518

Metallic Preparations. — Iron.

part in.

is at a minimum of oxidizement; but while drying, it attractsoxygen rapidly from the atmosphere, and is converted into thered oxide, or a peroxide, containing, according to Proust, 48per cent, of oxygen. I have found that the precipitate com-bines with the largest proportion of carbonic acid, when thesolutions are mixed at a temperature of 150° of Fahrenheit;and filtration is necessary for separating it, the decantation ofthe clear fluid being very difficult, owing to the lightness of theprecipitate. The great solubility of the sulphate of soda ren-ders much subsequent washing unnecessary; and the precipitate,after being washed, should be dried in the paper on which it isfiltered, by a heat not exceeding 200°.

Qualities. — Precipitated subcarbonate of iron is inodorous,has a slightly styptic taste ; and when properly prepared is of achocolate-brown colour. It is insoluble in water, but acidsdissolve it with effervescence, disengaging the carbonic acid inthe gaseous form. It is decomposed by heat, and convertedinto the black oxide of the metal. In my experiments, tengrains of the dried subcarbonate, prepared with effloresced sub-carbonate of soda, lost 2*3 grains, when dissolved in muriaticacid; and the same quantity, prepared with the crystallized al-kali, and dried with great care, lost 1*4 ; so that prepared in theformer method, it contained 23 per cent, of carbonic acid, andin the latter 14 per cent.

Medical poverties and uses. —This preparation differs Jittlefrom the former preparation in its effects, except that it sitseasier on the stomach. The dose is from grs. iv. to grs. xxx.;given three times a day, combined with myrrh, or aromatics.Officinal preparations. Ferritin ammoniatum. L. Tartarum Ferri.D. Tinctv.ra Ferri Muriatis. L.

FERRI SULPHAS. Lond. Sulphate of Iron. 1"Take of iron, sulphuric acid, each eight ounces-, water,four pints. Mix the sulphuric acid with the water in a glassvessel, and to these add the iron ; then, when the effervescenceis over, filter the solution through paper, and evaporate itover the fire, so that crystals may form as it cools. Pour offthe water, and dry the crystals upon bibulous paper."Sulphas Ferri. Edin. Sulphate of Iron." Take of purified filings of iron, six ounces ,- sulphuricacid, eight ounces; water, two founds and a half. Mix, andwhen the effervescence is over, digest the mixture for sometime upon hot sand; then filter the solution through paper,and after^due evaporation set it apart, that crystals may form."

1 Old names of this salt : — mmj,sury, caichanium { (Pliny) sal marlis, sal chaly-his vitriolum ferri, vitnoltim mortis. Syn. Sulfate He Fer (F.) Schwefelsaures Eisen[G.) Solfato di Ferro (/.) Una Baydie {Tarn.) Casis (Hind.)