from the latter, and they remain deprived of it to the same degree. 5. Lastly. If the positive body be removed or discharged, the three electroscopes diverge as negative. By the contact of the system, during the influence of the positive body, which had increased the expansive power of the electric fluid over the whole, the quantity of electric matter which had retired from its anterior parts had passed into the ground; and now, when the influence of the positive body has ceased, this deficiency of electric matter becomes common to the whole system.

Having now, by this series of experiments, demonstrated the fundamental proposition, that an equilibrium of expansive power of the electric fluid may subsist, between two insulated bodies in mutual contact, with a difference in its density, or proportional quantity of electric matter, I come to my system of the electric states of zinc and copper, when, being insulated, they are in mutual contact, which system is founded on that proposition.

It is evident, that the electric fluid must be in equilibrium of expansive power on this group composed of zinc and copper; therefore, the difference observed in their electric states must proceed from a difference in the density of the fluid. Now the only hypothesis added in my system to this immediate conclusion from fact is this: that, during their connexion copper has the property of acquiring more vector than zinc, from that diffused in the ambient air; by which proportional increase of expansive power, the electric fluid on copper is in equilibrium with that on zinc, though with less density, or proportional quantity of electric matter. I have shown also in the above mentioned works, by deduction from experiment, that, when this influence of bodies on each other, by plus or minus of vector, has ceased by sufficient distance, each of them possess instantly, by the effect of the ambient medium, a quantity of vector, proportional to its quantity of electric matter; and thus it is, that the modifications produced by zinc and copper on each other while associated, and their effects on bodies brought into contact with them on the outside of their groups during their association, are converted into modifications of the quantity of the electric fluid itself.

After having treated here the theoretical part of the subject more fully than I had done (for brevity's sake) in my first paper given to the Royal Society, in order to be better understood on this subject, very important in natural philosophy, I return to the experiments concerning the analysis of the galvanic pile, to bring them here to the same point as they were at in that paper.

Having found, by the experiment related at the end of the first part of this analysis, that by increasing the size of the plates, the divergence did not increase in the electroscopes, I considered the manner in which a great number of small plates might be used. I thought then of having a hole in the centre of small plates, in order to thread them with silk in form of chaplets, alternating the plates

with equal pieces of Dutch gilt paper. Not yet having any but tinned iron plates for these trials, I formed two such chaplets, each composed of 140 groups, of 0.5 inch diameter, and in order to guard them against dust, I enclosed them in glass tubes: but I found, that, when the chaplets lay along the glass, the effect was diminished, and in order to prevent this defect, I took larger tubes, with metallic caps, through which, by screws, I kept the chaplet fixed in the axis of the tube; these screws, being on the outside in the form of hooks, served to link the chaplets together. Each of these small instruments acted immediately on the gold leaf electroscope, and, by hooking them together, the effect was doubled.

the

Î founded at that time, on this experiment, the plan of increasing power of the new instrument so as to produce the divergence of small metallic balls, especially by using zinc plates, which I knew then could be procured. For this purpose I thought of lessening the expense occasioned by the metallic caps for the glass tubes, by making much longer chaplets, and of suspending these in the form of garlands, to the ceiling of the room, by silk strings, bringing only wires from their opposite extremities to a proper place, where the apparatus of the small metallic balls should stand.

Such is the point at which I had arrived the 30th of May, 1808: and this object was much forwarded in my paper under the title of The Electric Column and Aerial Electroscope, delivered to the Royal Society the 7th of March, 1809; but the Committee of Papers not having ordered it to be published in the Phil. Trans., it will now appear in a more advanced state. The consequence of its

not appearing at the time it should have done is, that my electric column has lost the merit of novelty; for, by the communications of the minutes at the meetings of the society and the committee, it had attracted attention; and the sight of it, which I did not refuse, has made it sufficiently known to be already imitated. However, while its connexion with the analysis of the galvanic pile is not considered, its principle object is lost: and moreover, till the sticking of the small metallic pendula, when striking, was prevented, which I have obtained but lately, it could not be ranked among meteorological instruments. These particulars will be seen in my following paper. (To be continued.)

