The protoxide of iron has so powerful an affinity for oxygen, that it cannot remain an instant in contact with air, or water containing air, without undergoing a partial change into sesquioxide; and a brief exposure is sufficient to render that change almost complete. The same property is evinced when it is combined with acids, and especially with carbonic acid. Hence, as soon as the carbonate of the protoxide is precipitated from a solution of the mixed salts out of which it is formed, it begins to absorb oxygen, and give out carbonic acid, until, as explained in the foregoing article, it is almost wholly converted into sesquioxide.

Now it is believed that the protoxide and its compounds find a readier entrance into the system than the sesquioxide and its compounds; and the fact is beyond all doubt in relation to the carbonate, which experience has shown to be much more efficient, in bringing the system under the influence of iron, than the sesquioxide resulting from its exposure.

The difficulty, however, was to preserve the carbonate unchanged till it could be administered. It had been discovered that sugar had the singular property of impeding, if not preventing the oxidation of iron; and the idea suggested itself to a German physician of the name of Becker, that this property might be taken advantage of for medicinal purposes. The idea was carried into effect by Klauer, a German chemist, who prepared a carbonate of iron so protected by sugar that it resisted the tendency to sesquioxidation. M. Vallet, of Paris, improved the process; and hence, the preparation adopted by the U. S. Pharmacopoeia, and most used in this country, goes commonly by the name of Vallet's ferruginous pills.

Preparation

According to the U. S. process, sulphate of iron and carbonate of soda are dissolved in separate portions of sweetened water; the solutions are mixed in a bottle which they just fill, and which is well stopped to exclude the air; the precipitate of carbonate of iron thus formed is separated, and washed with sweetened water; and, lastly, having been allowed to drain, the mass is instantly mixed with honey and sugar, and evaporated to a consistence fit for the formation of pills.

The British Pharmacopoeia simply mixes the two salts dissolved in water, and, after washing the precipitated carbonate, mixes it with sugar, and dries at a heat not exceeding 212°. The preparation thus obtained is denominated Ferri Garbonas Saccharata (Saccharated Carbonate of Iron), and is converted into pill by rubbing with confection of red roses.

As the slightest exposure of the carbonate is attended with change, it is desirable that the protecting influence of the saccharine matter should be present in every step of the process; and that, until it is completed. there shall be no avoidable exposure to the air. These conditions are fulfilled in the U. S. process, adopted from Vallet; and the resulting preparation, therefore, is the unchanged carbonate of the protoxide simply incorporated with sugar.

In the British formula, oxidation is going on from the commencement of the process to the moment when the sugar is finally added; and consequently a considerable proportion of the carbonate is changed into sesquioxide. It is obvious, therefore, that, of the two preparations, that of the U. S Pharmacopoeia is to be preferred.

Properties

The U. S. preparation is a soft mass, of such a consistence as to be readily made into pills. It is black, of a sweet and strongly ferruginous taste, and readily and wholly soluble in muriatic acid, with brisk effervescence. The British preparation is a grayish-green powder, having a similar taste, and in like manner soluble in muriatic acid. The former consists exclusively of carbonate of protoxide of iron with somewhat more than half its weight of sugar; the latter has the Mom ingredients with an uncertain proportion of sesquioxide of iron.

Medical Uses

This preparation is little used for obtaining the direct effects of the chalybeates upon the primae viae, for which it is not adapted. But, in reference to its effects on the system, it is one of the best chalybeates, probably upon the whole inferior to none; being at the same time perfectly mild in its action on the stomach, which it very seldom offends, and readily and wholly soluble in the gastric liquids, and therefore absorbable into the circulation. Abundant experience has proved both its gentleness and efficiency. I have been in the constant habit of using it, and have always calculated, with the utmost certainty, upon the desired effects from it, so far as these might depend on the impregnation of the system. In the Pennsylvania Hospital there is a constant succession of patients, especially in the autumn, in the most pitiable state of anemic debility, often complicated with oedema of the limbs, to whom a dose of this medicine three times a day, with a little quintal and nutritious diet, in the course of from two to four weeks, and sometimes even a shorter period, restores healthy colour and Strength. Indeed, whatever can be accomplished by any one of the chalybeates towards improving the blood may be expected from this. There are others preferable for some special purpose, or on particular occasions from their solubility, or in reference to a direct action on the mucous membrane of the primae viae, but none, I believe, as a reconstructive agent, to build up a debilitated system by the restoration of red corpuscles to the blood.

