540

ELEMENTS OF MATERIA MEDICA.

neuralgia, and in some cases it gives complete, in others partial, relief.But in many instances no benefit whatever is obtained from its use, andin one case in which I prescribed it, the patient fancied it increased hersufferings.

Mr. Carmichael, as I have before mentioned (p. 537), has recom-mended it as a remedy for cancerous diseases.

The use of the hydrated sesquioxide of iron, as an antidote for ar-senious acid, has been before noticed (p. 396).

Administration. —The usual dose of this preparation, as a tonic andemmenagogue, is from ten grains to half a drachm, combined with aro-matics, to enable it to sit more easily on the stomach. In tic douloureuxit is given in much larger doses, as from half a drachm to two, three, orfour drachms.

Emplastrum Oxidi Ferri Rurri, Ph . Ed.; Emplastrum Thuris,Ph . Dub. (Litharge plaster, fbij.; frankincense [concrete juice of PinusAbies] fbss.; red oxide of iron, Siij. M. Ph. Dub. In the EdinburghPharmacopoeia, resin, wax, and oil, are substituted for the frankincense,and the quantity of oxide is nearly three times as much).—This is the oldemplastrum, roborans or strengthening plaster, and is employed, spreadon a leather, as a mechanical support and slight stimulant, in mus-cular relaxation, lumbago, weakness of the joints, &c.

Fer'ri Ox'ydum Nigrum.—Black Oxide of Tron.

History. —It was first employed as a medicine by Lemery in 1735.It is the martial Ethiops (.rEthiops martialis) of some writers, and theoxydum ferroso-ferricum of Berzelius . It is sometimes termed the mag-netic oxide.

Natural History. —It occurs in the mineral kingdom under the nameof magnetic iron ore, the massive form of w'hich is called native load-stone. It is found in Cornwall , Devonshire, Sweden , &c.

Preparation. —In the Dublin Pharmacopoeia it is directed to be pro-cured by washing and drying the scales of the oxide of iron ( ferrioxydi squamat), and then separating them from impurities by means of amagnet. They are afterwards to be reduced to a very fine powder bylevigation and elutriation.

Other modes of preparing this compound are described in chemicalworks. The above is a cheap method, and yields a product sufficientlypure for the purposes of medicine. The process of the Paris Codex isregarded as a superior one. It consists in covering filings of iron withwater, and exposing the mixture to the air ; then, by elutriation, separat-ing the black powder.

. Properties. —It is a velvet-black pow'der, soluble in hydrochloricacid without effervescence, and magnetic.

Characteristics. —Its hydrochloric solution affords a green or green-ish-brown precipitate with a caustic alkali, and a greenish or blueprecipitate with ferrocyanide of potassium. Its other characteristics arethe same as those of the ferruginous compounds generally.

Composition. —It is a mixture or compound of protoxide and sesqui-oxide of iron. According to Mosander (Turner’s Elemetns of Chemistry),scales of iron have the following composition: —