Researches on the action of the Alkaline Peroxides on the Metallic Oxides. Letter from M. Ed. FREMY to M. Pelouze.*

THE evident analogy which exists between iron and manganese would lead to the supposition that we may one day produce with iron all the compounds which have been obtained with manganese. It is for this reason that I have thought that it would be possible to form salts in which an oxygenated compound of iron would play

an electro-negative part, and which would thus correspond to combinations of manganic and permanganic acid with the bases.

The facts I am about to make known show, I believe, in a conclusive manner, that iron can give birth to bodies which are produced in the same manner as the manganates, and which present a striking analogy with this latter class of salts.

When we heat for a considerable time to a temperature of a bright red, a mixture of potash and peroxide of iron, we obtain a brown mass which, dissolved by water, gives a solution of a very beautiful red violet, and which possesses characters hereafter to be indicated. This compound may be prepared more easily and in a few minutes, by calcining at a very high temperature a mixture of nitre, of potash, and peroxide of iron; or still better a mixture of peroxide of potassium and peroxide of iron.

I have succeeded in reproducing this body by the humid method, by causing a current of chlorine to pass into very concentrated potash, holding in suspension the hydrate of the peroxide of iron.

This compound obtained by these different processes is of a beautiful violet colour; a great quantity of water decomposes it at length; it becomes insoluble in very alkaline water, forming then a brown precipitate, which dissolves easily in pure water, and gives a solu→ tion of a beautiful purple colour. It appears much less stable than the manganate of potash. Under certain circumstances it is decomposed at the ordinary temperature in peroxide of iron, which becomes precipitated in pure oxygen, which disengages itself; and in potash, which becomes free: the liquor is in this case completely discoloured. A temperature of 100° makes it undergo a similar decomposition, but which is instantaneous.

All organic matters decompose it: it is consequently impossible to filtre its solution.

Such are the different facts which I have proved, and which all tend to make us admit the existence of a body more oxygenated than the peroxide of iron. I have found it impossible hitherto to isolate this compound, for when we come to treat this red solution by an acid, when the potash is saturated, there is a disengagement of oxygen and a precipitation of the peroxide of iron. If the acid is in excess it dissolves the peroxide, and forms a salt of the peroxide of iron. In the memoir which I shall have the honour to present to the Academy, I purpose giving the analysis of these new compounds, which I found based on the complete decomposition which they undergo under the influence of a temperature of 100°, and which permits us to proportion the disengaged oxygen, and the peroxide of iron which is precipitated.

I shall discuss the different manners of considering their composition in examining whether we may admit in these bodies the existence of alkaline peroxides. I shall also make known the results which I have obtained by placing the other metallic oxides in the same circumstances.

As the bodies which form the object of my researches are of a delicate preparation, and the study of them ought to be of a prolonged nature, I have thought it my duty to take date, and to announce from to-day the first results which I have obtained.

On the Constant Voltaic Battery. By J. F. DANIELL, For. Sec. R.S., Prof. Chem. in King's College, London; in a Letter addressed to R. Phillips, Esq., F.R.S., &c.*

MY DEAR SIR, IN the Annales de Chimie et de Physique for December, 1841, there is a paper by M. Edmond Becquerel, entitled "Sur les piles à Courant Constant," upon which I beg your permission to make a few observations in the Philosophical Magazine. The object of the author is thus stated :—

"A l'époque actuelle, où l'on cherche de toutes partes à appliquer les sciences physiques et chimiques, et par conséquent l'action des forces électriques, aux arts industriels, je pense qu'il peut être utile de présenter succinctement l'exposé de toutes les recherches qui ont été faites pour obtenir des piles dont l'action soit constante pendant un certain temps." (Ann. de Chimie, tome iii, p. 436).†

