4. Batteries consisting of one Metal and two or three Liquids. If a number of U-tubes (App. 5) be filled on one side with concentrated, on the other with dilute sulphuric or nitric acid, and connected by arcs of the same metal dipping into the liquids-e. g., tin, lead, iron, copper, or silver-an efficient battery is obtained. With sulphuric acid and iron, positive electricity goes from the end of the arc which dips into the dilute acid to that which dips into the strong acid; the contrary with tin and sulphuric acid. (Faraday, p. 400.) If one end of the copper arc be immersed in solution of liver of sulphur, the other in dilute sulphuric acid, the solution of liver of sulphur being connected with the acid by a film of solution of common salt, a powerful battery is produced. (H. Davy.) In a pile consisting of the following elements-cloth saturated with water, plate of metal (lead, copper, or silver plates answer best), cloth soaked in solution of liver of sulphur, cloth soaked in water, plate of metal, &c.-positive electricity goes through the metallic arc from the last element to the first. (H. Davy.) 5. Grove's Gas Battery. This battery consists of a series of tubes, containing strips of platinum foil covered with a pulverulent deposit of the same metal. The tubes are arranged in pairs in separate vessels of dilute sulphuric acid; and of each pair, one tube is charged with oxygen and the other with hydrogen gas, in quantities such as to allow the platinum to project above the dilute acid into the atmosphere of gas in the upper part of the tube. The platinum in the oxygen of one pair is metallically connected with the platinum in the hydrogen of the next; and thus a series may be composed of any number of pairs.-A battery of four cells constructed in this manner will decompose acidulated water; a single cell will decompose iodide of potassium; and twenty pairs will produce very powerful effects, such as giving a shock which may be felt by several persons at once, producing a brilliant light between charcoal points, &c. When the poles are unconnected, a gold-leaf electroscope connected with either of them is sensibly deflected. When distilled water is substituted for acidulated water in the cells of the battery, the effects are similar but more feeble. The current of positive electricity proceeds, within the battery, from the hydrogen tube to the oxygen tube in the same pair,—so that in the voltameter, the platinum connected with the terminal oxygen tube of the battery becomes the positive pole or anode (vid. Electrolysis, p. 431). In fact, the hydrogen in the battery tubes is the oxidable body, acting like the zinc in the ordinary battery. Both gases in the battery tubes are absorbed,—but the hydrogen twice as fast as the oxygen. It is essential that the platinum plates be immersed in the gases as well as in the liquid: for when these plates are made so short as not to project above the liquid, no action takes place. The use of the finely divided platinum is, of course, to increase the surface of contact. The rationale of the action appears to be as follows: "When the circuit is completed-at each point of contact of oxygen, water, and platinum, a molecule of hydrogen leaves its associated molecule of oxygen to unite with a molecule of the free gas; the oxygen thus thrown off unites with the hydrogen of the adjoining molecule of water; and so on,-till the last molecule of oxygen unites with a molecule of free hydrogen:--or we may conversely assume that the action commences in the hydrogen tube." Mr. Grove likewise tried various other combinations of gases, viz. chlorine and hydrogen, chlorine and carbonic oxide, oxygen and nitrous oxide, oxygen and nitric oxide, hydrogen and carbonic oxide, &c.; but none of them were found to be adapted for actual use in the battery. Chlorine and hydrogen gave a powerful current; but the rapid absorption of the chlorine soon put a stop to the action. Chlorine and oxygen, on the one side, and hydrogen and carbonic oxide, on the other, were the only gases which appeared to be decidedly capable of combining electrosynthetically, so as to produce a voltaic current. The other combinations produced no effect, excepting for the first few minutes. Olefiant gas should perhaps be excepted: it appears to give a continuous but feeble current. The vapours of bromine and iodine, were they less soluble, would probably also be found efficient as electro-negative gases. (Phil. Mag. J. 21, 417; 24, 268, 346 and 422.) T I. Electricity developed by the Vital Process. Certain fishes, as Torpedo unimaculata, marmorata, Galvanii (the Electric Eel), and Narke (the Electric Ray); Silurus electricus; Tetraodon electricus, and Gymnotus electricus, have the power of constantly generating the two electricities in their bodies, in large quantity and of considerable tension, and imparting electric shocks. In the Electric Ray, negative electricity proceeds from the under, positive electricity from the upper surface of the body. The electricity, when conducted away by wires, acts upon the magnetic needle, and decomposes liquids. (J. Davy.) Sparks may also be obtained from the Electric Ray by means of a peculiar apparatus. (Linari & Matteucci.) Comp. Humboldt (Ann. Chim. Phys. 11, 415); J. Davy (Phil. Trans. 1829, 15; also Schw. 57, 17; also Pogg. 16, 311;--Phil. Trans. 