Preparation and Composition. This salt is made by mixing officinal solution of citrate of iron and water of ammonia, evaporating at a heat of 150° or less to a syrupy consistence, and then drying on glass plates. The chemical composition of the resulting compound is not exactly determined; but it probably consists of one equivalent of citric acid, one of sesquioxide of iron, and one of ammonia. Mr. Redwood found the salt of commerce to contain variable proportions of the sesquioxide, from 31 to 34.5 per cent. (Pereira, Mat. Med., 3d ed., p. 793.) When the officinal salt is incinerated in the air, it yields 26.5 per cent, of the sesquioxide.

Properties

This salt is in very thin, shining scales, of a bright, almost ruby-red colour, and of a sweetish or acidulous, slightly chalybeate, very feebly styptic, and not disagreeable taste. It is readily soluble in water, but almost insoluble in alcohol. Ferridcyanide of potassium does not change it blue; though with the ferrocyanide it yields a copious blue precipitate, and caustic potassa and lime-water decompose it, throwing down the sesquioxide with escape of ammonia. It is not decomposed by the carbonates of the alkalies. I am told that ammonia escapes when it is heated.

Medical Uses

All that has been said of the medico] applications of tartrate of iron and potassa, and tartrate of iron and ammonia, is equally applicable to this salt, which is closely analogous to them in composition and properties. It is an excellent chalybeate, and may be given whenever it is desired to bring the system under the influence of iron, and a soluble preparation is wanted. It is less calculated than some other soluble salts of iron, to meet the indications for the tonic and astringent effects of the chalybeates on the alimentary mucous membrane. The dose is from five to thirty grains, the former being sufficiently large for a commencing dose in ordinary cases.

Several other salts of iron have been recommended at different times, and received more or less attention, of which very brief notices must suffice; as none of them have come into general use, and probably none are capable of producing effects which cannot, to say the least, be quite as conveniently and advantageously obtained from those already described.