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the decomposition under naphtha : the moist iron tube projecting out on one side, and the potassa being placed between two plates of pla- vacant part of the gun-barrel, with its attached tina in a proper vessel, which is to be filled with tube of safety, charged with clean oil, or naphthia naphtha as soon as the contact with the battery on the other. A strong heat is then to be raised is established; in this way the action of the air in the furnace, and, when the iron turnings have is prevented, but the naphtha decomposes, and attained an intense white heat, a small furnace hydrogen and charcoal are liberated, which ren is to be applied to the tube containing the ders the result less satisfactory than in the more potassa, which, being readily fused, will flow simple form of the experiment. The most es- through the small hole at the bottom of the sential precautions are to preserve the alkali as tube upon the iron turnings. dry as is consistent with a sufficient degree of con- of the potassa combines with the heated iron, ducting power, and to employ the battery in a and the potassium condenses in brilliant laminae moderate state of action, in which it does not in the vacant part of the gun-barrel, which must produce a very intense heat, for that would des- be kept cool by ice during the process. As troy the metallic base at the moment of its pro- potassa always contains water, that is also deduction.
composed, and hydrogen escapes during the ex158. The amalgam of potassium, or sodium, periment, from the tube of safety; the cessation with mercury, is easily procured ; and may be ob- of this liberation of gas is the sign for removing tained by a very moderate power. A glass tube, the small furnace from the tube, and the heat one-fourth of an inch diameter and three inches being raised in the blast furnace for a few milong, having a short platina wire sealed in one end, nutes, as high as possible, to expel the last is to have mercury poured into it until the end portions of potassium from the iron, the whole the platina wire is covered; the rest of the tube is apparatus is suffered to cool. The gun-barrel is to be filled with a concentrated solution of alkali, then to be cut at the commencement of the part either pure or carbonated. The platina wire, which has been kept cool, for there the greatest surrounded by mercury, is then to be connected portion of potassium is usually found; it must with the negative end of a Voltaic battery, and be detached by a chisel in as large pieces as the circuit completed by bringing a platina wire possible, and introduced quickly into naphtha, a from the positive end, in contact with the solu- portion of which fluid it is expedient to pour tion of alkali. Gas will be evolved from this into the barrel as soon as it is first opened. wire, and the surface of the mercury will be 161. This process is attended with some difgreatly agitated; when the action grows weaker, ficulty, but it has been repeated successfully by the mercury may be poured into a glass of many chemists in this country : a more detailed water, and the presence of the alkaline metal account of it may be consulted in the thirtywill be immediately indicated by the evolution second volume of the Philosophical Magazine, of a cloud of minute bubbles of hydrogen gas, pp. 89, and 276. which may be collected by inverting over the 162. The composition of the fixed alkalies was mercury a small closed glass tube filled with entirely unknown before these experiments, but water. This result has been frequently obtained the volatile alkali, or ammonia, had been shown with a battery of thirty pairs of plates of only to consist of hydrogen and nitrogen, in the protwo inches square.
portion of three of hydrogen to one of nitrogen 159. The amalgam may be obtained more highly by volume. Now it is singular, that of three charged with the alkaline metal by employing a bodies, whose properties are so analogous, two solid piece of alkali, with a small cavity on its should be metallic oxides, and a third a comsurface, in which a globule of mercury is to be pound of two gases ; but there are experiments placed. The alkali is to be connected with the that seem to prove that either one or both of zinc surface of a battery, and the mercury with these gases contain a metallic substance, and that the copper surface; the mercury soon becomes consequently ammonia may be, like the other more tenacious, and sometimes is converted alkalies, a metallic oxide. into a soft solid mass, and in this state, if 163. Messrs. Berzelius and Pontin of Stockthrown into water, it produces a rapid decom- holm, discovered that when mercury is placed position.
