Sir H. Davy, by the action of 8 grains of potassium on water, ob tained, on an average, .9 cubic inches of hydrogen gas, showing that 42 cubic inches, (= 1.61 grains) of oxygen had combined with the metal. Berzelius investigated the composition of potash, by exposing an amalgam of potassium and mercury, containing known proportions of those metals, to water; saturating the potash with muriatic acid; and determining its weight by the muriate potash formed. The following table shows the proportions of potassium and oxygen in 100 grains of potash, as deduced from these different authorities. One hundred grains of potash contain, If deducted from the atomic theory, the true proportions should be 85 of potassium to 15 oxygen, numbers very near those originally obtained by Sir H. Davy. It is probable, indeed, that sources of inaccuracy may exist in the experiments, sufficient to account for this small deviation from theory; and that potash is a compound of 1 atom of potassium weighing 42.5 with 1 atom of oxygen weighing 7.5. Hence the weight of the atom of potash will be 50; and an atom of water (8.5) being added, the atom of hydrate of potash will weigh 58.5. It is doubtful whether the grey compound (mentioned in § v). be a true sub-oxide of potassium, or merely a mixture of potash with po tassium. If the former, it must consist of two atoms of potassium (85) with one atom of oxyged (7.5-92.5. But the latter view of its nature is the most probable one. The composition of the orange oxide cannot be assigned, from the quantity of oxygen, absorbed in the experiments, by which it is produced ; for in eight results, obtained by Gay Lussac and Thenard, there is not a sufficient agreement to decide this point. It seems probable that the oxygen, which converts potassium into this substance, is twice that which converts it into potash; and that the orange oxide consists of 1 atom of potassium 42.5, +2 atoms of oxygen 15, which would make the weight of the atom of or ange oxide 57.5. = = Potassureted Hydrogen Gas. This name I would propose for the solution of potassium in hydrogen gas, which, it has already been stated, results from the action of potassium on water, and, and as appears from Sir H. Davy's exper iments, may be formed, directly, by heating the metal in hydrogen gas. A large portion of potassium is thus dissolved; but the greater part precipitates on cooling. This gas is spontaneously inflammable in the atmosphere; burns * 80 Ann, de Chim, 245. with a very brilliant light, which is purple at the edges; and throws off dense vapours of potash. It loses its inflammability by keeping; is heavier than hydrogen gas; and is very dilatable by electricity. Besides the gas, which is spontaneously combustible, there is also, according to Sementini, another compound of potassium and hydrogen, which is not possessed of this property, and probably contains a less proportion of the combustible metal. Gay Lussac and Thenard* have succeeded, also, in forming a solid compound of potassium and hydrogen. The process consists in heating the metal in hydrogen gas; and the only difficulty is to regulate the heat, for a temperature decomposes the compound. The flame of a spirit lamp, applied to potassium, in a retort filled with hydrogen gas, occasions an absorption of the gas, and the formation of a solid hydruret of potassium. The colour of the substance is grey; it is destitute of metallic lustre; and is infusible. It is not inflammable, either in air or in oxygen gas at common temperatures, but burns vividly at a high one. When strongly heated in a close vessel, it is totally decomposed; all the hydrogen it contains is liberated in the state of gas; and the potassium remains. When brought into contact with heated mercury, hydrogen gas is evolved, and an amalgam of potassium and mercury is produced. Nitrogen gas has not, at any temperature, any action on potassium. ART. 4.