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Mftalmc Preparations. — Iron.

PART III.

into a saline mass, which is to be reduced to powder, andpreserved in closely stopped phials."

Of these three processes, those of the Edinburgh and theDublin Colleges are to be preferred, as they afford a perfecttriple salt; whereas much of the iron employed in the Londonprocess remains unaltered, or is at least only in the form of asimple oxide. In the London process, the iron is first oxidi-zed by the partial decomposition of the water, aided by theaction of the air, and the oxide thus formed unites with thesuperabundant acid of the supertartrate of potash : hence thedried mass consists of tartrate of potash and iron, mixed withoxide of iron, and some metallic iron. The subsequent ad-dition of water, and re-exposure to the air, are intended torender the oxidizement complete, and convert the whole tothe state of the triple salt; but as this is not effected, it is pro-bable that the proportion of supertartrate of potash ordered,is insufficient for the large quantity of the metal directed tobe used. In the Edinburgh and Dublin processes, the su-perabundant acid of the supertartrate of potash dissolves a#much of the oxide of the carbonate of iron as it can take up;and a clear solution is obtained, which, by evaporation, yieldsa true tartrate of potash and iron. As it is almost impossibleto procure this salt in crystals, the solution may be evapor-ated to dryness.

Qualities. — Tartrate of potash and iron is inodorous, has aslightly styptic taste, and is of a brownish green colour. It isvery soluble in water, and deliquesces, in some degree, whenexposed to the air, so as to require to be kept in closely stop-ped phials. The cold solution of the alkalies and their sub-carbonates do not decompose this salt; but it is instantly de-composed when boiled with any of them except ammonia andits subcarbonate, which in neither state affect it. The hydro-sulphuret of potash and infusions of astringent vegetables de-compose it, and are therefore incompatible in formula? with it.

Medical properties and uses. — This salt possesses the samemedicinal powers as the other preparations of iron; but fromits mildness, slight taste, and ready solubility, it is a more con-venient form for the administration of this metal to children,and in many cases in which the other saline preparations of itprove nauseating, and sit uneasy on the stomach. It is ad-vantageously given in all the cases in which chalybeates proveuseful: and is also extolled as a remedy in dropsy, in which itis supposed to exert both a diuretic and a tonic power. Thedose is from grs. x. to 5fs, given either in a state of solution,or in the form of powder or bolus, combined with an aromatic,or bitter.