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Likewise gold, magnetic iron ore, specular iron, red oxide of copper, and iron pyrites, become positive in water with peroxide of manganese or graphite. (Becquerel.) [With respect to peroxide of manganese, vid. p. 345, p.-Does the action of graphite result from its having absorbed oxygen from the air?] Platinum is positive towards peroxide of lead in pure water. (Schönbein.)

If platinum be laid on the condenser of the electrometer, damp paper on the platinum, peroxide of manganese on the paper, and the oxide of manganese touched with dry wood, the condenser will show positive electricity. When platinum and peroxide of manganese are connected with the galvanometer, positive electricity passes from the peroxide of manganese through the galvanometer to the platinum. In pure water, the current is very weak,--but stronger with irregularly crystallized peroxide of manganese than with large single crystals, because the former is more prone to decomposition. If the oxide of manganese be left for a considerable time in water by itself, and then connected with platinum in nitric acid, the current at first goes the contrary way—a proof that the oxide of manganese has been superficially altered by the water. (Dela Rive.)

If zinc with copper and water give an indication of 4° in the voltaic electrometer, it will give 4, with silver, 4, with charcoal, 5 with gold, 5. with black sulphuret of mercury, 6 with iron pyrites, 6 with peroxide of manganese, and 9d with peroxide of lead. (Rosenchöld.)

Electrical series of metals in water, beginning with the most highly electro-positive: Zinc, lead, tin, iron, antimony, bismuth, copper, silver, gold. (Fechner.)

Experiments with Dilute Acids, not including Nitric Acid.A solution of 1 part of potassium in 1000 parts of mercury is highly positive towards zinc.-Amalgam of zinc is positive towards zinc, and amalgam of tin towards tin. (H. Davy.)

Perfectly pure zinc dissolves more slowly in dilute sulphuric acid than commercial zinc, which contains 1 per cent. of iron, together with cadmium and traces of lead and tin-or than an alloy of 10 parts of zinc with 1 part of tin, lead, iron, or copper,—because these impurities give rise to local electro-chemical action (p. 344, i. 4). When commercial zinc and pure zinc are placed in dilute sulphuric acid of various degrees of strength (the annexed per centages show the quantities of anhydrous sulphurio acid in the liquid), the times required to furnish a given quantity of hydrogen gas are found to be as follows:

25.64 29.85

43.25 64.2 per cent. Commercial zinc ..

1.5

4.5 Pure zinc .....

55

13 12 45 Hence, commercial zino is most quickly dissolved by dilute sulphuric acid containing from 25 to 43 per cent. of real acid, -and pure zinc by that which contains from 30 to 43 per cent.

The evolution of gas is very slow at first, but gradually increases, reaching its maximum in 10 minutes with commercial zine, and after several hours with pure zinc: with acid of 64 per cent, however, the evolution of gas soon diminishes. [Does this arise from the formation of a film of sulphate of zinc?] De la Rive.

Alloys of 10 parts of zinc, with 1 part of tin, lead, iron, or copper, being immersed in dilute sulphuric acid of various degrees of strength, a comparison of the times required for the evolution of a given quantity of hydrogen gas, with the corresponding intervals in the case of pure and commercial zinc, gives the following results:

35.28

20.2

3 108

1.5

2

1 15

20.2 25.64 29.85 p.C.

20.2 25.64 29.85 E Pare zinc .... 207 110 30

Lead-zinc 12 9 10 Commercial zinc

3 2

Iron-zinc 1 3 2 Tin-zinc ...... 24 12 12

Copper-zinc .. 5 6 4 With copper-zinc the evolution of gas continually diminishes, because the alloy becomes covered with a black film of oxide of copper (metallic copper!); when this is removed, the evolution of gas again becomes rapid. - The solution of pure zinc is greatly accelerated by binding it round with platinum wire. (De la Rive.)