1832, 259; also Pogg. 27, 542); Linari & Matteucci (Pogg. 38, 292); Matteucci (Pogg. 39, 485); Linari (Pogg. 40, 642); Colladon (Pogg. 39, 411). Faraday has examined the electric force of the Gymnotus. He finds that the shock is strongest when one band is applied to the head and the other to the tail,--and diminishes in force as the points of contact are brought closer together. The galvanometer was affected, and iodide of potassium decomposed---in such a manner as to show that the current proceeds from the anterior towards the posterior part of the fish. The spark was also obtained by means of a magneto-electric coil. When the shock was strong, it was like that of a large Leyden battery charged to a low degree, or that of a voltaic battery of perhaps one hundred and forty or more pairs, of which the circuit is completed for a minute only. (Phil. Trans. 1839, I, 1; Phil. Mag. J. 14, 211.) The spark had previously been obtained from a gymnotus by Fahlberg and Guisan. (De Gymnoto electrico, Tubingen, 1819.) T. II. INFLUENCE OF ELECTRICITY ON THE CHEMICAL NATURE of 1. Combinations brought about by Electrical Influence. The combination of the two electricities often causes combustible bodies, which may be present at the place of combination, to unite with oxygen, chlorine, &c. To this class of effects belong the inflammation of a mixture of oxygen with hydrogen or other combustible gases, or of chlorine with hydrogen, by the simple electric spark; of alcohol, ether, colophony, and gunpowder by slight electric discharges or by the simple spark; the burning of various metals in the form of thin wire or foil, when the combination of the two electricities takes place within their substance, and of charcoal by strong electric shocks or by the galvanic battery; and the combination of nitrogen with oxygen, when electric sparks are made to pass for a long time through a mixture of those two gases. According to Faraday, large electric sparks passed over litmus paper produce nitric acid sufficient to redden it. In most of these cases, electricity appears to act by the development of heat which accompanies the union of its two kinds: it must, however, act in a different manner in the combination of oxygen and nitrogen, since this combination is not effected by heat. In this case, as in the inflammation of hydrogen by a small electric spark, the compression which the gases sustain in the passage of the spark must also be taken into account. 2. Decompositions produced by the action of Electricity. When the two electricities are made to enter a compound body, either solid, liquid, or gaseous, which is not a perfect conductor, the compound îs frequently resolved into its elements. A. Decompositions produced by repeated Electric Discharges. When the combining electricities are endued with high intensity, and their union takes place in the form of a succession of sparks in a compound gas or a compound solid body, decomposition of the compound often takes place. This effect may in some cases be due to the high temperature produced by the electric discharge, since many of these decompositions may also be produced by heat; but this is not always the case. Repeated discharges from the common electrical battery decompose oxide of mercury into mercury and oxygen gas. Bonnijol decomposed chloride of silver, and even hydrate of potash enclosed in glass tubes, by repeated electric sparks; the silver separated in ten minutes; the potassium burnt immediately after separation. Continued discharges from the common battery, or even simple electric sparks, partially decompose carbonic acid gas into oxygen and carbonic oxide, olefiant gas and light carburetted hydrogen into carbon and hydrogen gas,-likewise phosphuretted hydrogen, sulphuretted hydrogen, hydriodic acid, hydrochloric acid, and ammoniacal gases, into phosphorus, sulphur, iodine, chlorine, and nitrogen, on the one hand, and hydrogen on the other. B. Decompositions produced by the continuous Discharge of Electricity of small Tension. If the two electricities proceeding from the poles of a voltaic battery, or any other suitable source, be made to flow through two good conductors, not in contact with each other, into a compound liquid, the three following cases may arise. 1. The liquid conducts the electric current very well, and gives passage to it, without undergoing any alteration.-This is the case with solutions of various metals in mercury, and with fused alloys. 2. It completely stops the current, and suffers no decomposition: if, however, the electricity possesses great intensity, it may force a passage mechanically through the liquid. 3. The liquid allows more or less readily the continual ingress of the two electricities, but is at the same time decomposed; and only in so far as the decomposition goes on, is the passage of the current possible,--so that the (apparent) conducting power of the liquid is directly proportional to its decomposibility, or else identical with it.-To this class belong all liquids mentioned on page 311, under the head b, with the exception of fused protiodide of mercury, which conducts well without being decomposed. All gases act as non-conductors, and are not decomposible by electricity of small tension. Solid compounds likewise resist decomposition, in consequence of the immobility of their particles, excepting when they are in contact with liquids on which the electric current acts. In the decomposition of liquids of class 3, the elements are always liberated close to the conductors by which the two electricities are introduced, and, according to their different natures, are either evolved in gas-bubbles or deposited in the solid form, or dissolve in the undecomposed portion of the liquid surrounding the conductor, or combine chemically either with the conductor or with other elements of the liquid, thereby giving rise to Secondary Products. The two good conductors by which the two electricities are introduced into the liquid are the Polar Conductors, Polar Wires (they may, however, consist of charcoal, graphite, or mercury), or Faraday's Electrodes. The conductor which introduces the positive electricity is the Positive Polar Wire, Faraday's Anode, Smee's Oxode, Graham's Zincode or Zincoid. The conductor which introduces the negative electricity is the Negative Polar Conductor, Faraday's Cathode, Smee's Hydrogode, Graham's Platinode or Chloroid.