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.

    441/562 (page 417)
    #7 anes ; . * ws GALVANIC BATTERY. ; 417 It is remarkable that when the surfaces of the two pairs of plates are very unequal, the quantity of hydrogen evolved on the copper of the larger pair is greater than that evolved on the copper of the smaller. — (Binks. ) | The electric current of a battery ceases when the whole is cooled to — 18° [in consequence of the freezing of the liquid?]; it increases with the temperature, but ceases again at 100°, and recommences with violence on subsequent cooling. It is however considerably increased by heating only half of the battery to 100° (Dessaignes, Ann. Chim. Phys. 24, 203), EB ithis deserves verification|—A battery which at 15° gives a current, capable, when conducted through a watery liquid, of disengaging 223 measures of hydrogen gas in a given time, yields 89 measures in the same time, when heated to 52°. (Despretz, Gilb. 72, 310.) When the current of a trough-battery has diminished, it may be increased almost double by stirring the acid liquid between the zine and copper plates with a feather. (Faraday.) Electrical Tension of the Battery. The tension of the unclosed circuit, as determined by the electrometer, increases directly as the number of pairs. (Volta, Bohnenberger (vd. 57, 846), Singer, Marianini.) It increases as the square of the number of pairs. (Delezennes, J. Phys. 82, 269). In the unclosed circuit, it increases as the square of the number of pairs, and in the closed circuit directly as the number; for the statical effects of a given quantity of electricity, as shown in the open circuit by the electrometer, are to the dynamical effects which the galvanometer exhibits in the closed circuit, in the ratio of the square to the simple number. (Peltier.) The tension, as shown by the electrometer in the unclosed circuit 1s not affected by the size of the plates, but only by their number. When one, pole is connected with the ground, the maximum of tension is the same, whether the battery be charged with river-water, solution of sulphuret of soda, or water acidulated with nitric acid; but in the last case, the maxi- mum tension is instantly attained, more slowly in the second, and most slowly of all in the first. When the battery is insulated, the tension is altogether weaker,—strongest however when the charge is made with river-water, weakest when water acidulated with nitric acid is used: in the latter case, it often vanishes altogether. (De la Rive.) Inthe unclosed . circuit, the nitric acid exerts an oxidizing action, not only on the zine, but. likewise on the copper, thereby giving rise to an opposite current; but when the circut is clesed, the oxidation of the copper ceases. (Buff.) The middle pair of an unclosed circuit of twenty pairs of zinc and copper does not act more strongly on an electrometer furnished with a condenser, than one single pair would. The greater the number of pairs included in the circuit by touching one of them with the condenser and the other with the finger, the stronger is the divergence of the gold leaves. Likewise, when the circuit is closed, but in such a manner that the current is obliged to pass through water—not decomposing it perceptibly—a cer- tain degree of tension is manifest, increasing towards the poles. Even when dilute sulphuric acid is used instead of water, tension is still appa- rent, although the liquid is decomposed; but not when tlre circuit is com- pletely closed by a metallic conductor. Whenever, therefore, an obstacle, such as water, is to be overcome, electricity accumulates in the poles till it acquires sufficient tension to overcome the practenren (Buff.) VOL, I, B