L. Observations on Some Peculiar Properties Acquired by Plates of Platina, Which Have Been Used As the Electrodes of a Voltaic Battery

Philosophical Magazine Series 3

ISSN: 1941-5966 (Print) 1941-5974 (Online) Journal homepage: http://www.tandfonline.com/loi/tphm14

L. Observations on some peculiar properties acquired by plates of platina, which have been used as the electrodes of a voltaic battery

Golding Bird M.D. F.L.S. F.G.S.

To cite this article: Golding Bird M.D. F.L.S. F.G.S. (1838) L. Observations on some peculiar properties acquired by plates of platina, which have been used as the electrodes of a voltaic battery , Philosophical Magazine Series 3, 13:83, 379-386, DOI: 10.1080/14786443808649597

To link to this article: http://dx.doi.org/10.1080/14786443808649597

Published online: 01 Jun 2009.

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Download by: [University of California, San Diego] Date: 26 June 2016, At: 07:29 Dr. {3. Bird on certain Properties of Platina Electrodes. 379 tive or negative divergence. The discharge took place in both my cases on a leaf of writing paper moistened with distilled water, which was applied to the inferior plate of the condenser, while another leaf of moist paper covering the upper plate was touched with the fingers in order to make everything alike on both sides with respect to the condenser. The most simple form of the experiment might however be this; that a zinc condenser plate should be immediately touched with the moist fingers, which, as others have already observed, is sufficient to produce a negative shock. I do not say that this experiment is as yet explained agreeably to the contact theory, but as little could any one find in it a proof of the chemical theory. More- over, this may be viewed in connexion with other much more important experiments which promise at least a partial explanation of it, of which, however, it is not now my intention to treat.

L. Observations on some peculiar Properties acquired b2/ Plates of Platina, which have been used as the Electrodes era Voltaic Batter u. By Gor,nI ~r~ BIRD, M.D.F.L.S. t:. G.8., dyc., Lecturer on Natural Philosoloh2/ at C_vu2l's Hospital. HE influence of platina positive electrodes in effect- T ing the combination of oxygen and hydrogen are well known to philosophers ; some pheenomena which may be probably referred to the same class have lately fallen under my notice, and are interesting from their appearing to prove that metals which have served as electrodes retain a polar state long after connexion with the battery is broken. It was stated some time ago in a philosophical journal that when the platina plates of the ordinary apparatus used tbr ex- hibiting the decomposition of water by voltaic electricity on the lecture table, were placed in conducting communication with a piece of zinc immersed in the acidulated water with which the apparatus was filled, the hydrogen evolved at the surface of one plate was twice the volume of that given off at Downloaded by [University of California, San Diego] at 07:29 26 June 2016 the other. The author of this statement added that he was unable to give any explanation of the fact, nor did he offer any remarks upon it. This ph~enomenon appeared to be of sufficient interest to deserve a more extended examination, and I have had the pleasure of observing several curious facts in connexion with it. Exp. 1. A glass basin was furnished with two equal sized plates of platina passing through its bottom 1 "5 inches apart, each connected by copper wires to a brass cup for holding S80 Dr. G. Bird on certain Pro2erties acquired b9 the mercury; these cups, and the platina plates connected with them, may be called respectively A and B. The basin was filled with dilute sulphuric acid, and a tube full of the same fluid inverted over each plate of platina ; a rod of amalgamated zinc, to one end of which was soldered two thin copper wires, was immersed in the contents of the basin, and the ends of the wires dipped into the cups of mercury A and B, by which the rod became metallically connected with the platina plates. Rapid decomposition of water instantly commenced, bubbles of hydrogen being evolved from the platina surfaces: in five minutes the tubes were examined, and instead of the gas collected being in equal volume in either tube, as would d Triori be expected, I found, as stated by the original observer, that one contained nearly twice as much as the other. Upon reflecting on this experiment, I suspected that as the apparatus had been employed as a volta-electrometer a short time previously, the platina plates might have assumed and retained some peculiar state from their connexion with the battery. Exp. 2. The basin filled with the dilute acid was connected with a battery of six alternations of zinc and copper, separated by jars of porous earthenware and excited by sulphate of copper and sulphate of soda; the cup A was connected with the negative, and B with the positive wire : decomposition of water was allowed to proceed for a few minutes, contact was then broken with the battery; the tubes filled with dilated acid were inverted over the respective plates and the amalgamated zinc immersed in the acid, its wires dipping into A and B. Hydrogen was copiously evolved at the surfaces of the platina, and in 10 minutes the zinc was removed. In the tube over the plate Awas collected 1" inch hydrogen. B 2'15 --~ During the evolution of gas, the difference in the appear- ance of the bubbles from the two plates was remarkable: those from the plate B were large, rose rapidly to the top of the tube, and were given off from isolated points of the electrode ;

