HTDRATED PEROXIDE OF IRON. 
35 
tion, (if the iron is good,) but the length of time it takes is an 
objection to its adoption, at least in a case of urgency. There 
are few pharmaceutists but have in their possession a sulphate 
of iron pure enough for making this preparation. By em- 
ploying the sulphate ready made, the time of making is reduced 
one-third. 
Take of 
Crystallized Sulphate of Iron, in coarse powder, gxx. 
Sulphuric Acid, giij. 
Nitric Acid, (sp. gr. 1.4) giiiss. 
Water, Oiss. 
Add the sulphate of iron to the water, previously boiling in 
a suitable vessel, and when it is dissolved add the sulphuric 
acid. To the boiling solution the nitric acid is to be added 
in small quantities at a time, continuing the ebullition after 
each addition until the whole of the acid has been added and 
the solution has attained a deep reddish-brown color. The 
dark liquid thus obtained is a concentrated solution of the ter- 
sesquisulphate of iron, and forms a ready means of obtaining 
the hydrated per oxide. 
Another method which has been proposed is to take any 
quantity of nitric acid, specific gravity 1.3, and add powdered 
sulphate of iron in small quantities at a time until effervescence 
ceases, then applying heat to drive off the absorbed deutoxide 
of nitrogen. The only objection to this process is that the result- 
ing solution is a mixture of two equivaleuts of tersulphate, and 
one of ternitrate of the peroxide of iron, and when an alkali 
is employed to precipitate the oxide, an alkaline nitrate 
remains in solution which, if not wholly removed, would be 
more likely to irritate the stomach than the sulphate of the 
same base. 
However prepared, the strength of the solution should be 
known. Every hundred grains of the crystallized sulphate 
of iron employed, yields nearly thirty-eight grains of the 
hydrated peroxide; and by knowing the quantity of sulphate 
employed and of solution obtained, the percentage of oxide in 
