Copy 1, Volume 1

Hand-book of chemistry / Translated by Henry Watts.

  • Gmelin, Leopold, 1788-1853
Date:
1848-1872
Catalogue details

Licence: Public Domain Mark

Credit: Hand-book of chemistry / Translated by Henry Watts. Source: Wellcome Collection.

    440/562 (page 416)
    each platinum plate is the same, and equal to that which was before evolved on the platinum plate of the weakest pair. If the rings of all the zinc and platinum plates are immersed in a vessel filled with mercury, the development of gas on the platinum plates again becomes as unequal asin the first case. If every two zinc plates be connected with every two platinum plates, and the 5 double pairs united into a battery, the evolution of gas is the same in all the cells. When 8 pairs are left simple, and connected with one double pair to form a battery, the quantity of gas evolved on the two platinum plates of the double pair taken together, is not greater than that evolved. on each platinum plate of the single pairs. When each of the 10 zinc plates is placed between two platinum plates, the evolution of gas on each double plate is increased nearly two- fold; and part of the gas likewise escapes on that surface of the platinum which is turned away from the zinc. When unamalgamated zinc is used, a great deal of hydrogen gas is evolved upon its surface; but the quantity evolyed on the platinum is the same as when the zinc is amalgamated ; hence the local [pure chemical] action does not interfere with the force of the current. (Daniell.) Sal If several pairs of amalgamated zinc and platinum in dilute sulphuric acid are united into a battery, and the polar wires dipped into dilute sul- phuric acid, the quantity of hydrogen gas evolved in each exciting cell of the battery is exactly the same as that set free in the decomposing cell. When the circuit is imperfectly closed by the interposition of a long thin wire or a liquid conductor, the quantity of gas evolved in all the cells is diminished, but is the same in all; the greater the number of pairs, the less does this diminution in the quantity of hydrogen gas amount to. (Matteucci) Twenty pairs of zinc and copper give the same deflection of 20° as one pair, when the circuit is closed by a wire of sufficient thickness. But when the current is conducted from the poles through a stratum of water, the deflection with one pair amounts to 10°, with 5 pairs to 15°3°, and with 20 pairs to 19°. (Buff.) ‘ One pair of plates gives the same deflection, whether the metals are separated by one or five pieces of cloth saturated with liquid; but when several pairs are united, the deflection diminishes as the thickness of the cloth is increased. The diminution is less however in proportion as the liquid conducts better [#. ¢., exerts chemical action]. Marianini. The following experiments by Binks were made with amalgamated zinc plates and platinum plates of equal size in dilute sulphuric acid. The quantity of zinc dissolved in a given time diminishes as the number of plates is increased, in the following proportion—the first number denoting the number of pairs of plates, the second the loss of zine: 1: 5°7,—2 :3°9 ;—4:3°8,—8 : 3°8,—16 : 3°4,—82 : 3°6,—40 : 3°8,— 48 :2°7. : A similar diminution takes place in the quantity of hydrogen gas evolved, when two pairs of unequal surface are united: a denotes the surface of each of the pairs of the plates, 6 the quantity of hydrogen gas which each would have developed by itself, ¢ the quantity evolved after their union: a 5b c 6 ie 7 1G — a aennnner RENT tT 2S) ee