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phrey Davy, in his Bakerian Lecture for 1826, has produced several interesting facts of this class, with one kind of metal only: and several others are described in my pamphlet already alluded to, and are similar to some of those which Professor Schöenbein has met with, and enquired for an explanation.*
352. It may probably appear singular that I should compare Keir's experiments on iron, in which only one metal is employed, with another in which two are made use of. I therefore wish it to be understood, that on the surfaces of those simple metals which are active in any acid solution, the particles are as decidedly in different electric conditions as any two distinct metals can possibly be, and act voltaically on the liquid accordingly. Hence in an electrical point of view, each simple metallic body presents different electric surfaces, which are equivalent to a voltaic combination of two or more distinct metallic bodies. This once admitted, the inactivity of a metal, after some minutes immersion in an acid solution, follows as a matter of course, for the very same reason that two distinct metals become inactive after being some time in an active voltaic condition. Their relative electric conditions have suffered a change, and they become inactive in that particular liquid, though they would still be active in another; and a new pair of metals, or a new piece of a single metal, would also be active in the old liquid.
353. There are several experiments described, both in the Bakerian Lecture for 1826, and in my pamphlet, in which the metals employed have changed their electrical characters, and the currents change their directions accordingly. Iron is very susceptible of these electrical mutations. A combination of two pieces of iron, as nearly alike as they can possibly be made to appearance, will sometimes exhibit several mutations of this kind before they finally cease to produce a current. In their first condition they are active, and A is positive to B; in a short time they are neutral to each other ; afterwards B becomes positive to A, and becomes more and more so, till the needle indicates the maximum of action. The action again declines, and again they pass through the neutral point, and again A becomes positive to B. And after several mutations of this kind, the needle indicates that the two pieces are so nearly alike in their electrical characters that they are unable to produce an appreciable current. But agitation in the old liquid, or immersion in a new one, again brings them into a state of electrical activity.
354. Similar electro mutations, and final neutrality, take place on the surfaces of single pieces of metal.
355. There are different causes for metallic bodies changing their electrical characters by voltaic action, all of which will be found in the attachment of one or more of the constituents of the liquid employed. Hence the attachment of oxygen, nitrogen, metallic particles, &c., to metallic surfaces, will change the electrical character of them, and in many cases completely neutralize them, as regards particular li
Philosophical Magazine, for February, 1837, p. 133-4-5.
quids, though they may still be sufficiently active in other liquid bodies. Hence the voltaic energies on the surface of gold and platinum are too feeble to decompose any of the simple acid solutions, though sufficiently powerful to become active in their well-known solvent.
356. The particles of the liquids, and of their constituents, have also their electrical influence in all voltaic actions, and are electrically modified as decidedly as the surfaces of solid metallic bodies.
357. In all cases where simple metals are first active and afterwards inactive in acid solutions, it should be borne in mind that before they become inactive they are absolutely in metallic solutions, by the dissolution of a portion of their own substances. Hence in those experiments by Bergman and Keir, the cases were precisely alike, whether the iron was immersed in an already prepared metallic solution, or immersed into nitric acid only. And the more modern experiments with bismuth, &c., are of precisely the same character; and their inactivity, produced by the re-attachment (precipitation) of their own previously dissolved metallic particles, which give a new electrical character to the surface, and thus reduce the voltaic energies too low to remain any longer active on that particular liquid, though still sufficiently active to operate on a different one. Hence the cause of their brightness during their apparently inactive state : for in reality no metal is perfectly inactive when a fluid is presented to it suitable for a display of its voltaic energies.
358. With respect to other phenomena in the display of which only one individual piece of metal is employed, as first shown by Keir, they remain without even an attempt at explanation by any of the philosophers under whose notice they have appeared. Sir John Herschell pronounces them as of an “ extraordinary character ;''* Professor Andrews, after giving some very satisfactory explanations of several phenomena, acknowledges that he can offer no explanation of most of the particular facts which have been described ;"7 and Professor Schöenbein has not yet made public any explanation of them whatever. I
359. Under these circumstances it would be impossible to form any correct idea of the nature of the theoretical views on this subject which Professor Schöenbein will offer to the British Association at the Glasgow meeting. If, however, that philosopher should honour me with an attentive perusal of those facts and theoretical explanations to which I have already solicited the attention of the Association, it is possible I think that he will be enabled to find an easy and natural explanation to every phenomenon hitherto developed in this peculiar class, the whole of them being traceable to those laws,
Philosophical Magazine, for October, 1837, p. 333.
An abstract of Herschel's and Schönbein's experiments will appear in our next number.- Edit.
which, though many years before the public, he may probably till now, never have had an opportunity of becoming acquainted with.
360. I have shown that zinc, which is the most energetic metal in dilute sulphuric acid, may have its action either partially or totally annihilated in that liquid by the contact of copper wires ;* and I have shown that amalgamated zinc is perfectly inactive in solutions of sulphuric acid,t but that it is still active in solutions of nitric acid. These are cases in point, and the latter is of precisely the same character as those shown by the iron in Keir’s experiments. In one liquid it is inactive, in another it is active.
361. The explanation in these and in all similar cases, is referable to the difference of voltaic action in the solid and fluid bodies employed.
Practical Science, Manchester.
Note.—The contents of this Memoir were reported in the volume of the “Proceedings of the British Association for the Advancement of Science, for 1840,” in the following manner :
On a peculiar Class of Voltaic Phenomena, by Mr. Sturgeon.“The author directed attention to some experiments published by himself in 1830, and to his theory respecting the electro-chemical action of the simplest metals on acid and other solutions. He stated that the fact of iron not precipitating copper from its sulphate and other solutions, as recently observed by Professor Schöenbein, was one of the many beautiful phenomena discovered by Keir, and published in the Philosophical Transactions for 1790."