Downloaded by [University of California, San Diego] at 07:29 26 June 2016 whilst those from A were small, rose much slow~er in the tube, and were given off from every part of the plate, re- sembling the bubbles of oxygen evolved in the voltaic decomposition of water. It is remarkable that the platina plate (A), which when in connexion with the battery gave off tbe great- est volume of gas, (hydrogen) now evolved the smallest, and that (B), which had evolved the smallest (oxygen), now gave off twice the volume of the other. It is needless to state that the gas in both tubes was hydrogen. Exp. 3. Tile apparatus was refilled, again connected with Platina Electrodes of a Voltaic Ballerzj. 881 the battery, the plate A to the positive and B to the negative for a few minutes; ttle connexions being broken, the zinc rod was immersed as in the last experiment, its wires dipping into the cups A and B ; hydrogen was again evolved and collected in the tubes. In that over the plate A was found 2"1 B 1"o These experiments clearly pointed out, that the cause of the difference in volume of evolved hydrogen was to be sought in some change produced by connexion with the battery; what that change consisted in was less obvious. I suspected that a polar state might probably have been communicated to the electrodes by the passage of the battery current. Exp. 4. The cups A and B were again connected with the battery, A with the negative, B with the positive wire for a few minutes; the connexions were then broken, and a galvanometer of very delicate construction connected with the cups. The needles instantly deviated with considerable velocity to fl0 ° ; the connexion was broken, and in 1 minute renewed with the galvanometer; the needles deviated to the same amount but with less velocity. In 3 minutes, contact being again made, a deviation of" 85 ° ensued, and in 13 minutes the experiment was repeated and a deviation of only 4 ° took place. Exp. 5. The cup A was connected with the positive and B with the negative side of the battery during 8 minutes, and then the connexion was broken. On dippingthe galvanometer wires into A and B, deviation of the needles to 90 ° ensued as in the last experiment, but in the opposite direction. In both experiments, that platina plate which had been in connexion with the negative side of the battery and had then evolved hydrogen, appeared to be positive, deviating the galvanometer needles in the same direetion as a piece of zinc. The galvanometer made use of was extremely sensible, with light and nearly astatic needles suspended by a few fibres of unspun silk: the coil consisted of' about 600 convolutions of well mmealed and insulated copper wire wound on a frame

