Ferri Sulphas. Lond. Sulphate of Iron

"Take of iron filings, eight ounces; sulphuric acid, fourteen ounces; water, four pints. Mix the sulphuric acid with the water, and add the iron; then apply heat, and when the effervescence is over, filter the solution, and set it aside, that crystals may form. Evaporate the liquor decanted that it may again yield crystals. Dry them all."

Sulphas Ferri, Edin. Sulphate of Iron.

"Take of iron, sulphuric acid, of each, by weight, eight ounces; water, four pints. Mix the sulphuric acid with the water in a glass vessel, and add the iron to them; when the effervescence is over filter the solution through paper, and after due evaporation set it apart, that crystals may form. Having poured off the liquor, dry these upon bibulous paper."

1 Trans, of the Pharm. p. 98. 1829.

2 Old names of this salt: - misy, sory, calchantum (Pliny), sal martis, sal chalybis vitriolum ferri, vitriolum martis.

Ferri Sulphas, Dub. Sulphate of Iron.

"Take of iron wire, four parts; sulphuric acid, seven parts, water, sixty parts. Digest the mixture, that the metal may be dissolved, after which filter the solution through paper; finally, after due evaporation, set it apart, that crystals may form by slow cooling."

Syn. Sulfate de Fer (F.), Schwefelsaures Eisen (G.), Zwalvelzuures yzer (Dutch), Gron Vitriol (Banish), Solfato di Ferro (I.), Vitriola verde (S.), Ca-parosa verde (Port.), Unua Baydie (Tarn.), Casis (Hind.), Heera Cashsih (Duk.), Taroosee (Malay), Zungafmadenee (Arab.), Tootya Subz (Pers.).

In these processes part of the water is decomposed: the iron is oxidized by combining with its oxygen, while its hydrogen is dissipated in the gaseous form; and the oxide thus produced unites with the acid, and forms sulphate of iron, or rather sulphate of oxide of iron; which is dissolved in the undecomposed portion of the water. Concentrated sulphuric acid, nevertheless, scarcely exerts any action on iron at a low temperature, and water alone is very slowly decomposed by it, so that the rapid decomposition of the diluted acid by the iron must be ascribed to the sum of the affinities of the base of the acid for oxygen, and of the iron for oxygen being superior to that of the oxygen to the hydrogen of the water, which is therefore decomposed. The solution is of a pale-green colour, and, when evaporated directly, yields crystals of protosulphate of ironl: but if it be exposed for some time to the atmosphere, it attracts oxygen, becomes turbid, a sulphate of the peroxide is precipitated, and the salt obtained is a persulphate.

Qualities. - Sulphate of iron is inodorous, has a strong styptic taste : it crystallises in transparent, rhomboidal prisms, of a fine pale green colour, which redden the vegetable blues, are soluble in two parts of water at 60°, and three fourths of their weight of boiling water, and are insoluble in alcohol. It is precipitated nearly white from aqueous solutions by the alkalies, and also by ferrocyanate of potassa, but, on exposure to the air, the former becomes red, owing to the formation of the sesquioxide; the latter becomes blue, as a prussian blue. When exposed to the air, the crystals become opaque, and are covered with a yellow powder, owing to the attraction of the oxygen of the atmosphere by the salt, during its efflorescence. Exposed to heat, sulphate of iron undergoes the watery fusion, and loses six sevenths of its water; the crystals lose their form, and fall to powder; and in an increased heat the acid, partly in the state of what is termed Glacial Oil of Vitriol, is driven off, and the base remains in the state of a red oxide, the colcothar of vitriol of commerce.

According to Dr. Thomson1, 100 parts of the green sulphate consist of 26.7 of sulphuric acid, 28.3 oxide of iron, in the state of protoxide, and 45.0 of water.2 Mr. Phillips makes the proportions to be of acid 28.8, protoxide of iron 25.9, and water 45.3, or 1 equivalent of acid = 40.1 + 1 of protoxide =36+7 equivalents of water = 63; making the equivalent of the salt 139.1 (Fe S+ 7 H). The following substances decompose sulphate of iron: the earths, the alkalies and their carbonates, ammonia, lime-water, biborate of soda, phosphate of soda, hydrochlorate of baryta, nitrate of silver, acetate of lead, every salt the base of which forms an insoluble compound with sulphuric acid, and soaps: thence these are incompatible in formulae with this salt. It is also decomposed by all infusions of vegetable astringents. It should be preserved in alcohol.

1 This salt, which is known in commerce by the name of green vitriol, is prepared on a great scale from the native sulphurets of iron, by exposing them to the air and moistening them, till a crust of sulphate of iron is formed on their surface which is afterwards obtained in crystals by solution add evaporation. The Harz yields annually 985 cwt..

Medical properties and uses. - Sulphate of iron is tonic, emmenagogue, and anthelmintic.3 It is a useful remedy when exhibited with due caution, in all cases in which preparations of iron are indicated; but in improper doses it occasions pain of the bowels, nausea, and vomiting, and often proves hurtful by being too long taken. It has been given with advantage in diabetes, in the latter stage of phthisis, and in amenorrhoea depending on a weakened action of the blood-vessels. The dose is from gr. j. to v. combined with ammoniacum, rhubarb, myrrh, or bitter extracts, and extracts of conium and of aconite. It has lately been used, dissolved in water, as a lotion to cancerous and phagedenic ulcers.4

Officinal preparations. - Ferri Sesquioxydum, L. Tinctura Ferri Muriatis, D. Ferri Subcarbonas, E. Mistura Ferri Composita, L. Pilulae Ferri Composite, L.