-Sodium. The base of soda agrees, in many of its properties, with the base of potash, and exerts on several bodies a similar action, with the obvious exception that the results are compounds of soda instead of potash. Thus with nitric acid it affords nitrate of soda; with oxy-muriatic acid, muriate of soda. In this place, therefore, I shall descride only such of its properties as are peculiar to and characteristic of it. I. SODIUM, at common temperatures, exists in a solid form. It is white, opaque; and, when examined under a thin film of naphtha, has the lustre and general appearance of silver. It is exceedingly malleable, and much softer than any of the common metallic substances. When pressed upon by a platinum blade with a small force, it spreads into thin leaves; and a globule of th orth of an inch in diameter is easily spread over the surface of a quarter of an inch. This property is not diminished by cooling it to 32° Fahrenheit. Several globules, also, may, by strong pressure, be forced into one; so that the property of welding, which belongs to platinum and iron at a high degree of heat only, is possessed by this substance at common temperatures. II. It is lighter than water. As near as can be determined, its specific gravity is as 0.9348 to 1. * Recherches, i. 176. III. It is much less fusible than the base of potash. At 120° Fahrenheit, it begins to lose its cohesion, and it is a perfect fluid at about 180°. Hence it readily fuses under heated naphtha. IV. Its point of vaporization has not been ascertained; but it remains fixed, in a state of ignition, at the point of fusion of plate glass. V. When SODIUM is exposed to the atmosphere, it immediately tarnishes, and by degrees becomes covered with a white crust of soda, which deliquiates more slowly than that formed on potassium. VI. It combines with oxygen, slowly and without luminous appearance, at all common temperatures. When heated, the combination becomes more rapid; but no light is emitted till it becomes nearly red hot. The flame, which it then produces, is white, and it sends forth bright sparks, exhibiting a very beautiful effect. In common air, it burns with a similar colour to charcoal, but of much greater splendour. VII. When thrown into water, it produces a violent effervescense and a loud hissing noise; it combines with the oxygen of the water to form soda; and hydrogen gas is evolved, which does not, however, as in the case of potassium, hold any of the alkaline base in solution. Neither can sodium be made to dissolve in hydrogen gas, by being heated in contact with it. When thrown into hot water, the decomposition is more violent, and in this case a few scintillations are generally observed at the surface of the fluid; but this is owing to small particles of the base, which are ejected from the water, sufficiently heated to burn in passing through the atmosphere. VIII. Its action on alcohol, ether, volatile oils, and acids, is similar to that of potassium; but with nitric acid a vivid inflammation is produced. IX. Sodium appears to be susceptible of different degrees of oxydation. 1st. When it is fused with dry soda, a partition of oxygen takes place between the alkali and the metal. A deep brown fluid is produced, which becomes a dark grey solid on cooling. This substance is capable of attracting oxygen from the atmosphere, and of decomposing water, by which it is again converted into soda. The same oxide of sodium is formed, by fusing this metal in tubes of plate glass. It is of a greyish colour, destitute of lustre, brittle, and gives hydrogen when acted on by water, but less than an equal weight of sodium. It may, however, be doubted, whether this is a compound of sodium and oxygen, or merely a mixture of the metal with soda. 2d. The second oxide of sodium (or first, if the one which has been just described be only a mechanical mixture) is soda. It may be formed by burning sodium, in a quantity of air containing just oxygen enough to convert the metal into alkali. It is of a grey colour; of a vitreous fracture; and requires a strong red heat for its fusion. Water is absorbed by it with violence, and converts it into hydrate of soda. 3d. The orange oxide of sodium may be formed, by burning the metal with an excess of oxygen. It is of a deep orange colour, very fusible, and a non-conductor of electricity. When acted on by water, its excess of oxygen escapes, and it becomes soda. It deflagrates with most combustible bodies. X. There is scarcely any difference between the visible phenomena attending the action of the base of soda, and that of potash on sulphur, phosphorus and the metals. The sulphuret of sodium has a deep grey colour; the phosphuret resembles lead. Added to mercury in the proportion of th, it renders that metal a fixed solid of the colour of silver, and the combination is attended with a considerable degree of heat. This amalgam seems, like that of potassium, to form triple compounds with other metals, and even with iron and platinum, which remain united with the mercury, when it is deprived of the new metal by the action of air. The proportions, in which this base unites with oxygen to form so da, were investigated by the methods already described in the article Potassium. The results of Sir H. Davy; of Gay Lussac and Thenard; and of Berzelius, are given in the following table : Per Davy (1807) 100 soda contain Ditto (1811) Oxygen. 