On the Theory of Voltaic Electricity. 362. Perhaps there is no individual branch of physical science that has exercised the ingenuity of philosophers to a greater extent, repecting the modus operandi whence emanates its diversified phenomena, nor has any one been more productive of diversity of opinion, as a theoretical topic, than voltaic electricity, from the first days of its discovery to the present time: and what may, perhaps, be considered still more remarkable, no theoretical discussion has been less successful in uniting the opinions of scientific men, so as to give a general sanction to any theoretical views that have hitherto been taken, from whatever quarter they may have emanated, than that wbich has proceeded from this subject, and which has now been continued through a long series of years, and still remains as undecided as at first.
• See my Experimental Researches, fc., experiments a and B, p. 78-79. † lbid, p. 41-42 -74–76–77. Ibid, p. 43.
363. Under these circumstances, therefore, any attempt that can be made, in this place, to elucidate the principles of a science in which the efforts of the highest minds have failed to produce a satisfactory explanation, will necessarily appear under great disadvantages, with every probability of suffering the common fate of its predecessors. But as there are some points on which philosophers entertain the same opinion, there is still a possibility, at least, though the attempt may be viewed in the character of a forlorn hope, of simplifying some others, so as to be sufficiently comprehended to gain general assent, and thus advance us one step farther into the apparent intricacies of the theory of voltaic electricity,
364. I believe that there is no difference of opinion, *at the present day, respecting the identity of the agency in common electricity, and that which is productive of the phenomena in that branch of physics now under contemplation: hence it is that we are not misunderstood by the term voliaic electricity, when represented as a peculiar branch of electrics. The generality of writers, however, on these matters, make no distinction whatever between voltaic electricity, and galvanic electricity; or, in other words, between voltaism, and galvanism, although the sources from which the phenomena emanate are as distinct from each other, as that of the phenomena of ordinary electricity is from either of them. Why this practice is not yet abandoned would not, perhaps, be easily determined; but it must proceed either from an ignorance of their distinction, from an unwarrantable proneness to confound the one with the other, or from a fear of stepping counter to custon, and thus avoiding the imputation of pedantry.
365. I am of opinion, however, that the omission of even a pointed distinction in “voltaic electricity," and "galvanic electricity," by writers of the present day, is not only a dereliction of duty towards their readers, who purchase and read their works under the impression of finding in them expressions of the clearest ideas that the science is capable of admitting, but the practice is fraught with the seeds of misconception and error. Therefore, whatever risk may be run on the score of pedantry, it is quite time that the pratice of confounding the two sources of electric action with one another were laid aside, and that distinction resorted to which alone can lead to clear and unequivocal views, and facilitate the association of ideas with the true character of the source of action.
366. In the preface to Aldini's “ Account of the late improvements in Galvanism," published in the year 1803, we find that the distinction between voliaism and galvanism would appear to be very clearly pointed out :-"A just tribute of applause has been bestowed on the celebrated Professor Volta, for his late discovery, and I have no desire to deprive him of any part of that honour to which he is so justly entitled; but I am far from entertaining an idea that we ought on this account, to neglect the first labours of Galvani. Though these two philosophers pursued different routes, they concurred to throw considerable light on the some points of science : and the
question now is, to determine which of them deduced the most just consequences from the facts they observed, and then to ascertain whether the facts established by Galvani led to the theory of Volta, or whether those discovered by Volta are connected with the theory of Galvani. For my part, I am of opinion that these two theories may serve in an eminent degree to illustrate each other.
"Last year Professor Volta announced to the public the action of the metallic pile. I here propose to exbibit, according to the principles advanced by Professor Galvani, the action of the animal pile.” And again, “In the first part of this work, I shall exhibit the action of galvanisin independently of metals, and explain some of its general properties.”
367. It is singular enough, however, that Aldini, who was the nephew of Galvani, and who laboured hard to show the distinction of the sources of galvanic and voltaic electric action, should eventually merge the one in the other, and call a series of " eighty plates of silver and zinc,” a “galvanic pile.”*
368. The distinction between the sources of galvanism and voltaism, is very marked, and susceptible of clear and unequivocal definition. The former being either a natural or an artificial association of animal matter, whether alive or dead : whilst the phenomena of voltaism emanate from associations of metals and other inorganic bodies. Galvanism, therefore, comprehends all those phenomena developed by animal electricity, and voltaism comprehends those developed by the simple contact of inorganic bodies, whether solid or fluid.
369. The electrical organs of the Torpedo and Gymnotus Electricus, and the muscular and nervous systems in all animals, are natural associations of animal matter, constituting sources of galvanic electrical action; and are as decidedly galvanic arrangements as are the artiGcial piles of muscle and brain first arranged by M. La Grave, and shown to the Galvanic Society of Paris : and afterwards operated with by Aldini, and various other philosophers.
370. In most of those electrical arrangements of inorganic matter hitherto formed, one, at least, of the bodies employed, has been a metal, and an association of two metals is invariably employed in every arrangement from which much action is derived. But it must not be considered from the hitherto invariable practice of employing metals in voltaic electrical arrangements, that electric action is not derivable from associations of non-metallic bodies; for it is well known that charcoal will supply the place of a metal, and it may easily be shown that the contact of liquids alone will produce electric action. These and all other associations of inorganic matter are sources of voltaic electricity.
371. With respect to the mode of action in voltaic associations generally, since the whole of that action is acknowledged to be electric, the principles of electricity, properly applied, are conse
See Aldini's work, page, 218.