RELATION OF THE BRITISH PHARMACOPOEIA TO PHARMACOLOGY. 571 
temperature of 212°, hydrated peroxide of iron retains one equivalent of water,, 
and is a definite protohydrate, Fe 2 0 3 ,II0. The chemical formula given under 
Ferri Peroxidum is quite right, but the name should be Ferri Peroxidum Hij- 
dratum. As it now stands, the name expresses one thing and the formula an¬ 
other. 
In the case of Ferri Peroxidum Ifydratum , neither the name nor the for¬ 
mula are sufficiently explicit. The substance really is a moist hydrated per¬ 
oxide of iron, and its formula, so long as it accords with the condition of being 
“recently made,” is Fe 2 0 3 ,3II0. It is a to-hydrated peroxide, not sesqitihj- 
drated, as the Pharmacopoeia formula indicates. In fact, only when the terhy- 
drate has been long kept under water, and has become crystalline and almost 
valueless for the chief purpose for which it is inserted in the Pharmacopoeia, 
namely, as an antidote to arsenic,—it is only then that the preparation has the 
formula assigned to it in the Materia Medica. Its Latin name should be Ferri 
Peroxidum Ilydratum Humidum. 
Ferri Sulphas Granulata.— This preparation and process is from the 
Dublin Pharmacopoeia, except that the desiccation of the granules in an atmo¬ 
sphere rendered dry by the presence of sulphuric acid is now omitted. A strong 
and recently prepared hot solution of sulphate of iron is filtered into a jar con¬ 
taining spirit of wine, the spirit being rapidly stirred meanwhile. The result is 
the formation of minute or granular crystals which are said to oxidize less readily 
than the ordinary crystals deposited by the slow quiet cooling of their aqueous 
solution. It is assumed in the Pharmacopoeia that the spirit simply acts me¬ 
chanically, for the same chemical formula is given for this as for the ordinary 
sulphate, namely, FeO,SG 3 -f 7 IIO. This is probably an error, for although 
Berthemot (Jouru. de Pharm. vol. xxv. p. 206) once stated that the crystals 
under these circumstances retain their full amount of water of crystallization, 
Gmelin (Cav. Soc. Trans, vol. v. p. 240) asserts that alcohol causes the precipi¬ 
tation of a white “partly dehydrated” salt; and again, Bonsdorf (ibid.) 
shows that alcohol withdraws water from sulphate of iron and causes the crystals 
to turn white. Four specimens of granulated sulphate of iron prepared for me 
in the laboratory of this Institution by Mr. P. W. Squire, and analysed by an¬ 
other student, Mr. Herbert Smith, yielded an amount of water more nearly 
corresponding with a sulphate having six instead of seven equivalents of water 
of crystallization, but the amount seems to be variable. 
Selmi, Geiseler, Bonsdorf, Abich, Boudet, and Poma, have all tried to pre¬ 
serve sulphate of iron, but have failed more or less. Buspine (Pharm. Journ. 
vol. x. p. 308) dried the ordinary crystals at 86° Fahr. in a closet, -when they 
soon effloresced, then powdered and placed them in well-stoppered bottles. He 
stated that they might be kept for any length of time. It would seem that 
crystals of sulphate of iron contain water not in a state of combination, but sim¬ 
ply resting between the plates of the crystals, and that this water carries oxygen 
from the external air to the interior of the crystals; in this way the crystals 
or masses of crystals become oxidized. If this mechanically adherent water be 
got rid of, or, as in the Pharmacopoeia process, be prevented from accumulating, 
then the'crystals do not oxidize quite so readily. 
Ferrum Bedactum.— The test, or rather method of analysis given for this 
substance in the Materia Medica is that proposed by Draper (Chem. Hews, 
vol. i. p. 114). 
Ferrum Tartaratum.— The proportions of oxide of iron and acid tartrate of 
potash here ordered are somewhat different from those previously recommended ; 
they are those shown by Bastick (Pharm. Journ. vol. x. p. 444) as the best, 
giving the potassio-tartrate of iron, or tartarated iron as it is now termed, the con¬ 
stitution (KO,Fe 2 G 3 ,T) which Soubeiran and Capitaine had previously indicated 
it to possess. The percentage of oxide of iron also it is, in the Materia Medica, 