in a Voltaic circuit with a solution of ammonia, 160. The strong attraction of the metals of the the mercury being connected with the copperalkalies for oxygen, renders them most active extremity of the battery, and the ammonia with agents of chemical decomposition ; by the the zinc, the mercury gradually expands to four strongest Voltaic power they can only be ob or five times its original volume, and becomes a tained in small quantity; and for the purpose of soft solid, nearly of the consistence of butter, experiment they are now usually procured by having its metallic character quite unimpaired. another process first devised by the French It is very remarkable, that by this change it chemists. A gun-barrel is bent nearly in the gains only about nados part of its weight; form of the letter S. An iron tube of the yet has its specific gravity so much dimincapacity of two cubic inches, having a small ished, that, from being thirteen or fourteen hole at the lower extremity and an iron stopper times heavier than water, it becomes only three at the top, is ground into one end of the gun- times heavier. By a short exposure to the atbarrel, and a tube of safety is fitted to the other. mosphere, it regains its original size and fluidity, The iron tube is to be filled with pure dry potassa, absorbing oxygen and reproducing ammonia. and the bent part of the gun-barrel nearest to it, When thrown into water a similar effect is prowith clean iron turnings: this part of the barrel is to duced, the water being decomposed and hydrobe luted and placed in a small blast furnace ; the gen liberated.
164. These phenomena are very analogous to to be the bases, as follows : namely, toat from those observed with the fixed alkalies; some sub- barytes, barium; strontites, strontium; lime, stance combines with the quicksilver and alters calcium; magnesia, magnesium ; alumine, aluits properties materially, without imparing its minum; silex, silicum, &c. metallic character ; now, according to all ex 170. The decomposition of the alkalies and isting analogies, this substance must he a metal, earths which had previously resisted every and this metal, in returning to the state of alkali, attempt at analysis, are a monument of the absorbs oxygen, as is seen by its action on water. importance of the Voltaic apparatus as an inHence it appears that ammonia consists of strument of chemical research ; and a proof of oxygen and a peculiar metal which may be the ability with which it has been employed, calied ammonium; but its analysis by other which will be regarded with admiration and apmeans evinces only the two gases, hydrogen and plause as long as science shall continue to be nitrogen; the former of these being the lightest cultivated. of all gravitating bodies, is most probably a 171. The phenomena that have been described simple or elementary substance; and, on such a as the consequences of Voltaic decomposition view, it would seem that nitrogen, though a obtain in every variety of experiment. Sulgaseous body, is a compound of oxygen and a phuric acid introduced into the Voltaic circuit metal.
gives off oxygen gas, and sulphur is deposited. 165. The amalgam of ammonium may be Phosphoric acid evolves oxygen gas, and phosformed most readily by making a cavity in a phorus combines with the negative wire. "Ammoistened piece of muriate, or carbonate of am- monia separates into hydrogen and nitrogen monia, connected with the positive side of a with a small proportion of oxygen. Oils, alVoltaic battery, and inserting in it a globule of cohol, and ether, when acted on by a powerful mercury connected by a platina wire with the battery, deposit charcoal, and give off hydrogen, Dezative surface; in a few minutes a soft amal or carborated hydrogen. 'And professor Brande cam is formed; it must be transferred into water has shown, that when animal Huids containing as quickly as possible when its action on that albumen, are placed in the Voltaic circuit, the fuid is to be observed, as it changes by the albumen is separated in combination with alkali shortest possible contact of the air.
at the negative wire, and in combination with 166. Sir H. Davy has observed, that the strong acid at the positive wire; and that, with a attraction of potassium for oxygen, enables it to powerful battery, it separates at the negative decompose ammonia even more rapidly than wire in the solid form; and with a less power, the Voltaic battery; and if an amalgam of potas- in the fluid form, so that it is probable animal sium and mercury be placed in a cavity in mois.. secretion may depend on some such power. tened muriate of ammonia, it immediately Prior to an examination of the Voltaic apincreases in size, and becomes more consistent. paratus there are some simple experiments that
167. As some of the substances called earths should be noticed. resemble the alkalies in various properties, it was 172. If a wire of silver, and another of zinc, conjectared, that they also were metallic oxides; be immersed in a glass containing dilute muriatic and this conjecture has been partly verified by acid, so as to remain at a little distance from the experiments of Messrs. Pontin and Berzelius, each other, the zinc will give off hydrogen gas and Sir H. Davy. If a paste be formed with rapidly, but the silver will produce no effect. water, and either barytes, strontites, lime, or Bring the ends of the wires that are out of the magnesia ; and this paste be connected with the acid in contact, by twisting them together; the positive side of a Voltaic battery, and touched quantity of hydrogen given off by the zinc will with an iron wire proceeding from the negative be diminished, and bubbles will be evolved surface, the wire obtains the property of decom- from the silver. posing water.