The dose of the pilular mass is from three to ten grains three times a day. Five grains may be given in a pill without inconvenience. More than fifteen grains would be liable to produce irritation of the stomach or bowels. Of course, if continued so as to produce plethora, the medicine may occasion headache and other unpleasant symptoms.

There are two officinal preparations which may be most conveniently noticed here, because the aim in them, so far as their chalybeate ingredient is concerned, is to produce the carbonate of iron, though, from the deficiency of sugar, this undergoes a somewhat rapid change into sesquioxide. The preparations referred to are the Mistura Ferri Com-posita, and the Pilulae Ferri Composites of the U. S. Pharmacopoeia.

1. Compound Mixture of Iron. - Mistura Ferri Com-Posita. U. S., Br

This is prepared from sulphate of iron, carbonate of potassa, and myrrh, with spirit of lavender and a little sugar to flavour it, and rose-water as the vehicle. When freshly prepared, it is greenish, and may be kept so if perfectly excluded from the air; but the least exposure changes its colour, in consequence of the sesquioxidation of the protoxide of iron of the carbonate, which results from the mutual reaction of the two saline ingredients. A large addition of sugar would have a tendency to prevent this change. It is an imitation of the antihectic myrrh mix-lure of Dr. Griffith, which at one time had considerable celebrity. It combines the effects of myrrh with those of the chalybeates, and may therefore be given in anemic states of the system, with amenorrhoea, and chronic catarrh; but should never be administered in inflammatory conditions of the gastric mucous membrane. I have seldom found much benefit from it in phthisis, in which it was formerly employed. The dose is one or two fluidounces two or three times a day.

2. Compound Pills Of Iron. - Pilulae Ferri Compositae U.S

These pills are made with sulphate of iron, carbonate of soda, myrrh, and syrup sufficient to form a pilular mass. Carbonate of iron results from the double decomposition of the two salts, but by time and exposure is converted into the sesquioxide. The pills are no doubt useful as a tonic and emmenagogue; but, since the introduction into use of the pills of carbonate of iron, have no sufficient end to answer. Their intended effects would be better obtained by combining the latter preparation with myrrh, in such proportions as might seem best adapted to the particular occasion. The dose is from two to six pills, equivalent to about six and eighteen grains of the mass.

3. Natural Chalybeate Waters

These belong to the present head, as they generally owe their virtues to the carbonate of iron they hold in solution. Carbonate of iron is insoluble in water, but is dissolved by water impregnated with carbonic acid gas. Water which has been exposed to the air always contains a small proportion of carbonic acid, sufficient to enable it to dissolve a portion of the carbonate. Hence ordinary spring or river water, remaining long in contact with ores of carbonate of iron, would be more or less impregnated; but when waters highly carbonated are similarly exposed, they become of course much more strongly chalybeate. All chalybeate waters, when exposed freely to the atmosphere, gradually part with their iron; the protoxide of the carbonate being converted into the sesqui-oxide, which, being insoluble, and incapable of uniting with carbonic. acid, is deposited. Hence the yellowish-brown deposit in springs of this kind, and the track of a similar colour, which marks the course of a chalybeate streamlet The pure chalybeate waters act upon the system in the same manner as the officinal carbonate, and probably, from the dissolved state of the salt, with still greater facility. They are admirably adapted to produce all those beneficial changes in the system for which the chalybeates are generally given; especially when drank at their native sources in mineral springs, where they are often aided by the invigorating influence of pure air, exercise, and agreeable association. They may, however, be abused; and it is necessary to be cautious in their use in health, and not to continue them too long in debility, lest plethora should be induced, with its risk of hemorrhage and inflammation, or fever. The natural chalybeate waters appear to be occasionally diuretic, and are thought to have proved useful in chronic nephritic diseases.

Artificial chalybeate water may be made by dissolving a mixture of sulphate of iron and bicarbonate of soda in carbonic acid water. Tea grains of each of these salts, powdered and intimately mixed, and then dissolved in a tumbler of the water, will afford a lively drink, containing four grains of carbonate of iron, with a little sulphate of soda, and an excess of the bicarbonate. The whole quantity may be taken at once, morning and evening.