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.

    484/562 (page 460)
    slightly soluble, could be directly weighed;—with benzoate of lime, in which case the lime also could be weighed ;—and with benzoate of zinc, in the case of which, the benzoic acid and the metallic zinc were weighed, ‘and no evolution of hydrogen gas took place. . [The theory which regards sulphate of soda as Na S$ O* certainly affords the simplest explanation of its electrolysis. Since, however, many weighty reasons may be urged against the adoption of this hypothesis, the following explanation may for the present be admitted. Sulphate of soda is Na O,S O*; decomposition by the electric current is exerted only on the soda (since, by Faraday’s law, S O? is incapable of direct decom- position). Sodium separates at the negative pole, where it decomposes water and yields soda and hydrogen gas. The oxygen which was com- bined with the sodium is transferred, together with the sulphuric acid, to the adjacent atom of sodium. Anatom of oxygen is set free at the positive pole; and since the sodium which was combined with it goes towards the nega- tive pole, the sulphuric acid is set free by secondary action,—or rather it passes from its state of combination with soda into that of combination with water. In the case of sulphate of copper, &c., similar actions take place, excepting that the metal liberated by the current does not decom- pose water. ‘The decomposition of oxygen-salts of ammonia is most satis- factorily explained by adopting the ammonium theory of Berzelius, accord- ing to which, sulphate of ammonia, for example, which always contains water, isto be regarded as sulphate of oxide of ammonium (N H*O,§ 0°). The electric current decomposes the oxide of ammonium, just as it does a metallic oxide, into oxygen and ammonium, and the latter is resolved into hydrogen gas which escapes, and ammonia which remains in solu- tion.— According to this view, the direct action of the electric current is confined to the decomposition of metallic oxides, and the transference of the acid from the decomposing oxide to the water is merely a consequence of this action. (Hess’s Observations on Daniell’s Theory—vid. Pogg. 53, 505.)]. . When two salts, which do not precipitate each other, are dissolved together in water, their acids are simultaneously transferred to the positive, and their bases to the negative pole. (H. Davy.) Iron acting as anode in aqueous solutions of oxygen-salts, evolves oxygen gas, Just as platinum does, without oxidating—even. when it is immersed in the liquid before the rest of the circuit is closed. (Schén- bein. moistened cup of Carbonate of Ammonia, filled with mercury, yields ammoniacal amalgam, just as sal-ammoniac does (p. 456). (Seebeck, JV. Gehl. 5, 482, H. Davy.) Fused Borax (Na O, 2 B 0°) yields oxygen gas at the anode and boron at the cathode. Now, since fused boracic acid is not decomposible by the electric current, the separation of the boron must be attributed to indirect action; the current resolves the soda into oxygen and sodium—and the latter separates boron from the boracic acid, (Haraday.)—Fused Quadro- borate of Soda (Na O, 4 B 0%) conducts and shows signs of decomposition, but evolves gas at both poles: it therefore contains water. (Faraday.) Fused Borate of Lead is easily decomposed, yielding oxygen gas and metallic lead. (Faraday.) , The electric current resolves ordinary Phosphate of Soda in a state of solution into soda and phosphoric acid. (Davy.) Fused Acid Phosphate of Soda (Na O, P 0’) conducts and is decomposed; hydrogen gas, how- ever, appears at the cathode, showing that water is present. (Faraday). —