22.3 Sodium. 77.7 The proportions that would best accord with the atomic theory, are 77.5 of sodium to 22.5 of oxygen; for this last number agrees with the weight of three atoms of oxygen. And on the supposition that soda is a compound of 1 atom of sodium x 1 atom of oxygen, by dividing 77.5 by 3 we should obtain the weight of the atom of sodium, viz. 25.8. In this case, the atom of soda would weigh 33.3, and the atom of hydrate of soda 41.8. The number assumed by Dr. Wollaston to represent sodium, (oxygen being 10) is 29.1; and soda will, therefore, be denoted, on his scale, by 29.1 × 10 39.1. The peroxide Dr. Thomson is disposed to consider as a compound of two atoms of sodium with three atoms of oxygent. = SECTION II. Lithia or Lithina. THE discovery of this new substance, which dates only from the commencement of the present year, is due to the skill and sagacity of M. Arfvredson, a pupil of Berzelius. In the analysis of a mineral called Petalite, (first distinguished as a new species by M. D'Andrada, who found it in the mine of Uto, in Sweden), about 3 per cent. of an alkali was obtained, which M. Arfvredson at first supposed to Ann. of Phil. x. 100. 80 Ann. de Chim. 251. VOL. I-B b be soda. On more accurate examination, however, the new substance displayed properties, entirely distinct from those of either soda or potash, especially in possessing the power of neutralizing a much greater quantity of the different acids than either of those alkalies; in which respect it even surpassed magnesia. To distinguish it from the two other fixed alkalies, both of vegetable origin, it received the name of lithion; and this term, to suit the analogy of the other alkalies, was afterwards converted into lithia or lithina. The proportion of lithina in petalite has since been found to be 5 per cent.; and from some very pure pieces of that mineral, Vauquelin has extracted even 7 per cent. M. Arfvredson has discovered it, to the amount of 8 per cent. in triphane or spodumene, a mineral which is not so scarce as petalite; and, to the extent of 4 per cent. in crystallized lepidolite. The process employed by him has not been described; but it probably consisted in fusing the mineral with twice or three times its weight of potash; dissolving the fused mass in muriatic acid; evaporating to dryness; and digesting in alcohol, which takes up scarcely any thing but a compound of the new earth with muriatic acid. By evaporating a second time to dryness, and again dissolving in alcohol, the muriate of lithina is obtained pure. Vauquelin extracted it from petalite by the intervention of nitrate of barytes, employed, probably, in the manner which will be described in the chapter on the analysis of minerals. The muriate of lithina may be decomposed by digestion with carbonate of silver; and the solution of the carbonate, being decomposed by lime or by barytes, yields a solution of pure lithina, which may be evaporated to dryness out of contact with the air, from which it rapidly imbibes carbonic acid. Pure lithina is very soluble in water, and, like the other alkalies, has an acrid, caustic taste. Like them also, it changes vegetable blue colours to green. When heated in contact with platinum, it fuses, and then acts on the metal. That it agrees with the other alkalies in containing a metallic base, has been proved by Sir H. Davy, who applied the power of a galvanic battery to a portion of the carbonate, fused in a platinum capsule. On rendering the platinum positive, and bringing a negative wire to the surface of the fused carbonate, the alkali was decomposed with bright scintillations; but the reduced metal burned again so rapidly, that it was only observed to be of a white colour and very similar to sodium. From analogy, it has received the name of lithium. The proportion, in which this metal unites with oxygen, has, of course, not been determined by direct experiment; but it has been deduced by Vauquelin, from an analysis of the sulphate of lithina, and the application of the law that the proportion between the oxygen of sulphuric acid, and that of the bas ses which it saturates, is as 3 to 1", to be as follows: |