part in. Metallic Preparations. — Iron.

525

into a glass vessel, pour on the acid, and agitate it occasionally;then set it aside that the faeces may subside, and pour off theliquor: evaporate this slowly, to one "pint, and when it is cold,add the spirit."

TINCTURA MURIATIS FERRI CUM OXIDO RU-BRO. Dub. Tincture of Muriate of Iron, with the Red Oxide." Take of red oxide of iron, an ounce,- muriatic acid, fourfluid ounces ; rectified spirit of wine, a sufficient quantity. Di-gest the oxide with the acid for twenty-four hours; then boilthe solution for half an hour; evaporate the filtered solutionto the thickness of honey, and when it is cold, add rectifiedspirits of wine, with frequent agitation, until the specifiegravity of the tincture be, to that of distilled water, as 1050 to1000."

Of the formuhe given for the preparation of this tincture,those of the London and the Dublin pharmacopoeias are to bepreferred. The metal, as ordered in them, is in a higher stateof oxidizement, and forms at once, by its combination with theacid, an uniform compound soluble in alcohol; whereas, byfollowing the Edinburgh process, the solution is a mixtureof the above muriate, and of the less soluble or green mu-riate', the black oxide not being all completely oxidized; andit is not till after the exposure to air, and by attracting oxy-gen, that it is converted altogether into the more soluble mu-riate. Hence the Edinburgh preparation cannot be always ofan uniform and fixed strength, which, for an active medicine,is amattef of much importance. The introduction of the lastpreparation by the Dublin College is superfluous.

Qualities. — The alcoholic solution of muriate of iron is of abrownish yellow colour, has a peculiar odour and a very styp-tic taste. It contains the iron in a state of oxymuriate; andwhen it is distilled, this acid comes over, and leaves a blackoxide of iron in the retort. With tlte alkalies and their carbo-nates it gives a red precipitate; strikes a black colour with in-fusions of astringent vegetables; and forms with mucilage ofacacia gum, an orange-coloured jelly. Hence these substancescannot enter into compositions with this tincture.

Medical properties and uses. — This is an active and elegantpreparation of iron, well adapted for all the diseases in whichchalybeates prove serviceable. It is also recommended indysury depending on spasmodic stricture of the urethra, inwhich case it is given in doses of five or six drops, repeatedevery ten or fifteen minutes, until nausea be induced. It isalso used externally, as a styptic in cancerous and loose fun-

• When iron filings are dissolved in muriatic acid, and completely excluded from thsair, a muriate is formed insoluble in spirit of wine. Davy's Researches, p, ISO.