part hi. Metallic Preparations—Iron.

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necessarily vary from variations in the conduct of the pro-cess.

Qtialities. —It is inodorous, has a styptic taste, and a red-dish-brown colour; dissolves in acids with effervescence ; andis decomposed by heat.

Medical properties and uses. — The rust of iron is tonic andemmenagogue. Next to the black oxide it is the least active ofthe preparations of this metal. It has lately been recom-mended with much confidence, both as an internal remedy,and an external application in cancer. 1 In large doses it oftenoccasions uneasiness at the stomach; yet Cullen says, " Wehave always found the simple rust as effectual as any otherpreparation ; and the stomach bears it better than any "other."It is given in the form of pills, combined with aromatics andbitter extracts. The dose is from grs. iv. to 3j. given twice aday.

Officinal preparation. Tinctura Muriatis Ferri. D.

FERRI SUBCARBONAS. Lond. Subcarbonate of* Iron.

" Take of sulphate of iron, eight ounces ; subcarbonate ofsoda, six ounces ; boiling water, a gallon. Dissolve separatelythe sulphate of iron and the subcarbonate of soda in eight pintsof water; then mix together the solutions, and set the mixtureaside, that the powder may subside; then pour off the super-natant fluid, wash the sub-carbonate of iron in hot water, anddry it, wrapped up in bibulous paper, with a gentle heat." i

Carbonas Ferri pr^cipitatus. Edin. Precipitated Car-^bonate of Iron. Carbonas Ferri. Dub. Carbonate of Iron..

" Take of sulphate of iron, four ounces ,- subcarbonate of soda,

five ounces ; water, ten pounds. Dissolve the sulphate in the

water : then add the subcarbonate previously dissolved in the

water, and mix them together. Let the carbonate of iron, which is

precipitated, be washed with tepid water, and afterwards dried."

This preparation is also a subcarbonate of iron. By mixingthe solutions together, a double decomposition is effected; thesulphuric acid of the sulphate of iron combines with the soda,while the iron attracts the disengaged carbonic acid of the sub-carbonate of soda; and hence the products are an insolublesubcarbonate of iron, and a soluble sulphate of soda, which areeasily separated by washing and filtration. When first preci-pitated, the subcarbonate of iron has a deep green colour, and

1 Carmichael on Ihe Use of Carbonate of Iron in Cancer.

1 It is the carbonate of iron which is contained in chalybeate waters, heM in solutionbv the excess of carbonic acid. By exposing these waters to tiie air, the carbonic acidftiesoff, oxygen is attracted, and the carbonate falls down in the form of a yellowishsediment.

3 Chaiybs prseparatus e aceto, et sine aceto, P. L. 1720. ChaNbit nibign prapa-rata, P.L. 1745. Ferrirubigo, P. L. 1787.

LL 3