In this opinion I perfectly concur; and it is for the purpose of rendering such an account more perfect that I desire to correct some misconceptions into which M. E. Becquerel has fallen, and which have the effect of greatly mystifying the origin of constant batteries. After stating the well-known defects of voltaic batteries of the common construction, in which the two metals are plunged into the liquid in the same cell; and the necessity of constructing batteries of constant action before they could be usefully employed in the arts, he proceeds to make the following comprehensive claim:"C'est mon père qui a donné le premier les principes sur lesquels est fondée la construction de ces piles et qu'a formé les premiers piles de ce genre." (Ann. de Chim. p. 437).‡

Now as I have claimed to be the inventor of "the constant battery" (which was so named by myself), and as the Council of the Royal Society have so far sanctioned this claim as to award me the Copley Medal for my invention; and as I have most undoubtedly worked out the principles of its construction by experiments and legitimate induction, without the slightest suspicion that M. Becquerel had preceded me in the investigation, I was naturally very anxious to examine the evidence upon which this assertion is founded.

From the Philosophical Magazine.

+"At the actual epoch, in which it is sought in all parts to apply the chemical and physical sciences, and consequently the action of electrical forces, to the industrial arts, I think that it may perhaps be useful to present succinctly the exposition of all the researches which have been made to obtain piles whose action should be constant during a certain time.”

"It was my father who gave the first principles on which the construction of these piles is founded, and who formed the first piles of this kind.”

Previously to stating this evidence, M. E. Becquerel makes some remarks upon the phenomenon which has been most inappropriately termed the polarization of the plates of a voltaic battery, of which his father, he observes, has given the simple explanation.

"Dans le passage d'un courant électrique à travers un liquide conducteur voici ce qui a lieu : quand le courant primitif traverse le liquide conducteur, des élémens acides sont transportés au pôle positif, et des élémens alcalins au pôle négatif; alors, en interrompant la communication entre les lames décomposantes (ou électrodes) et la pile, les deux lames se comportent vis-à-vis l'une de l'autre comme deux lames que l'on aurait plongées, l'une dans un faible dissolution alcaline, l'autre dans une faible dissolution acide: c'est-à-dire, qu'en les mettant en rélation avec un multiplicateur, il y aura production d'un courant électrique dû à la réaction des molécules acides ou se comportant comme telles, sur les molécules alcalines par l'intermédiaire du liquide: ce courant sera par conséquent dirigé en sens inverse du courant initial. Cet effet se manifeste toujours lorsqu'un courant traverse un liquide conducteur quelconque au moyen de deux lames métalliques. Cette polarisation des électrodes a donc lieu dans toutes les piles, lorsque les lames qui compose chaque couple plongent dans un même liquide et dans un même auge.' 437-8).*

(Pp.

This hypothesis, however, though it borders upon the true explanation, is not correct; for in my first paper upon "Voltaic Combinations" (Phil. Trans., 1836, p. 116), I have shown that the polarization of the plates, and the rapid decline, and final cessation, of the current in batteries of the common construction, is owing to the deposition of metallic zinc upon the conducting plates. This I at first ascribed to the deoxidating power of the hydrogen upon the oxide of zinc, but have since adduced evidence to prove it is owing to the direct electrolysis of the sulphate of zinc formed. The deposit I was able to detach from the platinum, upon which it had been precipitated, in plates of considerable thickness. This opposition of

"In the passage of an electric current across a liquid conductor observe what takes place; when the primary current traverses the liquid conductor, the acid elements are transported to the positive pole, and the alkaline elements to the negative pole; then, on interruping the communication between the decomposing plates (or electrodes) and the pile, the two plates act in opposition to each other, like two plates which are immersed, the one in a feeble alkaline solution, and the other in a feeble acid solution; that is to say, by putting them in connection with a multiplier, we shall have the production of an electric current due to the reaction of the acid molecules, or which act as such on the alkaline molecules by the intermediation of the water: this current will consequently be directed in an inverse direction to the initial current. This effect always manifests itself when a current traverses any liquid conductor whatever, by means of two metallic plates. This polarisation of the electrodes takes place then in all piles, when the plates which compose each pair are immersed in the same liquid and in the same trough."