When four balls of zinc of equal size are immersed for an hour in equal quantities of dilute sulphuric acid, contained in four vessels of equal size, but different materials, the quantity of zinc dissolved in the glass vessel is found to be 1.5, in the silver vessel 51, in the gold vessel 65, and in the platinum vessel 79 millegrammes. On being afterwards immersed for an hour in four glass vessels containing equal quantities of acid of the same strength, the ball previously immersed in the other glass vessel loses 1:5, that from the silver vessel 5, from the gold 8, and from the platinum 11 millegrammes. (Bouchardat, Ann. Chim. Phys. 53, 284.) (Had the balls the same temperature in the second experiment?]

Balls of zinc immersed for the same time in dilute sulphuric acid, dilute hydrochloric acid, or solution of ammonia, lose, accordivg to Bouchardat, the following quantities, varying with the nature of the containing vessel.

Vessels. Glass Sulphur Black lead Tin... Lead Antimony Bismuth ..

Hyd. ac. Sulph. ac. Am.
4

3
5

3 1
10
12

12 12
14

28 15 41

38 18 45

20

Vessels,
Silver
Gold
Platinum,
Copper
Brass
Iron

Hyd. ac. Sulph. ac. Am. 58

65 22 52

100 24 55

116 27 70

150 40 124

190 103 130

With balls of commercial zinc, the loss of weight in dilute sulphuric acid in a quarter of an hour amounts, in glass vessels to 9, in sulphur to 10, in lead to 310, in antimony to 350, in bismuth to 342, in silver to 665, and in platinum to 712. (Bouchardat.)

Two zinc plates of equal size being placed in dilute sulphuric acid (1 part oil of vitriol with from 8 to 16 of water), and one of them connected with a plate of polished lead, the second loses much less weight than the first (this is contrary to Bouchardat's statement); with hydrochloric acid an opposite result is obtained. (Runge, Pogg. 43, 581.)

To obtain amalgamated zinc, mercury is placed upon the zinc, toge ther with dilute sulphuric acid, and both liquids spread upon the plate by means of a pad of cloth or linen, the acid being from time to time renewed. (Masson, Ann. Chim. Phys. 60, 334.) Or the bottom of a capacious dish being covered with mercury and sulphuric acid poured upon it, the zinc plate is immersed in the acid, its surface touching the mercury,-turned after two or three hours, and afterwards taken out. (Liebig, Ann. Pharm. 29, 111.) [This covering of the zinc with mercury depends on a peculiar galvanic action. The mercury,—which is in contact with the zinc at one point, and takes up the negative electricity set free in the zinc,-instead of giving rise to a transposition of atoms in the water, attaches itself, in consequence of its mobility, to the zinc, and thus imparts negative elec

tricity directly to the hydrogen-atom of the atom of water which has given up its oxygen to the zinc.]

Amalgamated zinc when alone is not attached by dilute sulphurio acid; but when it is connected with platinum or other metals, a powerful action takes place, the hydrogen gas being wholly evolved on the surface of the platinum, not upon the zinc. (Faraday.)-Amalgamated zinc immersed in dilute sulphuric acid becomes covered after a time with gasbubbles, which adhere strongly to it; no loss of weight can be detected in the zinc, even after four-and-twenty hours. The adhering hydrogen gas appears then to protect the zinc from the action of the liquid. When amalgamated zinc is connected with platinum, the hydrogen being all transferred to the platinum, the zinc is dissolved. If the dilute sulphuric acid contains a little nitric acid mixed with it, that acid converts the hydrogen into ammonia, aud then the amalgamated zinc dissolves, even though not connected with platinum. (Daniell, De la Rive.) [But pure zinc likewise becomes covered with bubbles, and dissolves revertheless.]— The coating of mercury makes the surface of the zinc uniform, so that the alloys possibly contained in it cannot give rise to any local electro-chemical action; it therefore makes commercial zinc like pure zinc. (Grove.) [But pure zinc dissolves, although the action goes on slowly,-amalgamated zinc not at all.] The mercury appears to prevent, in some unknown manner, the direct transference of negative electricity from the zinc to the hydrogen (p. 345, i, 5.)

Amalgamated zinc in dilute sulphuric acid is positive towards the same metal unamalgamated (H. Davy); because the latter, in consequence of the strong purely chemical action, is more quickly surrounded with saturated sulphuric acid (which, however, should be soonest removed by the rapid disengagement of gas). (Faraday.)