--The liquid decomposed by the electric current is Faraday's Electrolyte, and the decomposition produced by electricity, Electrolysis.--The elements of the liquid evolved on the polar conductors are Faraday's Ions; the electro-negative elements evolved at the positive conductor or anode being called Anions, and the electropositive elements evolved at the negative conductor or cathode, Cations. The vessel in which the decomposition of the liquid takes place is called the Decomposing Cell. [Electrolytes must be regarded as non-conductors, which, though they may be broken through by electricity of high tension, will not allow electricity of low tension to pass quietly through them. In the latter case, therefore, the two electricities are unable to combine with one another; but they may unite with the elements of the liquid. It has been assumed (pp. 157 and 342) that hydrogen, when in the free state, contains negative electricity, and oxygen positive electricity combined with it,—and that when these two bodies unite, the two electricities combine together and form heat, which is partly set free, and partly perhaps remains combined with the water. Now when negative electricity acts on one part of the water, and positive electricity on another, the former unites with the hydrogen of the contiguous atom of water, the latter with the oxygen of another atom of water: hence hydrogen gas is evolved at the cathode, and oxygen at the anode. The electric fluids entering the liquid with a certain tension, and in a certain quantity, their affinity for oxygen and hydrogen overcomes the mutual attraction between those elements, somewhat in the same manner as the increased affinity of caloric for carbonie acid at a red heat decomposes carbonate of lime. Moreover, while an atom of hydrogen is evolved at the negative conductor, and an atom of oxygen at the positive, a transposition of atoms (as described at p. 343, ƒ) takes place throughout the row of atoms of water lying between these points; so that the liquid in the middle remains quiet, and no transference of matter from one electrode to the other can be detected. The greater, however, the distance between the points at which the electrodes dip into the liquid, and the greater, therefore, the number of atoms which must be transposed, the higher will be the electrical tension required to overcome this resistance. As with water, so also with all other electrolytes;—their cation, a metal for example, resumes the negative electricity which it had lost on combining with the anion, such as chlorine, bromine, iodine, &c.,-and this again resumes its positive electricity. In all these cases, the negative electricity which the cation takes up must correspond to the positive electricity taken up by the anion,-that is to say, the required quantities of electricity must be to one another in the proportion in which they combine to form heat. When the oxygen liberated at the anode is not evolved as gas but combines with the anode-e. g., when the latter consists of zinc-we may suppose that the negative electricity, as it is set free, combines with the positive electricity proceeding from the battery, and that in this case the decomposition is effected by the affinity of negative electricity for hydrogen and of zinc for oxygen. According to this view, electrolytes are not really conductors,-they do not permit the combination of the two electricities,-no electric current passes through them, but their elements continually take up the elective fluids as they enter, and thus give rise to a constant current in the electrodes. The apparent conducting power of electrolytes is greater therefore in proportion to the facility with which they are decomposed, that is, to the rapidity with which their elements take up the electric fluids proceeding from the battery, and separate from the liquid. We are at present unable to explain why pure water resists the transposition of its atoms with greater force than water combined with acids or salts.] [The theory here given of decomposition by the electric current is in the main the same as that of Grotthuss. (Ann. Chim. 58, 65; 63, 34.) That philosopher likewise supposed that, in the decomposition of water, positive electricity combines with the oxygen of the atom of water lying next to the positive wire, and negative electricity with the hydrogen of the atom of water next to the negative wire, and that between the two poles transposition of atoms takes place. The production of flame, which accompanies the combination of oxygen and hydrogen gas, was likewise attributed by Grotthuss to the combination of the positive electricity in the oxygen with the negative electricity in the hydrogen. The only difference between his theory and the preceding is that he supposes a linear transposition of atoms to take place (something like that represented in App. 23, instead of a semicircular up and down motion. Sir H. Davy (Gilb. 28, 39) and W. Henry (Ann. Phil. 1, 465) propounded |