Downloaded by [University of California, San Diego] at 07:29 26 June 2016 on Nervander's construction. The frame being moveable on its axis could be brought into any position with regard to the needles. The temporary polar condition assumed by platina electrodes after connexion with the battery has been before pointed out by De la Rive and other physicists, a rationale has also been proposed for it by Becquerel (Traitd de l'Elec- tricite, &c. 3. 109). This philosopher has only mentioned the case when the electrodes have been immersed in a saline solution, and after the contact with the battery is broken, con- 382 Dr. G. Bird on eertaln Propertles acquired b9 the nexion made with the galvanometer; the deviation of the needles produced he attributes to minute films of aeid and alkali adhering to the electrodes, combining to re-form the salt electrolyzed by the previous passage of the battery current, and thus give rise to a weak secondary current in a direction the reverse of that of the battery. This explanation will, I think, hardly apply in the above experiments, as the electrolyte was dilute sulphurie acid, and no other elements present, separable by the electricity, whose reunion could ex- cite a current except oxygen and hydrogen; and even if the polar state be attributed to the previous decomposition of in- finitely minute quantities of saline matter accidentally present, still it would require more satisfactory evidence than we yet possess to show that the recombination of the separated elements of the salts would develop sufficient electricity to act with such energy on the galvanometer, particularly as the late experiments of Dr. Mohr, of Coblentz, have rendered it very doubtful whether electric currents are ever set in motion during the combination of an alkali with an aeid except inthe solitary case of nitric acid, and which then may, perhaps, be attributed to a very different cause *~. For the purpose of discovering some clue to the cause of this curious phamomenon, the following experiments were Fer- formed. Exp. 6. The cup A was connected to the negative and B to the positive wire of the battery ; tile connexion being removed, the deviation produced by connecting A and B to the galvanometer was ascertained to be 90°: the glass basin was then emptied of its acid, and set aside for 48 hours; at the expiration of that time it was refilled with dilute sulphurie acid and connected, again with. the galvanometer;. the needles deviated to 6 ° m the same direction as m Exp. 5. Exp. 7. The galvanometer wires being removed, the amalgamated zinc rod was immersed in the acid contained in the basin, its two wires dipping into the cups A and B ; gas was as before evolved from both platina plates; this was collected

Downloaded by [University of California, San Diego] at 07:29 26 June 2016 in separate tubes and measured. inches. In the tube over the plate A was found 1"95 gas = 1'0 B 2'~0 ~ = 1"18 Exp. 8. The cups A and B were connected with the battery as in Exp. 6, for five minutes ; the apparatus was removed ti~om the battery, and set aside for 48 hours full of the acid. On * "Ueber Becquerel's Einfache Kette, deren Strom aus dem Verbin- dung yon Siiure und Alkali enstehen soll."--Von Dr. Mohr, Poggendorf, .4nnalen, xlii. p. 76. Platina ;Electrodes of a Voltaic Battery. 383 then making a communication with the galvanometer, the needles moved to 30 °. Exp. 9. The galvanometer being removed, the zine rod was immersed as in Exp. 7, and the hydrogen given off collected in separate tubes. In the tube over plate A was found 4"20 inches = 1"0 B.-- 5"15 ' = 1"23 Exp. 10. The cup A was connected to the negative and B to the positive side of the battery : decomposition of water was allowed to proceed for 5 minutes; the wires were thenre- moved, the basin emptied of its contents, and repeatedly rinsed out with cold water. It was then refilled with dilute sulphuric acid, the rod of amalgamated zinc immersed, its wires dipping into the cups A and B: the hydrogen evolved was collected and measured. In the tube over the plate A was found 1"3 inches -- 1"0 B -- 1'7 = 1"3 Exp. 11. The basin of the apparatus was filled with the dilute acid, connected with the battery for 20 minutes, emptied, washed out with cold water, refilled with acid and connected with the galvanometer ; again placed in communication with the battery for the same time, emptied, and washed out with boiling water: this was repeated, the plates of platina being washed with a solution of potass, and in a fourth experiment with nitric acid; the basin being always refilled with the same dilute sulphuric acid before being connected with the galvanometer. The deviations produced were-- After washing the electrodes with cold water ...... 80 ° boiling water ...... 73 ° solution potass ... 4~5°

-- .... nitric acid ...... • ew 4 ° Exp. 12. The basin of the apparatus was filled with a solution of pure potass, sp. gr. 1"064 and connected with the battery during 5 minutes as in the preceding experiments. On then dipping the galvanometer wires into the cups A and

