FERR

1;

it can do no good where the pain is produced from the pressure ofosseous spieulse, &c.

Eiders into Ferrum Ammoniatum. L. Tartar. Ferri. D. Tinct.Ferri Muriatis. L. D.Ferri Sulphas. L. E. D. P. Sulphate of Iron. Green copperas,Green vitriol, Sal martis, Ferrum vilriolalum. O. Take 5 vu j eachby weight of iron and sulphuric acid, Oiv of water; mix the sul-phuric acid with the water in a glass vessel, and add the iron ; whenbubbles cease to escape, filter the liquor through paper, and evaporatethat crystals may form, pour off the liquor and dry the crystals onblotting-paper.

Decomposition. The water being partly decomposed, its hydrogenescapes while its oxygen unites witli the iron, forming a suboxide,which combines with the sulphuric acid, and is dissolved in thewater that remains, forming a protosulphate or subsulphate of ironin solution, which afterwards crystallizes in rhombs of a green colour,soluble in water, but insoluble in alcohol. These crystals when ex-posed to a strong heat part with their sulphuric acid, and peroxideof iron remains, known by the name of Cai.cot.haB. See OxioumFerri Rubru.ii. P.

Incompatible with the alkalies, the earths, and their carbonates;—withthe borate of soda, the acetates of ammonia and lead, the muriatesof baryta and ammonia, the nitrates of potass and silver, the tartratesof potass and soda; and with soap. It is also decomposed byastringent vegetable substances, and a tannogallate of iron is formed,but it retains in that case most of its properties.

Medicinally the sulphate of iron is tonic and astringent, and in a largedose emetic. It is given in deses of gr.j to gr. v with bitters, &c, indebility and relaxation, and also as a vermifuge. M. Marc says it isfebrifuge.

It is used extensively to adulterate beer, to which it gives a fine frothyheading. When not in great quantity, however, it must be ratherwholesome than otherwise. It is also used extensively in dyeing,making of ink, &c.

Enters into Pil. Ferri cum Myrr. L. Sulph. Ferri Exsicc. E.Ferro-cyanates are salts formed with ferro-cyanic acid and alkalineor metallic bases. These salts were formerly called Triple Prussiatcs.Ferro-cyanatk of Baryta is prepared by digesting purified Prussianblue with a solution of pure baryta. It is soluble in water and isused in preparing ferro-cyanic acid. A similar salt is formed withmagnesia and with strontia.Ferro-cyanate of Peroxide of Ikon. See Prussian Blue.Ferro-cyanate of Potass, formerly Triple Prussiale of I'olass, is pro-

„1