173. If zinc, iron, or copper, are employed 168. If a globule of mercury be placed in a in the same way with gold, in dilute nitric acid, carity in the earthy body, and touched with a similar phenomena ensue, but the gas produced wire proceeding from the copper end of the is nitrous gas. battery (the paste being connected with the zinc), 174. If a wire of iron and another of silver an amalgam will be soon formed, which has the are immersed in a solution of copper, the iron property of decomposing water, and forming will soon become coated with copper, but the with it a solution of the earth employed. If silver will remain unchanged. Bring the wires this amalgam be introduced into a little tube in contact, by twisting their upper extremities made of glass, and bent in the form of a together, and the silver will be soon covered with retort, then filled with the vapor of naphtha and
a coat of copper. hermetically sealed; on the application of heat 175. Similar experiments may be made with to the end of the tube containing the amalgam, a zinc and a silver wire, in solutions of lead or the mercury will distil over and leave the pure tin. metal of the earth behind. This process is rather 176. Dr. Wollaston, to whom we are indifficult, and requires great care.
debted for the last two experiments, thus ac169. The amalgam from barytes, strontites, counts for the result :—We know that when and lime, may be obtained with a battery of from water is placed in the circuit of conductors of 100 to 200 four-inch plates, in a moderate time; electricity, between the two extremities of a that from magnesia requires a longer continuance pile, if the power is sufficient to oxidate one of of the action of the battery, and the other earths the wires of communication, the wire connected do not readily yield to its powers. These metals with the opposite extremity affords hydrogen are named from the earths of which they appear gas.
177. “Since the extrication of hydrogen in connected. Whilst the compound arc remains, this instance is seen to depend on electricity, connect the two glasses by a second arc, formed it is probable, that in other instances, electricity of a piece of bent. wire of any kind, except may be also requisite for its conversion into gas. gold or platina. The silver will be immediately It would appear, therefore, that in the solution covered with a coating of copper, and will of a metal, electricity is evolved during the action continue to separate copper from the solution as of the acid upon it; and that the formation of long as the disposition of the apparatus remains hydrogen gas, even in that case, depends on a
Now the only difference in the transition of electricity between the fluid and arrangement, that appears to have operated as a the metal.
condition to the chemical power of the silver, 178. “We see moreover, in a former ex was the provision of another conducting comperiment, that the zinc, without contact of any munication between the glasses, in addition to other metal, has the power of decomposing that established by the compound arc; it therewater; and we can have no reason to suppose fore appears, that the associated metals cannot that the contact of the silver produces any new serve as conductors to the effect produced ; and power, but that it serves merely as a conductor indeed, if they did, it would be scarcely posof electricity, and thereby occasions the formation sible any accumulation of power could result of hydrogen gas.
from the increased number of plates in a Voltaic 179. 'In the last experiment, also, the iron by battery. itself has the power of precipitating copper, by 183. This experiment does not display any of means of electricity evolved during its solution; the electric powers of a Voltaic combination; and here likewise the silver, by conducting that but it shows that the association of three difelectricity, acquires the power of precipitating ferent substances is essential to the chemical the copper in its metallic state.'
agency of such a combination; and the pheno180. The experiments of this ingenious phi- mena will be found to correspond with some losopher, by which the attraction of alkali, and experiments of M. De Luc, on the efficient the precipitation of copper on the surface of groups in the Voltaic pile. This celebrated phisilver, were produced by the influence of negative losopher found that no chemical effects were electricity, excited by the ordinary machine, produced by any Voltaic arrangements, unless were considered by him as favoring the preced- two metals were employed with a liquid between ing explanation, and proving that oxidation must them; and, in the experiment last described, be the primary cause of electric phenomena. zinc, silver, and a metallic solution were inacTo Mr. Singer, who furnishes the quotation, tive, though in contact with each other, until the they did not appear to favor any such supposi- fluid was made the medium of conducting comtion, but rather the contrary; for in the experi- munication between the free extremities of the ment with two different wires, touching each combined metals. other, both produced the same chemical effects, 184. The experiment last described will sucyet, observes Mr. S., “if they are electrical at all, ceed, when the two glasses containing the me. the one is positive and the other negative, as all tallic solution, are connected by any moistened experiments on the association of different metals conductor; but the chemical power of the silver prove; and if two wires that have no chemical wire will be evinced slower, in proportion as the action on the fluid in which they are immersed, length of the moistened conductor is increased ; be rendered respectively positive and negative, and in all experiments of the kind, the less the they are well known to produce different chemi- interval between the extremities of the comcal effects.'
