Ferri Iodidum. Lond. Iodide of Iron

"Take of iodine, six ounces; iron filings, two ounces; distilled water, four pints and a half. Mix the iodine with four pints of the water, and add the iron. Heat in a sand bath; and when the mixture has acquired a greenish colour, decant the fluid. Wash what remains with the half pint of water, boiling. Let the mixed and strained solutions evaporate at a heat not exceeding 212°, in an iron vessel, that the salt may be dried. Keep it in a well-stopped vessel, access of light being prevented."

In this process the union of the iron and iodine is direct; and these two nearly insoluble substances form a most soluble compound. I have found the soft iron wire used for stringing pianofortes preferable to the filings; and as the iodine combines with a definite quantity, the operator need not be particular in the quantity, if the combination be aided by boiling. The evaporation of the solution may be conducted in a common Florence flask, which, as soon as the evaporation is completed, should be rapidly cooled by pouring cold water on it, broken to pieces, and the preparation instantly bottled and well corked. It is, however, preferable to preserve it in solution of the strength of three grains to the drachm; and it can always be maintained of the same strength, by keeping, in the bottle, a coil of soft iron wire.

Qualities. - Solid iodide of iron, when well prepared, may be obtained in masses of beautiful acicular crystals of an iron-grey colour, and faint metallic lustre; but its usual form is an opaque, crystalline mass, closely resembling crystallised masses of iron in appearance. It is extremely deliquescent; and as it becomes moist the iron, is oxidized, separates from the iodine, and a sesquioxide is deposited. This is also the case when the solution is exposed to the air; but the iodine set free acts upon the soft iron, and the iodide is again formed, so that the solution is always of the same strength, although a quantity of sesquioxide may accumulate in the bottle.

This preparation is a protiodide consisting of one eq. of iodine = 126.3+ 1 of iron = 28, making the equiv.= 154.3, or, in its crystallised state = 199.3, owing to the addition of five eq. of water: or 100 parts consist of 63.3 of iodine, 14 of iron, and 22.7 of water.1

The solution is decomposed by the strong acids, chlorine, the alkalies, ammonia, and their carbonates, by lime-water, chloride of calcium, bichloride of mercury, acetate of lead, and all astringent vegetable infusions and decoctions.

Medical properties and uses.-The extreme solubility of this compound, formed of two very active but little soluble bases, led me to introduce it to the notice of British practitioners, as a powerful therapeutic agent.2 It is rapidly carried into the circulation, and may be detected in the urine and other secretions, by testing them with chlorine and starch a short time after the iodide has been taken. It operates as a stimulant to the glandular system, whilst at the same time the iron supports and improves the tone of the habit. I have found it beneficial in scrofula in all its forms, chlorosis, atonic amenorrhoea, hysteria, secondary syphilis, and incipient cancer. In secondary syphilis, it may be combined with iodide of potassium; and in incipient cancer its efficacy is aided by the administration of iodide of arsenic at the same time. I have found it serviceable in atonic gastric dyspepsia, when combined with bicarbonate of potassa, and taken at the moment of admixture. The dose is from grs. iij. to grs. viij. or more.