isolated (in this case oxygen) be disengaged in a free state or combined with the metals. This is opposed to the opinion of Mr. Grove and of others, that water is more easily decomposed by the electric current if oxygen combine with the positive metal of the pile. At least, it proves no more than the general admission, that in the chemical combination of two bodies, there is a great quantity of electricity developed or absorbed.

In other respects, the current should have a certain degree of intensity for the production of ferric acid. I plunged two plates of cast iron into the solution of potash, and afterwards united them to the metals of one of Grove's simple piles; but, in consequence of the dimensions of the pile, the current was too feeble: there was only formed, in this case, a small quantity of ferric acid. On the positive plate, however, there was a portion of oxide, a fact which I have never observed with wrought iron, and which proves that, under these circumstances, cast iron has a greater tendency to oxidize than wrought iron.

In general, cast iron, especially that which affords ferric acid, is more soluble in acids than wrought iron, probably in consequence of the molicules of carbon which are intermixed with it, exercising a galvanic action upon those of the iron, and also augmenting their solubility, in the same manner as the impurities in commercial zinc render it more soluble than distilled zinc. It is possible this is the reason that cast iron in particular gives rise to the formation of ferric acid.

On the other hand, the augmentation of the intensity of the current, at least up to a certain degree, does not interfere with the formation of ferric acid. If two of Grove's batteries be united, and the current conducted into the solution of potash, ferric acid is easily and abundantly obtained by means of the plates of cast iron.

I consider, even, that this mode of preparation is preferable to that which I first adopted, for it is not necessary to put the solution of potash in contact with the argillaceous vessel, so that the solution may be kept more pure, and the vessel preserved from destruction, which always ensues in the other way.

This mode of preparation offers one slight inconvenience, which is, that a part of the ferric acid formed, is lost, by its reduction at the negative plate. But this slight loss is amply compensated for by the much greater quantity of acid which is formed at the positive plate. I have said, slight loss this as

A curious modification of this process consists in taking, instead of two plates of cast iron, one plate of cast and one of wrought iron. If these be united to the battery in such a manner that the oxygen shall be conducted to the latter, it will be disengaged in the form of gas; if the plates be now reversed, ferric acid will be formed.

sertion may appear surprising, for it may be thought that, as much ferric acid would be decomposed at the negative plate as was formed at the positive plate; but this is not the case, probably from ferric acid not being decidedly electrolitic. There is always more hydrogen disengaged from the negative plate than there is of iron separated, consequently there is more water decomposed than ferric acid.

On the other hand, in addition to the formation of ferric acid, there is also developed at the positive plate, under all circumstances, with a simple pile as well as with a battery, oxygen in the form of gas; but more, certainly, with the battery than with the pile. It is very possible, therefore, that, by a sufficient augmentation of the intensity of the current, oxygen gas only, and no ferric acid, may be obtained, even from cast iron.

This accessory disengagement of oxygen is unfortunate, as it prevents the determination of the composition of ferric acid by galvanism.

It is certain, in fact, that the quantity of oxygen conveyed to the positive pole, is the equivalent of that of the hydrogen developed at the negative pole. But, if the first were completely combined with the iron (whether transiently or permanently, would signify but little) the quantity of hydrogen developed would serve to estimate the oxygen in the ferric acid: the oxide of iron separated giving the proportion of iron.

But the disengagement of oxygen gas, and the uncertainty as to whether this was concerned in the formation of the ferric acid, precludes the possibility of employing this method of determination.

The extreme facility with which this acid is decomposed, prevented my attempting its isolation, or that of its salt. If this isolation be possible, it can certainly only be effected at a very low temperature.

In conclusion, I would suggest the probability, that ferric acid, which is formed, as is known, but only in small quantity, at a high temperature, may be found, ready formed, in nature; for instance, forming the colouring matter of the amethyst, in which recent analyses have, in addition to silica, discovered iron with a trace of manganese. Annalen der Physik und Chemie.

PREPARATIONS OF IRON.

BY M. BERAL.

EXPERIMENTS undertaken for the purpose of rendering more perfect the preparations of iron used in medicine, have led me to the discovery of several ferruginous products not yet studied,

or but little known. I shall make known the more prominent properties of these products, so as to complete what I have already published on ferruginous compounds in general, and on the citrates of iron in particular.

SESQUICITRATE OF IRON.

The citrate of the sesquioxide of iron is obtained in transparent laminæ, of a beautiful garnet hue*.

