The uncommon merit of this paper has induced us to give a copious abstract of its contents. It may be regard. ed, not only as giving rise to some of the most important experiments and discoveries that have occurred in the his tory of modern science ; but as leading to the establish ment of a new train of reasoning, and to a new theory, respecting the action of bodies upon each other, and the connexion which subsists between the different branches of natural philosophy. The general principle being clear ly established, the consequences were comparatively ob vious, and the skill and ingenuity, which Sir H. Davy af terwards manifested, in the contrivance and execution of the experiments, which are next to be related, although attended by such brilliant results, are really less merito rious, than that profound insight into the operations of na ture, by which they were suggested. Highly, however, as we appreciate the merit of Sir H. Davy, we think it pro per to remark, that the views suggested by Hising,er and Berzelius must be regarded as leading to the theory that was so amply detailed and so firmly established by our illustrious countryman. See Phil. Trans.. for 1807, I.
About a year after the reading of the above paper, Sir II. Davy presented a second to the Royal Society, in which he most happily applied his hypothesis to practice, and succeeded in solving the problem, which had so long re mained involved in obscurity, respecting the composition of the fixed alkalies. After encountering some difficulties in the arrangements of the operation, the grand object was at length accomplished in the following manner. " A small piece of pure potash, which had been exposed for a few seconds to the atmosphere, so as to give conducting power to the surface, was placed upon an insulated disc of platina, connected with the negative side of the battery, of the power of 250 of 6 and 4, in a state of intense activity ; and a platina wire, communicating with the positive side, was brought into contact with the upper surface of the alkali. The whole apparatus was in the open atmosphere. Under these circumstances, a vivid action was soon observed to take place. The potash began to fuse at both its points of electrization. There was a violent effervescence at the upper surface ; at the lower, or negative surface, there was no liberation of elastic fluid ; but small globules, hav ing a high metallic lustre, and being precisely similar in visible characters to quicksilver, appeared, some of which burst with explosion and bright flame, as soon as they were formed, and others remained, and were merely tar nished, and finally covered by a white film, which formed on their surfaces." These globules proved to be the substance of which the author was in search, and were found to be a peculiar in flammable body, possessed of very singular properties, which constituted the base of potash. By employing a si
milar kind of process, a substance was procured from soda, which exhibited properties of an analogous nature, and which was the basis of the mineral, as the former was that of the vegetable alkali.
The author then proceeded to examine the properties of these bodies, and by a masterly train of experiments, sim ple yet conclusive, he demonstrated that they are metals ; that they have every quality which is deemed essential to characterise this class of substances, and that the alkalies are oxides of these metals. The theory of the decompo sition of the alkalies, by means of the galvanic apparatus, is sufficiently obvious, and follows as the direct conse quence of the facts that had been previously established. In all the decompositions that had been effected by the electrical influence, combustible substances were develo ped at the negative wire, while oxygen was produced or evolved at the positive termination. That this was the case with the alkalies, was not only rendered probable by the result of the process, but was afterwards proved by sub sequent experiments. " When solid potash or soda, in its conducting state, was included in glass tubes, furnished with electrified plating wires, the new substances were ge nerated at the negative surfaces ; the gas given out at the other surface, proved by the most delicate examination, to be pure oxygen ; and unless an excess of water was pre sent, no gas was evolved from the negative surface." The experiments by synthesis confirmed the results of those by analysis. The new metallic bodies were convert ed into potash, by exposure to the air, and it was found that this depended upon the oxygenous part of it. When the globules were placed in contact with oxygen, they com bined with it, and were covered with an alkaline crust. Sir H. Davy observes very justly, " that in these facts there is the same evidence for the decomposition of potash and soda into oxygen and two peculiar substances, as there is for the decomposition of sulphuric and phosphoric acids and the metallic oxides, into oxygen and their respective combustible bases." The two components of the alkalies obey the general law which was laid down in the former paper ; the metallic or combustible base is attracted by the negative extremity of the apparatus ; and perhaps repell ed by the positive ; while the oxygen, which reduces it to the state of an oxide, follows the contrary order. In the recomposition of the alkalies, the substances exert their natural affinities ; according to circumstances, either sim ple oxidation is produced, or a more rapid combination, attended with the extrication of heat and light.