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made, the metal in solution became re. metals. Can we for a moment suppose that duced. Thus, when iron and silver were the slight negative and positive electricity, placed in a solution of copper, the iron im- produced by the contact of two small wires, mediately began to reduce the copper in which would not affect the most delicate solution, while the silver had not the slight- electrometer, can have the power, the one est action. Upon bringing the two metals of attracting oxygen, and the other hydroin contact, however, the silver became gen, at the distance of eighteen inches, coated with copper. Dr. Wollaston attri reckoning from the middle of the tube. butes the curious phenomenon, above de If the same tube be bent in the middle scribed, to a change of states in the electri to an acute angle, like the letter V, accity of the metals ; and in order to confirm cording to Mr. Davy's hypothesis, the this idea, he attempted the same by means appearance of the hydrogen at the silver of common electricity, in which he suc wire ought to take place as soon after the ceeded to his utmost satisfaction. He sup contact, as with the straight tube; but what poses that the chemical affinities are so alter is very singular, it will not take place at all. ed by the presence or absence of electricity, This experiment would seem to prove, that as to induce the anomalous appearances,
one of the constituents of the water is carwhich took place in the above experi. ried through the whole length of the tube; meuts. The silver wire became coated and that by some law which differs from with copper, and at the same time appeared those of electricity, since the angle of the to have the power of decomposing water. tribe appeared to interrupt its passage. The
The only mystery we observe in these ex- interruption is still greater, even with a periments, is the liberation of the hydrogen shorter tube, when the tube is bent in dif. in a situation where no oxygen is mani- ferent places, forming a sort of zig-zag. fested either in the form of gas, or in The idea that hydrogen is carried from any other state. Nor does the new doctrine, the zinc to the copper wire, is strongly falately advanced by Mr. Davy, throw much voured by anoth:er experiment. Take the light on this subject. The zinc in this ex. glass tube, AB, fig. 2, filled with dilute periment, is said to be positively electrified, muriatic acid, having a cork at B, through and the copper or silver to be negative. which the wires, z and c are passed, z beThat the zinc, on that account, attracts the ing a wire of zinc, and c a wire of platina, oxygen of the water, and the silver the hy. silver, or copper. So long as the wires redrogen. That the constituent parts of wa main unconnected at z, the platina-wire apter are by the same law made to appear in pears unchanged; but, as soon as the consituations where the decomposition did not tact is formed, bubbles of hydrogen are take place, is very evident; hence it would first seen at d; they then very slowly begin appear that the hydrogen is carried by to appear in the lower parts of the wire; but some means from the zinc to the silver. Or what is singular, the moment they begin to that the oxygen passes from the silver to the appear at f, they are also seen at s, and zinc, or according to Mr. Davy's hypothesis, some seconds are elapsed before any bubthe decomposition of the water takes place bles are seen at g. If the hydrogen in the between the metals, the oxygen passing last experiment were attracted by the neinevitably to the zinc, and the hydrogen in gative state of the platina-wire, since the a similar way to the silver. To the latter metal is the best conductor, it would seem, there are several objections, which will ap- that the point, s, would be the last part to pear from the following experiments. have parted with its electricity; and, of
Let a tube of three feet in length be course, the bubbles of hydrogen ought to filled with dilute muriatic acid, and corked have appeared the last at that point, which at both ends, having a wire of zinc inserted is contrary to fact. It therefore appears in one end, and one of silver or platina in more likely that the hydrogen has been the other. The zinc will immediately be held in combination by the electricity, the gin to give out hydrogen, but no effect will latter of which is taken by the nearest mebe observed at the silver wire. Leta com- tallic conductor in the circuit, leaving the munication be established between the hydrogen in its gaseous form: the law, how. wires on the outside of the tube. The sil- ever, by which it moves along the liquid, ver does not immediately give out bubbles, does not appear to agree with any known as was the case in the experiments of Dr. properties of electricity, since the hydrogen Wollaston, nor does that effect take place, is some seconds in reaching the point g. ull a few seconds after the contact of the It will appear, from the above experin VOL. III.