pound arc, the more rapid is its action on the 181. But it is said the chemical effect pro- interposed fluid. Hence, in the arrangements duced by the silver wire, arises from electricity of Voltaic apparatus, for the purpose of checommunicated to it by the zinc; and that we mical decomposition, the ends of the conducting have no reason to suppose that any new power wires are placed at a greater or less distance from is produced by the contact of the metals. Now, each other, in proportion as their action is reif this were the case, the mere conducting com- quired to be more or less intense. munication of the metals would be the only 185. The arrangement of a simple Voltaic condition necessary to give the silver its chemni- combination, by Mr. Sylvester, in which this cal power; but the case is widely different, the effect is apparent, may be referred to. It concommunication must be not only conducting, sists of a tall glass jar filled with very dilute but metallic, and even then no chemical effect muriatic acid. Through a cork, placed in the will be produced, unless the extremities of the neck of this jar, two wires are inserted; the one wires are immersed in the same liquid, or in a short straight wire of zinc, the other a long two separate portions of liquid that have a con bent wire of platina, or silver; by turning this ducting communication with each other. last round, its upper end may be brought in
182. Place two glasses filled with a solution contact with the zinc, or separated from it at of copper near each other. Make a compound pleasure. When they are separate, the zine arc, by twisting together the end of a wire of only is acted on; but, as soon as they are brought zinc, with the end of a similar wire of silver. in contact, the platina or silver becomes covered Connect the two glasses by placing the silver with bubbles of gas, which appear soonest, and leg of the arc in one, and the zinc in the other. are evolved in the greatest quantity, from the The zinc will immediately attract copper from projecting point. the solution, but it does not communicate that 186. Notwithstanding this circumstance, the power to the silver, though they are both closely power of a simple Voltaic combination con
tinues to exert its effect, when the stratum of with the metallic solution is not absolutely neinterposed fluid is considerable. If a tube of cessary to the success of these experiments; it three feet long be filled with dilute muriatic acid, is only essential that a regular Voltaic circle, and a wire of platina be inserted through a cork consisting of two different metals and a moist in one of its extremities, and a wire of zinc in conductor be established. the other, on connecting the wires, gas will be 190. If we take a glass tube having a piece of soon evolved from the silver. If the tube be bladder tied over its lower extremity water tight, bent the effect will take place more slowly. Mr. and a cork inserted in its upper end with a plaSinger took two similar tubes of eighteen inches tina wire passing through it; and the tube be long, and connected them by a short piece of filled with acetate of lead, and placed in a small texible pipe, so as to form together a tube of three cup of zinc containing dilute muriatic acid; we feet in length, with a joint in the middle, which shall find that, when a metallic communication is admitted of its employment either as a straight formed between this cup and the platina wire, tube, or as a siphon with a bend of any required the latter will become studded with brilliant inclination. In the open ends of this tube he crystals of metallic lead. In this case the oxiplaced respectively a zinc, and a platina wire; dable metal has no connexion with the metallic and found that, whenever their outer ends were solution but through the medium of the platina connected by a wire, hydrogen was soon evolved wire on the one side and moist bladder on the from the platina ; but this effect took place other. soonest when the tube was straight, and hence 191. Fill two similar glasses, the one with a it appears that the power put in motion by these solution of silver, the other with dilute muriatic combinations, can pass more readily through any acid; connect them by a compound wire arc given column of a fluid in a straight line, than of zinc and platina; the zinc being plunged in in any other direction.
