There were evident sources of error, indeed, in some of these experiments ; and the conclusions respecting the real composition of the alkalis were never regard ed as very satisfactory by chemists ; though it appeared highly probable, that one or other of the component principles of ammonia, that hydrogen or nitrogen en tered also into the composition of the other alkalis. But no analogy had ever suggested a suspicion, that oxygen, so long taken for the principle of acidity, was also the only principle common to the alkaline bodies ; or that these, like the acids, were compounds of corn 1,ustible bases and oxygen. Yet that this is the nature and composition of the alkalis, now appears to be fully established, by the late surprising and important dis coveries of the celebrated Mr Davy, who has succeed ed in decomposing the fixed alkalis, by cubjeetixig them to the action of the galvanic pile, and ascertained them to be formed from the union of oxygen with highly com bustible metallic bases. It appears from Mr Davy's experiments, 1st, That if dry potass, or soda, having its surface slightly moistened to render it a conductor, be placed on an insulated disc of platina, of gold, of any metal, of plumbago, or even of charcoal, co. netted with the negative wire of the galvanic apparatus, and the positive wire applied to the upper surface of lie alkali, a violent action takes place, with effervescence from this surface, occasioned by a rapid discharge of pure oxygen gas, while from the lower, or negative suriace, there emerge small brilliant globules perfectly resem bling those of quicksilver ; and, 2dly, that these globules rapidly attract oxygen from the atmosphere, or from pure oxygen gas, and reproduce the alkali from which they were obtained ; and that when heat is applied to them with oxygen gas in close tubes, they burn rapidly with a brilliant white flame, absorb the gas, without giving out any thing, and are converted into alkalis, the potass metal always forming potass, and the soda metal, soda. Thus, the composition of the fixed alkalis is satisfactorily demonstrated both by analysis and synthe sis. To these new discovered metallic bases Mr Davy has given the names of potassium and sodium. Both have the lustre and the distinguishing chemical proper ties of metallic bodies, with which they have therefore been classed, though in one of their physical proper ties they are very different. For these are amongst the
lightest of solid or fluid substances ; the specific gravity of potassium being to that of water as 6 to 10, that of sodium as 9 to 10. Potassium, at the temperature of 32°, is crystallized, at 50° malleable, and at 60° more fluid than mercury. Sodium is not quite so fluid ; it melts only at 120', and its fluidity is perfect at The affinity of both for oxygen is so great, that they at tract it from, and decompose, most bodies containing it. They burn spontaneously in oxymuriatic acid gas ; de compose and thus discover the smallest quantity of water in alcohol, xther, or oil ; decompose also the sulphuric and nitrous acids, seize the oxygen of one portion of acid, and are converted into alkalis, which combine with the remaining acid, and form sulphates and nitrates ; and they amalgamate with mercury and other metals. Potassium effects these decompositions with more rapidity and brilliancy than sodium does. From several experiments approximating in general result, Alr Davy concludes, that the alkali potass is composed of six parts of potassium and one of oxygen ; soda of seven parts of sodium and two of oxygen.
Having thus discovered that oxygen was the common principle of the fixed alkalis, there was every reason to infer that it entered also into the composition of ammo nia ; and a number of satisfactory experiments instituted by Mr Davy, with the view of determining this, have enabled him to conclude, that ammonia does in truth contain from seven to eiglitfier cent. of oxygen.
The prosecution of these experiments has already, we understand, discovered to Mr Davy the nature and com position of the alkaline earths, that these too are com posed of combustible bases and oxygen. In this case, we must, with the French chemists, reckon at least five alkalis,—potass, soda, ammonia, barytes, and strontites.
These results, not yet sufficiently familiarized, and at war with all our late anticipations of the nature and corn position of the alkalis, still surprise us. But we must now conclude, that the basis of the pure and combura ting part of the atmosphere is not less alkaligen than oxy gen, nay, that oxydes, acids and alkalis are alike composed of combustible bases and oxygen. See Phil. Trans. for 18u8, Part I. and Nos. 89. and 90. of Nichol sons Journal, and CHEMISTRY. OW