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.

    469/562 (page 445)
    galyanometer even increasing a little under these circumstances. (J acobi.) The development of gas still goes on when the water is subjected to a ote 150 atmospheres, till at length the tube bursts. (Degen, Poyg. 38, 454, Influence of the Relative Volume of the Electrolyte on Decomposition. When the current from two pairs of zinc and platinum excited by dilute sulphuric acid, is conducted by means of two platinum plates into dilute sulphuric acid, the strength of the current is the same, whether the platinum plates are at the distance of six inches from one another or se- parated only by the thickness of a sheet of paper. (Faraday.) [With pure water, a greater difference would probably be found. | The thinner the film of liquid which the current has to traverse, the greater is the deflection produced. The increase of deflection caused by diminishing the thickness of the liquid, is the more considerable as the conducting power of the liquid is less [7. e. as the resistance to the trans- position of atoms is greater]. When, however, by enlarging the platinum plates, the current has been raised to its maximum, the deflection is no longer increased by bringing the electrodes nearer together. (Matteucci.) The distance between the electrodes remaining the same, the deflec- ~ tion is augmented up to a certain point by increasing the height and breadth of the liquid; but when the increase in dimension is carried further, the deflection diminishes. The deflection is stronger when the positive electricity enters by the narrower part of the liquid, and the negative by the wider, than in the contrary case. (Matteucci.) Influence of the Chemical Nature of the Hlectrodes on Decomposition. The greater the tendency of the electrodes to combine with those elements of the liquid which are set free upon them, the more easily does the decomposition takes. place. If the quantity of electricity in the current of a single pair of zinc and copper plates in dilute sulphuric acid be equal to 1000 when the circuit is closed by good metallic conductors, it will amount to the following quan- tities when the current is conducted by the under-mentioned electrodes into the following liquids: zinc plates in water, 0°8; in fuming oil of vitriol, 64°7; in a mixture of 1 part of sulphuric acid and 3 parts water, 85°1;—platinum electrodes in hydrochloric acid, 2°6; in nitric acid, 17-7; in aqua regia, 338°3. Hence it appears that those liquids which do not act chemically on the electrodes offer the greatest resistance. (Fechner.) If the cups a, b (App. 2), contain dilute sulphuric acid, o consisting of zine, p of copper, and ghi of one of the following metals, no hydrogen gas is evolved at the end p when ght consists of platinum, and only a trace when it is formed of gold; next follows silver, then copper, then tin, then iron, and lastly zine, which yields most of all. If, however, the two cups contain ammonia, the deflection is stronger when g/ 7 consists of copper than when it is formed of iron. (De la Rive.) ‘at When the positive electricity of a pair of zinc and platinum is con- ducted by zinc into dilute sulphuric acid, the quantity of the current is the same as when the circuit is metallically closed without the interposi- tion of a liquid. (Faraday: vid. 441.)