PROTOCITRATE OF IRON.

The citrate of the protoxide of iron is prepared by treating iron filings with citric acid previously dissolved in distilled water. This salt is white and pulverulent, and but slightly soluble. It is rapidly coloured by light, and by the action of moist air its composition is modified, the iron passing to a higher degree of oxidation. This citrate, like the other protosalts of iron, has a strongly marked chalybeate taste.

CITRATE OF THE MAGNETIC OXIDE OF IRON.

Combined with the magnetic oxide of iron, citric acid furnishes. an uncrystallizable salt, of a green colour, and susceptible of being formed into transparent laminæ. This salt is soluble and very active, but as its taste is decidedly chalybeate, it is on this account objectionable for internal use. It is remarkable, that its solution does not alter, but preserves its green colour, although exposed to the prolonged action of the atmospheric air.

CITRATE OF IRON AND QUINA.

The citrate of iron and quina is a new salt, which was required as a therapeutic agent. This medicine is formed by the combination of four parts of citrate of iron, with one part of citrate of quina. It is obtained in the form of transparent laminæ, soluble, very bitter, and of a garnet hue. This salt is best adapted for administration in the form of pills, on account of its great bitterness.

The iron in this preparation is in the state of the magnetic oxide united with an acid. It is soluble, tasteless, and susceptible of useful applications.—Journal de Chimie Medicale, 1840

The formula for its preparation has already been given.

THE ETHERS OF THE ORGANIC ACIDS.

BY M. GAULTIER DE CLAUBRY,

UNTIL the present time, it has been only in some of the inorganic acids and the acetic acid, that the property has been recognised of transforming alcohol into ether; the inorganic acids producing hydrated ether, and the acetic acid giving rise to acetic ether; besides this latter can only be formed by a succession of actions, the number of which depends upon the rapidity with which the operation is conducted.

With regard to the latter acid, there is some difference between the action of the crystallizable acid and that which contains a larger proportion of water.

In considering the nature of the action upon which etherification depends, I thought that if instead of distilling a mixture of alcohol with those organic acids which have hitherto been considered as insusceptible of directly forming ethers (that is, without having recourse to the intervention of sulphuric or hydrochloric acids, by which means compound ethers are obtained) that the acids be heated just to the point at which they begin to be decomposed, and the alcohol made to fall upon them in drops, the acid having lost its water, and being greatly in excess in proportion to the alcohol, would, in this case, determine the formation of ether. This, in fact, has been found to be the case with several acids.

The first on which I operated was the oxalic acid.

If oxalic acid be heated in a tubulated retort just to the point at which it begins to give out white vapours of the acid with only one atom of water, the alcohol, on being dropped in, is for the most part converted into ether, which distils over with a portion of unaltered alcohol. A large quantity of oxalic ether may be easily obtained in this manner.

The benzoic, succinic, and citric acids, also afford, under similar circumstances, a large proportion of ether. I have not yet determined whether that which is obtained from citric acid be the citric, itaconic, or aconitic ether. I am now engaged in investigating its real nature.

With the mucic, tartaric, gallic, and tannic acids, I have hitherto been unable to obtain conclusive results. The three last named ethers, however, have never yet been formed.

With regard to the oily acids, I have not yet succeeded in regulating the operation so as to obtain a definite result.

Spirit of wood, placed in the same conditions as alcohol, has not afforded me conclusive results. Is this in consequence of its greater volatility, or of its being more difficultly etherified? This I am unable at present to say, but I think it will be found easy to overcome the difficulties I have hitherto met with in regard to this body.-Comptes Rendus.

TO THE EDITOR OF THE PHARMACEUTICAL JOURNAL.

SIR,-The annexed table, drawn up for my own use from the best sources within my reach, may, perhaps, be acceptable to some of your readers. I trust it will be found sufficiently correct for all practical purposes; but should any material error have been overlooked, I shall be obliged to any correspondent who will point it out. I am, Sir, your obedient Servant, H. BEASLEY. Table of the Densities of Alcoholic Liquids employed in Pharmacy, shewing the corresponding degrees of the principal Areometrical Scales,

The numbers on Gay Lussac's scale denote the per centage, by measure, of absolute alcohol; those of Sykes's hydrometer the excess or deficiency, per cent., of proof spirit in the sample. The Batavian scale is 10 less than Baumé's throughout, water being 0 instead of 10.