ments, that the galvanic phenomena are es bottle with a solution of acetate of lead, in sentially promoted, by having two metallic the upper part of which is suspended a surfaces so situated, that one shall be oxy piece of metallic zinc: in the course of a dated, and that the other shall be situated day or two, metallic lead is observed in as near it as possible, for the purpose of re shining filaments, suspended from the piece ceiving its electricity. We have shewn, of zinc. The same difficulty occurs in this, that the current is not only interrupted by as in the last experiment: the filaments of distance, but that it is essential the passage lead constantly grow from the ends at a disshould be a direct line.
tance of many inches from the zinc. In In Dr. Wollaston's experiments, when order to prove that this experiment is simi. the wires were placed in a metallic solution, lar to the last, that is, that the lead is re. such as that of copper and silver, and the duced by the hydrogen, take a tube, AB, contact formed between the zinc and silver fig. 5, at one end of which, tie a piece of wires, no hydrogen was evolved by the lat. bladder so tight that the tube may hold water, the contrary of which was the case ter; let a cork be inserted at A, through with the dilute acid; but the metal in solu which the platina wire, P p, is passed; the tion became redriced upon the silver. tube being set up right in the zinc cup, D,
There does not appear any thing myste- containing dilute muriatic acid, and a conrious in the reduction of the metal, since
nection formed at P, the platina soon bethe hydrogen does not appear, being em.
comes covered with brilliant crystals of meployed in the deoxydation of the metal.
tallic lead : bence it would appear, that the A further proof that this is the case, is, that platina had the power of reducing the lead no other metals can be reduced in this way,
into its metallic state, or that some subbut such as do not decompose water. This
stance had been transmitted through the singnlar process enables us to account for bladder adequate to that effect. If, instead several facts which have hitherto appeared of the acetate of lead, the tube be filled anomalous. If a glass plate be smeared
with dilute acid, upon the connection beover with a solution of nitrate of silver, and ing formed at P, the platina becomes coa common pin be laid in the middle of the vered with bubbles of hydrogen: need we, plate, beautiful ramitications of metallic, sił- therefore, hesitate in concluding, that the ver will soon appear, as if vegetating from lead owes its reduction to the hydrogen. the pin. If the process be examined by a The method of whitening brass and copmagnifying glass, the ramifications of silver per, by boiling them with cream of tartar may be fairly seen to grow from their ends.
and tin, is a process of this kind; the cream Though the more oxydable metal, the of tartar, and the metailic tin, answering pin, may, in the first instance, have reduced the purpose of the zinc and acetate of lead, a portion of silver, it does not account for in the last experiment: a portion of the tin the vegetative appearance which is after. in solution is reduced upon the copper or wards observed. The pin cannot reduce brass, rendering it white, by the hydrogen the silver at so great a distance from itself, which is produced during the galvanic conwhich is sometimes more than an inch. In tact of the copper or brass, with the tin. order to prove, that the agency of the oxy In all the experiments, the zinc wire is, dable metal was not essential to the reduc. during its contact with that of the platina, tion of the metal, the writer of this article silver, &c. undergoing an increased oxyda. covered one half of the plate with liquid ni. tion, which is proportionate to the quantity trate of silver, and the other half with di- of hydrogen evolved at the platina wire; lute muriatic acid, suffering the liquids to since the oxygen of that, and hydrogen, both touch each other; a wire of zinc was laid of which are derived from the water, are disin the dilute acid, and one of platina in the posed of in the oxydation of the zinc. The nitrate of silver. As soon as the opposite hydrogen passes from the zinc to the oppo. ends of the wires were brought in con site wire, with the greatest facility, through tact, beautiful ramifications of silver soon a direct liquid communication, the shorter began to appear from the platina wire, but the better. It becomes much interrupted no gas was observed.
