Iron filings, with an equal quantity of nitre, thrown into a crucible red hot, are changed to the yellow oxide of iron, called Zwelfer's saffron of Mars : sublimed with muriat of ammonia, it becomes the flores martiales, viz. a muriat of ammonia coloured by iron. This metal is oxided by agitation in water, and by being digested with either fixed or volatile alkalis.

Iron combined with acids becomes an astringent substance; and upon its astringent, its tonic powers and medicinal virtues seem to depend; for by increasing the tone of the vessels, it increases their vigour and activity. Melampus cured a man of impotency by the rust of iron; which is the first record of its use as a medicine. Boerhaave thinks iron nearer allied to the human fluids than any other metal, and to be almost wholly soluble in them.

We have already remarked that medical utility and solubility in the fluids were too commonly considered as synonymous, and have pointed out the fallacy of the opinion. Iron is undoubtedly an astringent, and perhaps a tonic; since we have reason to think all metallic bodies, except lead, to be tonics. It possesses, however, apparently a quality found in no other metal, viz. a stimulus, by which many of its effects may be explained. One reason has been assigned for supposing it more friendly to the constitution than other metals, viz. the consideration that it is naturally an ingredient in the animal fluids,and that the red globules, whose proportion and vividness are apparently connected with the strength, seem to owe their colour to iron.

The medical uses of iron are almost confined to chronical disorders; in which its efficacy is considerable. In weak, lax, pale, and leucophlegmatic habits it strengthens the stomach, and chylopoietic organs in particular; and by its continued use the whole system is invigorated, the pulse raised, and every mark of health restored.

By the same corroborating power it promotes deficient, and restrains redundant, discharges, where the suppression and excessive flux equally arise from debility; but it increases fluxes, and confirms obstructions when they proceed from tension, rigidity, or spasmodic strictures of the vessels.

An aperient and astringent virtue has been attributed to different preparations of iron; but each is aperient or astringent, according to the state of the constitution of the patient who takes them, without any such property in themselves. Chalybeate waters are said to have similar effects on the constitution as iron. See Aquae. minerales.

In the chlorosis, iron, with aromatics, bitters, and aloetic purges, is often very useful. In this, as in most other cases, the crude iron filings, when minutely pulverized, excel any preparation; and are peculiarly proper,as they combine with the acids of the stomach.

The aloctics to be joined with iron in this disorder are the pillulae ex aloe cum myrrha, or vinum aloes: these may be taken not as purgatives, but as eccoprotics, to evacuate the intestinal contents only.

Iron scarcely in any instance occasions dyspnoea. Its ore has, according to Dioscorides, been injected in clysters to restrain diarrhoeas; and the water in which hot iron has been quenched is said to be useful when employed as a bath in gout or palsy. In malignant and obstinate ulcers it has been often used with success; and since the article on Cancers was printed, we have found the rust of iron strongly recommended both as a medicine and application in this disease. In roughness and chronic diseases of the skin, it has been recommended; and in the broad brown moles which rise slightly above the cuticle we have known the sul-phat of iron highly useful.

It was very commonly employed by the ancients in excessive discharges from the bowels, as in diarrhoea, cholera, lientery, dysentery; and is by many authors recommended as a vermifuge, either operating mechanically as filings of tin, or by its tonic power. In various diseases of debility, besides those already mentioned, it has been employed, viz. in intermittents, in hectics, in dropsies, tympanites, vertigo and pain of the head from relaxation, exhausted powers from venereal indulgences, in gleets; and by some respectable practitioners even in internal obstructions, particularly those of the spleen and mesentric glands.

Suppressed or an immoderate discharge of the menses are relieved by this salutary metal (see Menses); and it is sometimes employed to check haemorrhoidal discharges. In hypochondriac and hysteric complaints it is highly useful: and many of the true spasms, particularly in epilepsy, it is said to have relieved. We need not repeat what has been said of the tonic power of all the metals; nor what we have remarked respecting the effects of metallic tonics in this last disease. In the rickets it has been recommended; and though in fevers, or where the heat of the body is too great, iron is generally prohibited, yet in some low fevers it hath been administered in conjunction with nitre, it is said, with good effect. In a weak state, when low fever attended, a mixture of sal martis and sal nitri, in equal parts, has been given in doses of ten or twenty grains; but the fever in this case was apparently symptomatic only.

In some instances, iron occasions sickness and perturbation; a mild opiate must then be added, or the medicine taken in bed, half an hour before the hour of rising or of going to rest.

When improperly taken, it sometimes occasions anxiety, head ach, pains in the stomach and bowels, or spasms.

Iron we have said is injurious where the viscera are obstructed, or where an inflammatory tension accompanies it. This medicine should also not be employed when the stomach and bowels are overloaded. It should not be taken a little before or after meals, and be carefully purified from any particles of copper by-means of a magnet.

It has been the opinion of some respectable practitioners, and among the rest of Sydenham, that nature affords this remedy in a more useful form than art can supply. We shall therefore first mention the principal ores of iron employed as remedies. The first of these has had the sounding title of minera martis solaris. It is the pyrites of authors, the sulphurated iron of Hauy, iv. 65, and an astringent of considerable efficacy, as it contains a portion of alumen.