the muriatic acid, and the platina in the metallic 187. It has been seen, that, when any metal is solution. Immerse a second arc, formed of a in solution in the interposed Auid, it is revived bent silver wire, in the two glasses, one of its by the wire which in other cases evolves hy- legs being in each; after some time the zinc wire drogen; and it has been shown, by the effect will be entirely dissolved, and the platina will of the silver and the platina wire, that metals be found covered with minute crystals of metallic which have no chemical action on the interposed silver, displaying a very beautiful appearance fluid alone, may decompose it when combined under the microscope. with another metal. These facts, though far 192. Copper and zinc are the metals most from being perfectly understood, may serve to usually employed in the construction of Voltaic explain some chemical effects which were before apparatus, for their effects are greater, in proporrather obscure. If a zinc wire, for instance, be tion to the value of the metals, than those of immersed in a solution of lead, the latter metal any other combination. Silver and zinc, or gold will be revived in the form of a metallic vegeta- and zinc, would be more powerful, but not so tion, which increases gradually by additions to much so as to compensate for the increased exits extremities. The first separation of the lead pense. · is sufficiently intelligible; the acid in which that 193. As the effects produced by a single pair metal is dissolved, having a stronger attraction of metals, of any size, are still exceedingly feeble, for the zinc, dissolves a portion of it, and de- attempts were made to combine the action of posits on its surface an equal portion of lead. several pairs. Professor Robinson arranged a But the lead, so revived, continues to revive series of zinc and silver plates, about the size of more, and to receive additions at its remote ex a shilling, so as to form a rouleau; and on aptremities, whilst it would have been rather ex- plying his tongue to the edge of this, the sensapected these additions would have been made on tion experienced was more manifest than by a the zinc, and the vegetation that had been first simple pair of metals; but its power in other formed protruded further into the fluid by that respects did not appear more considerable. In means. The contrary result is now understood to this arrangement every zinc plate was necessarily be obtained, by the revived particles of lead between two silver plates, and every silver plate forming a Voltaic combination with the zinc and between two of zinc, with the exception of the the surrounding Auid. This effect is analogous to first and last. Now it has been stated, that the that which obtains in various other instances. contact of zinc with silver, or copper, occasions
188. Spread a few drops of a solution of silver some electric fluid to flow from either of those upon a pane of glass, and place a small piece of metals to it; and, consequently, when a single platina, and a similar piece of copper wire upon pair of metals are associated, the outer surface ii, at a little distance from each other. A vege- of the zinc appears positive, and that of the tation will take place about the copper wire; silver or copper negative.
But if both surfaces but no effect will be produced by the platina. of the zinc are in contact with copper or silver, Bring the wires in contact with each other, and electricity will flow into it in contrary directions, the Voltaic combination thus formed will occa so that neither surface can exhibit the effect; and sign a beautiful vegetation of metallic silver to the same circumstance occurs, in a contrary surround the platina wire.
order, when both surfaces of a silver or copper 189. With a solution of tin, and wires of zinc plate are in contact with zinc. Hence every and platina, similar phenomena occar; but a arrangement of this kind, however numerous the considerable time elapses, after the contact, pairs of metal, will exhibit at its opposite before the vegetation appears round the platina. extremities the powers of a single pair of metals The immediate contact of the oxidable metal only.