by having to turn sharp angles, or in passing If a solution of gold be used, instead of through small apertures. It passes with that of silver, the platina becomes speedily more or less freedom through solid bodies, gilt. The experiment producing what is when moistened with water, but does not called the lead-tree, cannot be accounted pass at all, except when moisture is prefor in any other way: it consists in filling a
Having given an account of the effects warmed, are to be pressed down into the resulting from a single galvanic combina- grooves before the cement becomes quite tion, we will next give some account of the cold. After the plates have been insert. constructions of that compound apparatus, ed, in such order that all the zinc surtermed Galvanic, or more properly, the Vol. faces shall face one way and the copper the taic battery.
other, the cement must be more evenly The pile of Volta, of which we have al. adjusted with a hot iron which will reach ready given a slight description, is at pre- to the bottom of the cells; the trough being sent so little used, that we shall direct our laid first on one side and then on the other attention more particularly to the trough, for that purpose. as being more convenient for experiments When the cementing process is finished, than the pile, and at the same time less lia- and the whole sufficiently cold, the trough ble to be out of order.
must be dressed off and varnished with The wood of which the trough is formed, copal varnish where it can be had; but in should be the oldest and hardest mahogany, lieu of that with common spirit varuish. being less liable to warp than other kinds When the varnish is dry it must be polished of wood. The sides of the trough must be with rotten-stone and water. dove-tailed together, and the bottom ought In the above construction it is manifest to be grooved into the sides, and fitted-in that two of the surfaces are lost by being with turpentine; perpendicular grooves laid and soldered together. About two must be made in the sides of the trough, years ago the writer of this article had con for the reception of the plates, correspon- ceived the possibility of making use of both dent to which there must be grooves in the the surfaces of the copper and zinc plates bottom. When the length of a trough is at the same time. Accordingly he cementmore than two feet, it becomes unweildy; ed into a trough, in the groove made for it should not even be that length, when the the plates of metal, plates of glass. The size of the plates would render it too heavy metal plates were formed by soldering to. to be handed about. The distance between gether a plate of each, of copper and zinc, the plates should be about three-eighths of and then bending them till the plates bean inch; if they are nearer together, the came parallel to each other, leaving a space acid employed is too soon exhausted, and between the two surfaces a little wider consequently, the power of the battery less than the thickness of the glass plates. lasting.
The cells between the glass plates being The plates should be of copper and zinc. filled with the proper liquid, each of the Though silver is stronger than copper, it is above compound plates were made to benot so in proportion to the price.
stride one of the glass plates, in such order The zinc plates are best cut out of sheets that a zinc and copper plate of two differof malleable zinc, as being cheaper, less li. ent compound plates, in succession to each able to break, and may beused much thinner. other, may occupy each of the cells. All
The copper may be employed so thin as the surfaces are by this contrivance exposed six ounces to the square foot.
to the action of the liquid, and might be The plates of copper being made a little considered double the power of a common larger than the zinc, may be lapped over trough, having the same number of plates. the edges of the latter, by which means Little or no advantage was gained by they fit much closer to the zinc plate, with- this method. Though there are two surout the labour of hammering the copper faces of each metal in each of the cells, plates previously flat. The copper plates it will be evident, from several minor exonly require to be soldered to the upper periments already given, that two of the edge of the zinc plate, since the other three surfaces are so completely disconnected as edges are so secured with cement in the to produce litile or no effect. One of the grooves as to preclude the necessity of zinc surfaces in this trongh is facing the soldering. The lapping over of the copper glass on one side the cell, and one of the is sufficient to keep it close to the zinc copper surfaces is similarly situated on the plate till the plate is fastened in the trough, other side. Previously to inserting the plates in the The trough, therefore, which is repre. trough, the inside must be lined with a ce. sented in figure 1, and which has been par. meni, formed of resin and bees-wax, or what ticularly described, is, for general use, the is cheaper, of six parts of resin and one of most convenient, and in other respects, the lime and oil. The plates, being previously best battery yet introduced.
