Sir H. Davy next proceeded, in an elaborate train of ex periments, to ascertain the physical properties of these me tals, to which he gave the names of potassium and sodium, and their chemical relations to other bodies. He examined their fusibility, the power which they possess of conduct ing electricity and caloric, and their specific gravity. Ile afterwards observed their action on water, the acids, sul phur, phosphorus, the metals, oils, and metallic oxides. It is scarcely necessary to remark, that the examination was conducted with the address and dexterity which charac terize all the operations of this distinguished experimen talist. A minute detail of the particulars would be foreign to the object of this article, and strictly belongs to the science of chemistry ; galvanism being no farther connected with these bodies, than as the instrument by which they are pro duced. On this account it will not fall under our pro•, ince to notice the discussions which ensued respecting the na ture of these new metals ; for although it was generally ad mitted that the substances were the bases of the fixed al kalies, and were metallic, yet there were some circum stances in the mode of their formation, which led to the supposition, that they were a compound of a metal and hy drogen ; but this opinion is now abandoned.
The analogy which exists between the properties of the fixed and the volatile alkalies, led Sir H. Davy to apply his powerful means of decomposition to ammonia. The analo gy of properties, however, which causes them to be plac ed in the same class of bodies, scented to be counteracted by the experiments of Berthollet, who, as is well known, had resolved this latter substance entirely into hydrogen and azote. Accordingly the metallic nature of ammonia has not yet been proved, and although Sir H. Davy, in his earlier experiments, conceived that he had procured oxy gen from it, and Berzelius obtained a species of amalgam, by exposing it in contact with mercury to the galvanic in fluence, yet subsequent experiments by Henry, and Gay Lussac and Thenard, appear to explain these appearances on other principles, and to restore the original conclusion, that ammonia is a compound of azote and hydrogen alone. See Phil. Trans. for 1808, p. I.
Sir H. Davy next turned his attention to the earths. He found them more difficult to decompose than the alkalies, and many arrangements were employed without success. The object was, however, at length, to a certain degree, ac complished, by mixing the earth with a metallic oxide, and placing this in contact with a globule of mercut y negative ly electrified, when an amalgar.1 was formed, consisting of the mercury and the metal of the earth employed. In this way it appeared, that a metallic basis had certainly been obtained from the four alkaline earths, to which the names of barium, calcium, strontium, and inagnium, were respec tively applied. The remaining earths, silex, alumine, zir con, and glucine, were still more refractory, probably in consequence of their more powerful affinity for oxygen. No decomposition could be effected by the same means which had been found successful with the alkaline earths ; but it was at length partially accomplished, by keeping the earth in fusion with potash, inducing upon it positive elec tricity, and touching it with a negative wire. In this case
an amalgam was produced, which probably consisted of the metal of the earth employed and potassium. See Phil. Trans. for 1808, p. 233.
The brilliant discoveries of Sir H. Davy, and still more the new and powerful agent which he had introduced into chemistry, could not fail to engage the attention of all those who were interested in the progress of the science. Among these Gay-Lussac and Thenard in France, and Berzelius in Sweden, immediately commenced their ope rations in the application of galvanic electricity to the de. composition of bodies, made many important experiments, and brought to light many new facts. The general result was, to afford an ample confirmation of the statements of our illustrious countrymen in their most important parts, although in some particulars they regarded the subject in a different point of view, both as to the •mode of accounting for the effects, and the consequences which they deduced front them. These discussions, as well as the many new and interesting experiments connected with them, which have completely changed the aspect of many branches of chemistry, and have enlarged our knowledge of the nature of bodies far beyond its former limits, it does not belong to our department to detail. It will be proper, however, to lay before our readers some of the observations that were made by Gay.Lussac and Thenard, on what strictly belongs to galvanism, reserving the consideration of the hypothetical opinions to the second division of the article.
These sagacious experimentalists remark, that, next to the construction of the pile itself, the most important dis covery was made by Hisinger and Berzelius, who found that when the electric current decomposed a neutral salt or an oxide, the oxygen and acid were carried to the posi tive end, and the base to the negative. The application of this principle enabled Sir II. Davy to effect the decomposition of the alkalies. The authors point out the distinction between the electrical and the chemical energy of the pile ; actions which are essentially dissimilar, and which do not exist in the same ratio. They state, that a comparatively few plates, with acid interposed between them, will decompose the al kalies ; while a greater number, with water instead of acid, will not produce this effect, and will yet exhibit a higher electrical tension. The power of the apparatus was found to be nearly in proportion to the strength of the acid em ployed ; and some comparative experiments were insti tuted, for the purpose of comparing the effects of acids, al kalies, and neutral salts. The test which they employed to judge of the quantity of effect produced by the pile, was the amount of gas evolved from a fluid, subjected to the of the wires connected with its two extremities : this they conceived was a more exact measure of its energy than the different lengths of wire which it was capable of consuming.