Iron wire is used in the Pharmacopoeia for the formation of the iodide, the sulphate, and the granulated sulphate; and when thus employed, should be soft or wrought iron, which is flexible and non-resilient. Ferrum Redactum. Reduced Iron. Metallic Iron in powder.
Synonym. Ferri Pulvis. Dub. Fer reduit.
Prep. Ordered to be made by reducing the peroxide of iron to the metallic state, by heating it in a gun-barrel in a furnace, and passing through it hydrogen gas, previously rendered dry by having passed over sulphuric acid and chloride of calcium.
Prop. & Comp. An impalpable powder, of a steel-grey colour, strongly attracted by the magnet, and exhibiting metallic streaks when rubbed with firm pressure in a mortar; it is soluble in dilute hydrochloric acid, with effervescence from the evolution of hydrogen, and the solution gives a light-blue precipitate with the ferridcyanide of potassium; it oxidizes when exposed to damp air: it should be pure iron, but it usually contains some magnetic oxide and a little sulphuret of iron. Ten grains added to an aqueous solution of 50 grains of iodine and 50 grains of iodide of potassium, and digested with them in a small flask at a gentle heat, leave not more than 5 grains undissolved, and this should be entirely soluble in hydrochloric acid: this test indicates that at least one-half of the powder is metallic iron, as the magnetic oxide is not dissolved by the iodine solution.
Therapeutics. Reduced iron may be given when we desire the blood-restoring properties of the metal without any astringent action. It is a powerful haematinic even in small doses. It usually sits easily on the stomach; but occasionally annoys by causing the evolution of sulphuretted hydrogen.
Dose. Of reduced iron, 2 gr. to 6 gr. It may be taken with advantage with a meal.
Adulteration. Reduced iron is very apt to contain some sulphuret, from a subsulphate being thrown down with the oxide. Occasionally magnetic oxide has been mixed with or substituted for the reduced metal; the former impurity can be detected by the evolution of sulphuretted hydrogen when an acid is added; the latter by the want of effervescence or non-evolution of hydrogen, and the quantitative test above given.