Ferrum Vitriolatum. P.L. 1787. Sal Martis. P.L. 1745.
Sal, seu Vitriolatum Martis. P.L. 1720.
_Sulphate of Iron_, formerly _Green Vitriol_.
QUALITIES. _Form_, crystals, which are rhomboidal prisms, transparent,
and of a fine green colour; when exposed to the air they effloresce, and
at the same time become covered with a yellow powder, owing to the
attraction of oxygen; when exposed to heat, they undergo watery fusion,
and at a higher temperature, the acid is driven off and the peroxide of
iron alone remains, which in commerce is known by the name of
_Colcothar_. CHEMICAL COMPOSITION. According to Dr. Thomson, it consists
of 27·7 of sulphuric acid, 28·3 of protoxide of iron, and 45 of water; 8
parts, however, of this water, exist in combination with the oxide of
iron. The Medicinal Dynameter will shew the proportion of protoxide in
any given weight of this salt. SOLUBILITY. It is soluble in two parts of
water at 60°, and three-fourths at 212°. The solution reddens vegetable
blues. It is insoluble in alcohol; when however the iron is farther
oxidized, it becomes soluble in that menstruum.[507] INCOMPATIBLE
SUBSTANCES. Every salt whose base forms an insoluble compound with
sulphuric acid; _the earths, the alkalies and their carbonates_; _borate
of soda_; _nitrate of potass_; _muriate of ammonia_; _tartrate of potass
and soda_; _acetate of ammonia_; _nitrate of silver_; _sub-acetate and
acetate of lead_; _and Soaps_. Whether the medicinal virtues of a salt
of iron are injured by combination with astringent vegetable matter,
seems to admit of doubt. Such substances have been usually ranked
amongst the _incompatibles_, but I am disposed to think without
sufficient grounds, for I have frequently witnessed the salutary effects
of iron when exhibited in this questionable state of combination—may not
the absorbents be more disposed to take up iron, when combined with
vegetable matter, than when it is presented in a more purely mineral
form?[508] MEDICINAL USES. Tonic, astringent, emmenagogue, and
anthelmintic; in large doses, it occasions griping in the bowels. DOSE,
gr. j to v, combined with rhubarb, or some bitter extract. (_form: 72,
87._) If given in solution, the water should be previously boiled, or
the oxygen contained in the atmospherical air, which is diffused through
it, will partially convert the salt into an _oxy_-sulphat, and render it
insoluble. As an external astringent it is useful in the aphthæ of
children.[509] OFFICINAL PREP. _Mist: Ferri comp:_ L. (=K=) _Pil: Ferri
comp:_ L. (=J=).