When two pieces of amalgamated zinc of the same size are immersed in dilute sulphuric acid, and one of them is connected with copper, the latter piece loses 32:31 parts for every 1 part of hydrogen evolved at the surface of the copper (1 at. H. to l'at. Zn.), while the other piece suffers no diminution. (Faraday.)

Amalgamated zinc produces with copper a much more copious current than ordinary zinc. (Poggendorff.)

An amalgamated zinc plate, connected with copper, and immersed in dilute sulphuric acid, loses more weight in the second half hour than in the first, in the third more than in the second, and so on, till it is again amalgamated. (Binks.)

Amalgamated zinc in dilute sulphuric acid, in connection with amalgamated copper which dips into mercury, or only with amalgamated platinum, is at first strongly positive,—but the current ceases in a few minutes: but on replacing the amalgamated zinc by unamalgamated platinum, a current in the contrary direction is set up. The amalgamated metal is positive. The mercnry probably combines with hydrogen, and thereby becomes as strongly positive as the amalgamated zinc. (Grove:)

Black lead or freshly ignited gas-coke placed in sulphuric acid with amalgamated zinc immediately liberates hydrogen gas; porous coke and box-wood charcoal, on the contrary, not till after some time, because they absorb the first portions of liberated hydrogen. If they are then placed by themselves in a solution of lead, copper, mercury, silver, or gold, they become covered with a thin metallic film, just as they liberate iodine from iodic acid. Coke retains hydrogen for forty-eight hours. (Smee.).

Zinc gives with iron in dilute sulphuric acid a current four times as abundant as with copper, the size of the plates being the same in bot cases,—so that a ten-pair battery of zinc and iron yields in seven minu' (if the polar wires are made to dip into water) as much detonating cras a battery of zinc and copper of the same dimensions. But.i-is only the quantity of the electric current that is greater in the case of zinc and iron; the tension is smaller. At the first moment of immersion, the quantity also is greater with zinc and copper; bnt the copper soon becomes covered with a dark film of oxide (sulphuret ?], while the iron remains clean,—and this film interferes with the electrical conduction between the copper and the liquid. When a pair of zinc and iron plates, and a pair of zinc and copper, are left in action for twelve hours, the following loss of metal is observed: Copper, 0; zinc connected with it, 96 grains; iron, 6 grains; zinc connected with it, 74 grains. It appears, then, that a small quantity of iron is dissolved; and of the zinc connected with copper more than of the other zinc,--and yet the quantity of the current is greater with zinc and iron. (Hence, zinc and copper produce a greater amount of purely chemical action]. (Martyn Roberts, Phil. Mag. J. 16, 142; 19, 106.)

Zinc' and iron produce a more copious current than even zinc and silver or zinc and platinum, both in dilute sulphuric and dilute nitric acid; and the plates of the zinc and platinum pair must have a surface three times as great as that of the zinc and iron to yield the same quantity of electricity. But the intensity of the current excited by zinc and iron is smaller. If the quantity of electricity yielded by zinc and iron be 260, that yielded by zinc and copper is 100: when the plates are connected by a wire 50 feet long, the quantity yielded by zinc and iron is 337, and by zinc and copper 18. The resistance of the long wires diminishes, therefore, the quantity yielded by zinc and iron from 100 to 13, and by zinc and

copper, from 100 to 18.-When the plates are connected by a fine wire 2000 feet long, the quantity of electricity yielded by zinc and iron is to that furnished by the zinc and copper as 1000 : 1678. With amalgamated iron, zinc yields a much feebler current than with common iron, (Poggendorff.)

Göttling (Gilb. 28, 475) constructed a powerful pile with plates of iron covered with zinc on one side, and moistened pieces of cloth.

Cadmium is positive towards iron in dilute sulphuric acid, and yields 400 times more electricity, than copper with platinum. Nevertheless, more iron than cadmium is dissolved. (Poggendorff.) [This deserves attention.]

