Iron: a greyish, hard metal, between seven and eight times specifically heavier than water: distinguished from all other metallic bodies, in its metallic state, by its attracting, or being attracted by, the loadstone; but losing this attractive power on being reduced, by fire or menstrua, to a calx: not fusible without an intense white heat, and calcining, by a continuance of a weaker heat, first into blackish scales, and afterwards into a dark reddish powder: corrosible by moist air into a reddish yellow rust, and soluble. in all acids, from which it' precipitates all the common metallic bodies except zinc: forming with the marine acid a yellow, with the nitrous a dark red, and with the vitriolic a pale green solution; which is changed to an inky blackness by the addition of a little galls, and by most of the other vegetable astringents, and to a reddish or purple by a mixture of astringents with a minute proportion of any alkaline salt. All the solutions, by whatever acid effected, on the addition of a lixivium of alkaline salts that have been calcined and fully impregnated with animal coals(a), are changed to a deep blue, and on standing de-posite the iron in form of a powder of the same colour. By these characters, a most minute portion of iron may be discovered in liquors.

Ores of iron, and minerals more slightly impregnated with it than those which are stridtly

(a) Volatile alkaline spirits may be completely saturated with the matter which tinges dissolved iron blue, by digest-ing them with the pigment called Prussian blue; from which they acquire a yellowish or greenish tincture, leaving the iron in form of ochre or a rusty coloured cax. called ores, are common in most parts of the world: the red and yellow earths and stones generally owe their colour to an admixture of this metal. The iron, extracted from the ore by fusion in large furnaces in mixture with the fuel, is impure and brittle: being again laid on burning charcoal in a smaller furnace or forge, and melted down, a quantity of sulphu-reous scoria separates, the iron proves less fusi-ble, less brittle, and by two or three repetitions of the process, becomes tough enough to be forged into bars. The iron thus purified is employed as an article of the materia medica in two dates.

(a) Volatile alkaline spirits may be completely saturated with the matter which tinges dissolved iron blue, by digest-ing them with the pigment called Prussian blue; from which they acquire a yellowish or greenish tincture, leaving the iron in form of ochre or a rusty coloured cax.

Caeruleum berolinense; Prussian blue.

1. Ferrum Pharm. Lond. Ferrum Jive Mars Pharm. Edinb. Iron, or forged iron: iron in its softest state; capable of being easily filed; acquiring little or no additional hardness on being made red-hot and quenched in water; appearing, when broken, of a fibrous texture; exceeding difficult of fusion, and perhaps not fusible at all by common fire without the contact of the fuel or other additions.

2. Chalybs. Steel: iron in a hard state, so as to refill the file, or acquiring this hardnefs by heating and quenching it; when broken, of a fine granulated texture; much easier of fusion, somewhat more difficult of solution, and somewhat less subject to rust in the air, than soft iron. Iron, cemented in close vessels, with vegetable or animal coals, becomes steel; and steel, kept red-hot for some time in an open vessel, becomes soft iron again.

This metal, when dissolved, discovers a strong austere corrugating taste, and contracts and hardens all the vascular and soft fibrous parts of animals. To constringe and corroborate the animal solids appears to be its primary medical operation.

In weak, lax, pale habits, and in chronical disorders proceeding from languor and debility, cachectic hypochondriacal, and others, this metal has generally good effects: strengthening the stomach, and chylopoietic organs, and the system in general; quickening the circulation and raising the pulse; rendering the blood more florid, and as it were expanding and rarefying the juices; promoting, when they are desicient, and restraining, when immoderate, the secretions that are made from the blood, as perspiration, urine, and the uterine purgations; but for the most part binding the belly, though this evacuation also, in some circumstances, it promotes.

By the same corroborating power, whereby it promotes deficient and restrains redundant discharges where the suppression or flux arise from debility and relaxation; it, contrariwise, increases fluxes and confirms obstructions when they proceed from tension, rigidity, or spasmodic stric-tures of the vessels. Where either the circulation is quick, or the habit plethoric; by increas-ing the blood's velocity, and all the plethoric symptoms, it produces heaviness, dulness, vague heats and flushings, or kindles more dangerous fevers or inflammations, or bursts some of the over-distended small vessels.

In some constitutions, even where iron is proper and salutary, particularly in hysterical and hypochondriacal cases, and where the stomach is very weak, it is apt at first to occasion great sickness and perturbation: Sydenham observes, that these inconveniences may be, in some mea-sure, prevented by beginning with very small doses, and giving it for a while only at bed-time, in conjunction with a slight opiate (a). In other circumstances, it is commonly taken in the morning and afternoon, and moderate exer-cife used to promote its action. The dose in all cases should be small, and rather repeated than enlarged: a grain or half a grain of the metal, dissolved or in a soluble state, is generally a sufficient dose. Nidorous eructations, and the alvine feces being tinged of a black colour, are marks of its taking effect.

Iron is sometimes given in subftance, reduced into fine filings; which answer, in many cases, as well as its most elaborate preparations; but their action is less certain, as depending upon their meeting, in the first passages, with juices capable of dissolving them; they are likewise the most subject, when they do act, to produce troublesome eructations, probably from the property of this metal of yielding copious fetid vapours during its dissolution. The dose of the silings is from two or three grains to a scruple and more: it is probable that the whole quantity taken does not prove operative, even when the stomach abounds most with acidities; for on digcsting a scruple of the filings in a quarter of a pint or more of strong vinegar, a very consider-able proportion remains undissolved.