194. Volta had the penetration to ascertain the quired considerably less time to keep it in proper cause of this defect in the rouleau of professor order. This form of the apparatus, which is Robison; and his ingenuity supplied a means called the Voltaic trough, or battery, has been of obviating it. His experiments on the combi- much used in this country; it is perhaps, on the nation of two metals with an imperfect conductor whole the best arrangement hitherto devised, and (as water or saline fluids) had taught him that its construction is sufficiently simple. the electro-motive power of these Auids inter 198. The zinc plates are made by casting that fered but little with the more powerful energy of metal in an iron or brass mould; they may be the combined metals; and that in fact they about an eighth of an inch thick. The copper acted principally as conductors to that erergy. need not exceed twelve or fourteen ounces to He therefore interposed imperfect conductors of the square foot, and may be soldered to the zinc this kind between a series of pairs of metal, at one edge only, the other three being secured and thus combined their power without pro- by cement in the trough. ducing a counteracting current ;. for the zinc and 199. The trough must have as many grooves silver, or zinc and copper, were then in contact in its sides as the number of plates it is intended with each other at one surface only, but the con to contain, which should be fewer in proportion ducting communication existed throughout. to their size, otherwise the apparatus will be in
195. To construct an apparatus of this kind, convenient from its weight. When the plates procure a number of plates of zinc and copper, are not more than three inches square their or zinc and silver, either round or square, of any number in one trough may be fifty, and the dissize; and an equal number of pieces of cloth, tance of the grooves from three-eighths to half leather, or pasteboard, of the same form, but an inch, The trough must be made of very dry rather smaller. Soak these last in salt water, wood, and put together with white lead or until they are thoroughly moistened; place a cement. The plates being placed to the fire, plate of silver, or copper, upon the table, then the trough is to be well warmed, and placed houpon that place a piece of zinc, and on the zinc rizontally on a level table, with its bottom downone of the moistened discs; upon this a second wards, very hot cement is then to be poured into series of silver, zinc, and moistened cloth (or it, until the bottom is covered to the depth of a pasteboard) in the same order; and thus conse- quarter of an inch. During this process the cutively until a series of fifty or sixty repetitions plates will have become warm, and they are have been placed one upon the other. Particular then to be quickly slided into the grooves and care must be taken to place the plates in regular pushed firmly to the bottom, so as to bed themorder; if in the first group silver is placed selves securely in the cement. In this way the lowest, zinc next, and then the moistened disc, plates are very perfectly cemented at the bottom, the same disposition must be observed through- and, when this cement is sufficiently cool, a slip
of thin deal is to be slightly nailed on the top 196. The Voltaic pile being thus formed, let edge of one of the sides of the trough, so as to the operator moisten both his hands with brine, overhang the inner surface about a quarter of an and grasp a silver spoon in each. If the top of inch. The trough being about three quarters of the pile be then touched with one spoon, and an inch deeper than the diameter of the plates, the bottom with the other, a distant but slight there will be an interval between their top edges shock will be felt at every repetition of the con- and the deal slip; and, when the side of the
This shock resembles very nearly the trough to which the slip is attached is laid fat sensation produced by a very large electrical upon the table, this interval forms a channel into battery weakly charged; it is greater in propor- which very hot cement is to be poured, and it tion to the number of groups of which the pile will flow between each pair of plates, so as to is composed. If the communication is made cement one side of all the cells perfectly. As with any part of the face near the eyes, or with soon as the channel is quite full of fluid cement, a silver spoon held in the mouth, a vivid flash the strip of deal is to be torn off, and the trough of light is perceived at the moment of contact, inclined so as to admit the superfluous cement to and that whether the eyes be open or shut.
When this is effected, and the cement 197. The power of an apparatus of this kind cool, a slip of deal is to be nailed on the oppocontinues for some time, but gradually diminishes, site side and the same process pursued with that. the zinc surfaces becoming oxidated by the ac- The instrument will then be cemented in the most tion of the moisture; it therefore requires to be perfect manner, and it may be cleaned off and taken to pieces and cleaned, an ration that is varnished. very troublesome when the number of plates is 200. We may notice the preparation of elecconsiderable. This inconvenience was dimi- trical cements. The various cements employed nished by soldering each pair of zinc and copper in the construction of electrical apparatus are plates together, instead of simply laying them formed principally of resin, with the addition of on each other; and a further improvement was some substances to render it more adhesive, and devised by Mr. Cruickshanks, which consisted in less brittle. Five pounds of resin, one pound of cementing the pairs of plates in regular order, in bees'-wax, one pound of red ochre, and two table grooves made in the side of a mahogany trough, spoonfuls of plaster of Paris, when melted, and so as to form water-tight cells between each pair. well incorporated together, form a very good These cells being filled with water, or any con cement for general purposes.
One that is well ducting fluid, served as a substitute for the mois- adapted for cementing large Voltaic batteries, tened discs used in the pile; and, as fluid and which is cheaper, may be formed of six could be easily poured out and replaced, it re- pounds of resin, one pound of red ochre, half 2