Tin is positive with lead in concentrated aqueous solution of oxalic or tartaric acid, negative in very dilute solutions. (Fechner.)- Tin is positive with iron or copper in dilute acid (De la Rive); and a steel wire consequently remains bright, and loses no weight, when placed in contact with tin under dilute hydrochloric acid. (J. Davy.)

The following are the weights lost by tin balls of equal size placed for an hour in very dilute hydrochloric acid, contained-in vessels of different materials: in vessels of glass or sulphur, 3; of lead, 12; silver, 19; antimony, 34; bismuth, 36; copper, 70; platinum, 85; gold, 201. (Bouchardat.)

Polished lead is positive in dilute acid towards iron and copper, tarnished lead negative. (Yorke.) In dilute hydrochloric or sulphuric acid, iron is, after the first moment, positive towards lead. (Wetzlar,) [Was the lead quite clean?].-Iron, when in contact with lead, dissolves more slowly in dilute sulphuric acid than when alone: after a few days, the iron becomes dull, and covered with sulphate of lead. In dilute hydro

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cic acid, on the contrary, the solution of iron is accelerated by contact ime in both lead. (Runge.) eren miou. In cold dilute sulphuric acid, tin is feebly positive towards lead; eting * slightly negative, when the acid is warm. Towards iron, tin is positive in

cold acid, often slightly negative in warm acid. (Faraday.)

Antimony in dilute sulphuric acid is positive towards bismuth. (Fechner.)

Iron in dilute acid is strongly positive towards arsenic. (De la Rive.)

Nickel in dilute sulphuric acid is positive towards antimony and bismuth. (De la Rive.)

Copper in dilute acids is positive towards silver and platinum; so also is silver towards platinum. (Walcker.)

Gold exerts a scarcely perceptible positive reaction towards platinum in dilute sulphuric acid. (Ritchie.) In dilute sulphuric acid it is positive; in dilute hydrochloric acid, ' negative. (Walcker.)—In a mixture of 1 part oil of vitriol and 100 water, it is at first positive,-then, after several immersions, neutral, and subsequently negative. (Marianini.)

Palladium gives no current with platinum in pure hydrochloric acid, but becomes positive on the addition of nitric acid. (De la Rive.)

Anthracite in dilute sulphuric or hydrochloric acid is negative towards copper, silver, or platinum. (Becquerel.)

Platinum is at first positive towards graphite, neutral after several immersions, then negative. The graphite remains unaltered; but the platinum is rendered positive towards other platinum, losing this property, however, by ignition or immersion in boiling water. Gold and silver exhibit similar relations towards graphite, but in a lower degree. When platinum, gold, or silver is immersed in contact with graphite till it ceases to produce deflection of the needle, and then,-while still remaining in the acid-connected for a short time with zinc, it again becomes positive to graphite. Possibly, when these metals are placed in contact with graphite, a portion of oxygen becomes fixed upon them, and renders them more negative; and when they are connected with zinc, this oxygen is removed by the hydrogen, the latter then accumulating on the surface of the metal: for platinum which has been in contact with zinc under dilute acid is positive towards platinum which has not been so treated. (Marianini.)

Platinum is feebly positive towards peroxide of manganese in dilute acid. (De la Rive).

Pairs of plates of the same size of different metals immersed in very dilute sulphuric acid produce the following deflections of the needle:

"6.0°, with platinum 3.3°. - Tin with copper 5.0°, with silver 4.0°, with gold or platinum 1.0°.-Lead with iron 2.0°, with copper 5-3°, with silver 4:3°, with gold 1.5°, with platinum 2.0°.Iron with copper 3.0°, with gold or platinum 1.0°.—Copper with silver 3.3°, with gold or platinum 0.3°;Silver with gold or platinum 0•3°. The positive metal in each case has its name printed in italics.—These deflections are not in accordance with the theory of contact. The smallest deflections are those obtained with pairs containing gold or platinum ;-it is true that platinum does not conduct so well as silver; but gold conducts better--and yet copper and silver give a stronger deflection than copper and gold. (Marianini.)

Electrical series of perfect conductors in dilute acids, each body of the series being negative with those which precede, and positive with those which follow it:

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