Downloaded by [University of California, San Diego] at 07:29 26 June 2016 B, the needles deviated to 45 °. The basin was then emptied, washed out with cold water, and refilled with the alkaline fluid: on making connexion with the galvanometer, the needles only indicated 5 ° . Exp. 13. The basin filled with the solution of potass was again connected with the battery as in the last experiment; it was then emptied, filled with dilute sulphuric acid and connected with the galvanometer : the needles instantly deviated to 90 ° with considerable velocity. In all these experiments the direction of the deviations was S8¢ Dr. G. Bird on certain Properties acquired by the constant; the plate of platina, which had during connexion with the battery evolved hydrogen, always being positive, and acted on the galvanometer like a piece of zinc. No appreciable difference in the surfaces of the platina plates with regard to lustre, &c., was observed. From the results of these experiments, we are, I think, hardly warranted in supposing with Becquerel, that the polar state of the plates arose from a film of acid and alkali adhering to them, although in other cases that this may be the cause of the polarized condition of the electrodes no one who has read the remarks of this distin- guished philosopher on the battery of constant currents can doubt (Traite, 5.219.), and perhaps Exp. lS may admit of an explanation of this kind. The fact of the polar state being to a great extent retained after washing the plates with water, alkalies, exposure to the action of acids for 48 hours, &c., is certainly opposed to the hypothesis of Becquerel, although I am aware that films of sulphurie acid cannot be entirely removed from plates of platina by washing, as Dr. Faraday has satisfactorily shown. The direction of the secondary currents, being opposed to that of the battery currents, appeared at first to connect these pheenomena with those of electro-dynamic induction. The fact of the secondary current being continuous for some time and gradually disappearing, instead of being only of momentary duration, might be supposed to arise from the badly conducting nature of the fluid connecting the plates of platina ; this hypothesis, suggested by some experiments, was at once refuted by the secondary currents being detected by the galvanometer, after emptying the glass basin and fiiling it withfresh dilute acid. The cause of the evolution of a double volume of hydrogen from the positive plate is less mysterious, this being evidently analogous to the ph~enomena observed by Dr. Faraday in his researches on the action of platina plates in effecting the combination of oxygen and hydrogen gases ; he found that the plates which had served for positive electrodes were very energetic in producing this combination, whilst the negative

Downloaded by [University of California, San Diego] at 07:29 26 June 2016 electrode was quite inactive, and this difference he attributed to the surface of the positive plate being more polished, and freer fi'om foreign matter than the negative. This view was confirmed by the fact of the negative plates becoming active by mechanically cleaning them. In the same manner I con- sider that the positive plates when connected metallically with file zinc rod, evolved a larger volume of hydrogen in a given time than the negative, because their surfaces were per- tiectly free from accidental tarnish, which although not readily appreciable by the eye, yet materially affects their electrical Plalina Electrodes of a Voltaic Batter9. 385 condition. On this hypothesis tile results of the other experiments may be explained: thus the volumes of gas evolved from the plates became more equal after the platina had been exposed to the action of those agents which would tend to re- move superficial impurities (Exp. 9, 10, &c.) ; and the intensity of action on the galvanometer appeared to be connected with a similar state (Exp. 11,) as the electric condition of the plates became nearly equal, after washing them with nitric acid, a deviation of only 4 ° taking place. What the substance is, whose invisible deposition on the negative plate causes this current, is conjectural; that it is not an alkali, as Becquerel has suggested, is I think proved by the positive electrie condition not being removed by dilute sulphuric acid, as well as from the almost infinitesimally minute quantity of saline matter present in the electrolyte employed in my experiments. That a very small quantity of foreign matter is sufficient to produce a very considerable action on the galvanometer is proved, by using for these experiments the dilute acid that has been previously employed for the generation of gas from the amalgamated rod, instead of fresh portions of that fluid ; the minute and imperceptible portion of zinc reduced on the negative electrode producing most intense action on a very delicate galvanometer. The negative plate I found became capable of evolving as large a volume of gas as the positive electrode, by scouring it with nitric acid and fine sand, evidently proving its former comparatively inactive state to depend upon some superficial deposition; the same result was obtained by employing both plates simultaneously as positive electrodes. Exp. 14. Two copper wires were for this purpose screwed upon the last copper plate of the battery, an end of each dipping into one of the cups A and B, the wire from the last zinc plate dipping into the dilute acid in the basin; under these circumstances both platina plates evolved oxygen, and were of course positive electrodes. On then breaking battery connexion and dipping the zinc rod into the acid, its wires