The next thing to be considered, is the square to that of ten ; the surfaces being as management of the galvanic battery. First, four to one hundred. The effect upon the all of the cells of the trongh must be filled, muscles, as well as upon the cuticle itself, within about half an inch of the top, with is very different from large plates, when the a liquid, composed of water, with about series is the same. It appears, that the one twenty-fifth part of the muriatic or the shock, or first impression, is as the series, nitric acid. The plates of the trough are which is also as the intensity of the electrishorter than the depth of the trough, by city. If the shock be received from the about three-fourths of an inch ; so that the same number of large plates, the same spetrough may be leaped on one side in the cies of commotion is produced in the first filling, for the purpose of letting the liquid instance, as with the small plates ; but if the run equally into all the cells.
contact be still kept up, a continuation of If a number of troughs are to be con the effect is perceived, which is felt through nected together, the communication must the whole arms, producing a vast tremor, be made by arcs of metal, which are in attended with a sensation of warmth. If serted into the liquid of one cell of each the plates be from eight to twelve inches trough, as represented in fig. 1, at C. In square, this effect may be perpetually making the connection, it is to be observed, kept, while the acid in the cells is exs that the zinc surface of one trough must pended. correspond with the copper one of another, Though small plates have been recom. and the zinc of the latter with copper of a mended for medical purposes, we think large third, and so on. This arrangement may be ones will be found more likely to have a better conceived by placing them in the good effect. If the niedical advantage is to same order, and to end in such a way, that be derived from the stimulus of galvanism, all the zinc surfaces may face one way, and the effect of a perpetual and regular current the copper ones the other. After all the of that stimulus must certainly be pretroughs are connected together, let the two ferable to the rapid transmission of a small unconnected ends, at which the experi- quantity. ments are to be made, be as near together The galvanic shock may also be conveas possible.
niently given, by immersing the hands or A connection being now formed between the feet into vessels containing a solution of the two ends, one of which we shall term salt, and bringing wires from each end of the zinc end, and the other the copper end, the battery into the liquid. If any other the united energy of the whole will be part of the body is intended to be ope. transmitted through the connecting me. rated upon, a sponge, moistened with salt dium.
water, fastened to a metal plate connected
with one end of the battery, may be apEXPERIMENTS.
plied to the part, and the hand or foot pat The most striking and the most common into a vessel of the same liquid, connectexperiments are those which consist in the ed by a wire with the other end of the galvanic energy upon the organs of animals. battery. Small bits of sponge or bits of If two metallic rods, or, what is equally leather may be fastened to the end of the convenient, two silver spoons, be grasped, connecting wires, and made more or less one in each hand, the skin of the part be. moist as the delicacy of the part may reing previously moistened with a solution of quire. This contrivance is very useful in salt, and one of the spoons be brought in operating upon the eyes or ears. contact with one end of the battery, the When galvanism is used medically, it moment the other comes in contact with should first be applied very feebly, and the the other end of the battery, the shock is effect gradually increased, as the susceptiperceived. Fifty compound plates will give bility of the part will admit. If the part a shock which will be felt in the elbows. has, from disease, become so languid and in. One of a hundred will be felt in the shoul- susceptible, as not be sensible of the effect, ders. A greater number of plates give so it should be scarified, or by other means forcible a shock to the muscles, as to have the cuticle removed. This is somebe dreaded a second time. The shock ap- times the case with languid tumors, and pears to depend upon the number of plates. some cases of paralysis. Though we bad no The stun, or first impression, is much the great opinion of the medical agency of same, whatever may be the size of the galvanism, we have lately heard of several plates ; at least, from the size of two inches very successful cases, one of which in parti.
