others the edges are 
truncated, while others of them are the perfect octohedron. 
These crystals aye permanent, and are perfectly transparent and 