Downloaded by [University of California, San Diego] at 07:29 26 June 2016 being immersed into the cups A and B, equal volumes of gas were evolved, cwteris Taribus, fi'om both plates. From the results of this investigation I think I am justified in referring all the phamomena observed to the peculiar condition of surface assumed by the platina plate that has served as the negative electrode, its inactive state quoad the evolution of hydrogen, and its active state quoad the galvanometric current, depending upon one and the same cause, viz. the deposition of infinitesimally minute portions of foreign matter on it, which serves to diminish the rapidity of the evolution of Phil. Mag. 8.3. Vol. 13. No. 83. Nov. 1838. ~ C 386 Geological Sociely. gas at its surface, whilst, in consequence of its being attacked and ultimately dissolved by acids, it causes the platina plate covered by it to assume a positive state, and act as such upon a delicate galvanometer. That the substance deposited is not an alkali, or anything very soluble in water or acids, has been, I think, quite proved ; perhaps it may differ according to the nature of the electrolyte employed. ~B, Wilmington Square, Sept. ~9, 1838.

LI. Proceedings of Learned Societies. GEOLOGICAL SOCIETY. [Continued from p. 310.] June 6th.~A paper was first read, " On Spirofinites in Chalk and Chalk-flints ; " by the Marquis of Northampton, F.G.S. The fossils described in this memoir were chiefly found in the flints of Sussex; and though above two hundred specimens, more or less perfect, have been discovered by the author in that county, he has vel3r rarely met with the genus elsewhere. They have been also found in the same county by the Rev. G. Smith and Mr. Wal- ter Mantell. They occur more frequently in the grey than the black flints; and are sometimes accompanied by innumerable minute frag- ments of other organic bodies. The size of the best-preserved specimens, including the prolongation, is about one.third of an inch ; and the number of chambers or divisions varies in the same species. Of the six species described in the paper, one had been previously named, by Mr. Mantell, Spirolinltes Comptonl, and the other five have been named by the Marquis of Northampton, S. Murchisoni, S. Stokesii, S. Lyeltii, S. Mantellii, and S. J~ucktandii ; the author, however, stated that it is exceedingly difficult to determine satisfactorily specific differences, especially in such minute fossils, imbedded in flint, and exposed only by accidental fracture. A communication was next read, entitled, "A Note to accompany Specimens of Quicksilver Ore from the mine San Onofre, near the town of E1 Doctor, Mexico." By John Taylor, Esq., Treas. G.S. Though quicksilver had been known for some time to exist in Mexico, yet few attempts had been made to ascertain to what extent, till the increased prices and demand induced the directors of the Real del Monte and Bolafios Mining Companies to have re- Downloaded by [University of California, San Diego] at 07:29 26 June 2016 searches made. Ores of that metal have, in consequence, been discovered and traced in districts very remote from each other; but Mr. Taylor confined his remarks to the locality at which the specimens presented to the Society were obtained. The ores of San Onofre are chiefly cinnabar, partly hepatic, but native quicksilver occurs, and native calomel. They are stated to exist in a regular vein, two or three yards in width, the gangue consisting of carbonate of lime, with sulphate of barytes, and a small portion of silex. It traverses a limestone hill of considerable height, 0and appears to have been worked in former times.