cnlar was the care of perfect loss of speech. the brass rods, H and K, are passed. It is If the naked metal of the wire, from a pow. plain, the two sides of this frame are insuerful battery, be applied to the skin, it be lated with respect to each other, at least comes cauterized and blistered.
as much as is necessary for any galvanic ex. If the plate, covered with a moistened periment. The part f, in fig. 4, being insponge, connected with one end of the bat- troduced into any of the holes, such as nm, tery, be applied to the back of the head, at the opposite end, F, is made to rest on the same time that the moistened fingers of the opposite brass rod, K. If the wires one hand are slightly applied to the other from the battery be now connected with end, a smarting sensation will be felt in the the frame at H and K, the gas will instantly part, and a taste at the same time will be begin to rise from the wires,,c and z, up infelt in the mouth, similar, but in a greater to the tube, while the liquid descends and degree, to that occasioned by the piece of occupies the cup. zine, and the shilling when laid upon the
A number of the apparatus, such as fig. 4, tongue. This experiment succeeds the may be employed at the same time; and if best with a small number of large plates, as
the different tubes are filled with different much as ten inches square.
liquids, such as the various solutions of salts,
and the communication of each occasionally Decomposition of Water and other Bodies. cut off, by placing some non-conductor at
E, their relative conducting powers may be The most simple way of performing this ascertained. experiment, is to bring the wires coming If two tubes of smaller size be placed, from each end of the battery into a vessel of one over the wire, z, and the other over water. A profusion of bubbles of gas will that of c, the gases may be collected sepaappear to be given out from each wire, as rately. far as they are immersed in the liquid. The If the tube contains a metallic solution, nearer the wires are brought together, so as such as silver, lead, or copper, the wire not to touch, the more rapidly the decom- from the copper end of the battery will afposition goes on. The gas produced from ford no gas; but the metal of the solution the wire coming from the zinc end of the will be reduced. Let the glass vessel A, battery, if the wire be of gold or platina, fig. 6, bave the two tubes, z and c, ground is found to be oxygen gas; but if the wire into its two necks. At the ends, z and c, be of any more oxydable metal, no gas will of the tubes, are tied bits of bladder, so appear, but the wire becomes oxydated. that any liquid in the tubes may have no The gas furnished by the wire from the tendency to enter the vessel A. The ves. copper end of the battery, of whatever kind sel being previously filled with some liquid, of metal the wire may be, is pure hydrogen. the tubes are so inserted that no air may If the immersed part of this, however, be exist between the ends of the tubes; the previously oxydated, no gas will be ob- tubes are also provided with two small served for some time, the hydrogen being caps of ivory or wood, through which the employed in reducing the oxide upon the platina wires, PP, are passed, reaching the surface.
bottom so near as not to pierce the bladBoth the gases are furnished from the ders. The tubes being filled with water, decomposition of the water.
and the wire from the zinc-end of the batAn apparatus more convenient for this tery connected with the wire of tube z, experiment, and at the same time fitted for while that of the copper is attached to that collecting the gases, is shewn in fig. 4; cg, of tube c, the decomposition of water will is a cup of glass capable of receiving the speedily commence, the wire in z affording glass tube, h; E c, and fz, are two wires of oxygen gas, while that of c affords hydrogen platina, fitted into two boles perforated in gas. In a very short time, the liquid of the the bottom of the glass cup; the tube, h, tube, z, will be found to contain muriatic which is close at the top, is first filled with acid; or rather, the oxy-muriatic; and the the water or other liquid, and the cup in- tube, c, will at the same time be found to verted upon it; the whole are then suddenly contain a fixed alkali. If the tubes be fill. returned into their erect position: this ap- ed with infusion of cabbage, the signs of paratus is then placed in the frame, fig. 5; alkali and acid are very soon observed, A B C D are four pieces of brass, united to. from the liquid of z becoming red, and that gether by the pieces of glass, Fand G, and of c green. If the connection be reversed, supported by four legs, through which also the liquids repass to the blue colour, and if