556

ELEMENTS OF MATERIA MEDICA.

Composition.— The following table exhibits the composition of thissalt, according to Soubeiran {op. tit.) and Phillips (Transl. of Pharma -copceia).

Phillips. Soubeiran.

t ~-1 ^

Tartrate of Sesquioxide of Iron 1 . . 106 . . 48*18 . . Sesquitartrate of Sesquioxide 45

Tartrate of Potash.1 . . 114 . . 51*82 . . Tartrate of Potash.55

Ferro-tartrate of Potash . . . 1 . . 220 . . 100*00 . . ,, . 100

Soubeiran says it contains 13 per cent, of sesquioxide of iron; whereas,according to Mr. Phillips, the quantity is 18T8 per cent.

The ferro-tartrate of potash is to be regarded as a double salt, in whichtartrate of iron is the acid or electro-negative ingredient, and tartrate ofpotash the basic or electro-positive constituent. On this view, we com-prehend why ferrocyanide of potassium and the alkalies refuse to act onit in the way they do on the ordinary ferruginous salts, until an acid beadded. Geiger ( Handb. d. Pharm.) regards it as a combination oftartrate of iron and ferrate of potash.

Purity. — In commerce we frequently meet with an imperfectlyprepared compound, in which none or only part of the sesquioxide ofiron is in chemical combination with bitartrate of potash. In this stateit is only partially soluble in water, and the solution strikes a blue colourwith the ferrocyanide of potassium, and throws down a reddish-brownprecipitate with solution of potash.

Physiological Effects. —In its effects on the system it agrees, forthe most part, with other ferruginous compounds. Its taste, however, iscomparatively slight, its astringency is much less than the sulphate orsesquichloride, and consequently its constipating effects are not soobvious, and its stimulant influence over the vascular system is said tobe somewhat milder. These peculiarities in its operation are supposedto depend on the tartaric acid and potash with which it is in com-bination.

Uses. —It is not frequently employed, yet it is a very eligible prepara-tion of iron, and may be employed wherever the ferruginous tonics areindicated.

Administration.— The dose of it is from ten grains to half a drachm,in the form of solution or bolus, combined with some aromatic.

Ammo'nue Fer'ro-tar'tras. — Fer'ro-tar'trate of Ammo'nia .

This salt, commonly termed tartrate of iron and ammonia, orammonio-tartrate of iron, is occasionally employed in medicine. It wasfirst noticed by Mr. Aikin ( Lond. Med. Gaz. viii. 438).

It may be prepared by adding caustic ammonia to a solution of tartrateof iron (prepared by digesting together, for two or three days, one partof tartaric acid, dissolved in hot water, with two or three parts of ironfilings). The green solution thus obtained is to be evaporated to dryness;by a gentle heat (Aikin, op. tit.)

It is in the form of shining brittle fragments of a deep red colour, notvery unlike pieces of very deep-coloured shell-lac. It is very soluble injwater. Its taste is strongly saccharine.

Its general effects are analogous to those of the other ferruginouscompounds, except that it has very little of any astringency. Its advan-