two hollow brass spheres in opposite electrical states, and each inclosing the bulb of a delicate thermometer. The spheres were placed at the distance of about four inches from each other, and the subject of examination equidistant between them. The general results of the experiments were such as to afford pretty strong proof, that the phenomena were influenced by the known laws of electro-chemical agency. Substances which, during combustion, are changed into acids, were attracted by the positive surface; and those which form products of an alcaline nature, were attracted by the negative surface; and, consequently, the superior temperature of that sphere to which the flame was attracted, was obviously connected with the direction given to the flame by this attraction, and could not be attributable, as Mr Cuthbertson supposed, to the transfer of electric matter. These phenomena were particularly obvious with phosphorus, whether in slow or rapid combustion, and benzoic acid, which were determined to the positive surface, and potassium, camphor, and resinous substances, which were inclined to the negative one The flame of a small stream of olifiant gas, raised the thermometer on the negative side, in one minute, from 60° to 72°; the positive thermometer being raised only from 60 to 62°.

Some of the phenomena observed, were however rather anomalous. The flame of carburetted hydrogen, for example, was entirely and powerfully attracted by the negative surface, and the flame of carbonic oxide was not very evidently attracted by either pole. Mr. B. thinks it not improbable, that the carbonic acid produced during the combustion of carburetted hydrogen, may pass to the positive surface, and that the direction of the flame may be influenced rather by the combustible, than by the product of combustion. This, however, does not appear to us to be a very satisfactory solution of the difficulty. The facts contained in the paper are, notwithstanding, very interesting; they afford strong evidence in favour of the theory of the inherent electrical states of matter. And they confirm in the most decisive manner, the conclusion from Dr. Wollaston's experiments of the identity of the chemical powers of common, and of Voltaic electricity.

An Account of some new Experiments on the Fluoric Compounds; with some Observations on other Objects of Chemical Inquiry. By Sir H. Davy, LL. D. F. R. S. and P. R. I.

The experiments detailed in this communication, tend to confirm the inferences deduced from Sir Humphrey's former experiment on this subject, that pure fluoric acid is, like muriatic acid, a compound of hydrogen united to a base which from its

strong attraction for hydrogen, has not yet been exhibited in a separate form; but which may be detached from its combination with hydrogen by some metallic bodies. Since his former communication, Sir H. has made various attempts to separate the fluoric base by electro-chemical agency; but without success. Fluate of lead when moist, was found to be easily decomposed by ammoniacal gas, and a white powder was separated, which must contain oxygen, since carbonic acid was formed by igniting it with charcoal; but dry fluate of lead was fused in ammonia, without the slightest change being produced; so that the presence of water seems indispensably necessary for the production of oxidated bodies from the fluoric combinations.

Analogous results were obtained by the action of chlorine on silicated fluate of ammonia, and fluo-borate of ammonia. When the salts were moist, or when the gas was not free from vapour, silica and boracic acid were formed in small quantity; but if the presence of water was carefully excluded, these bodies were not produced; and the results were muriate of ammonia, and silicated fluoric gas, or fluo-boric gas and azote. Two points of charcoal were intensely ignited in fluo-boric and silicated fluoric gas, both pure, and mixed with oxygen; but there was no indication of any decomposition. A very small quantity of hydrogen was produced, which Sir H: supposes was disengaged from the ignited charcoal. Pure liquid fluoric acid, was passed over charcoal ignited to whiteness in a tube of platinum; no carbonic acid was formed; but as in the former experiment a minute quantity of hydrogen was produced. Sir H. renewed his attempts to ascertain the composition of some of the fluates, by a repetition of some of his former processes; and their general results lead him to conclude, that the number representing fluorine, is about 33, or less than half that which represents chlorine; which coincides with the conclusions drawn from his former experiments, already published in the Transactions,

Sir H. made some direct experiments to determine the proportions in which oxygen exists in silica; but they were not successful. He ascertained, however, that it requires more than three parts of potassium to decompose one part of silica; and silica it would appear therefore cannot contain much less than half of its weight of oxygen. The attempts made to separate the basis of silica in a pure form, were not perfectly satisfactory, though deserving of notice, as being likely to lead to more successful efforts. Silica was decomposed by passing potassium through it in a heated tube of platinum. The result obtained was alcali, baving a dark-coloured powder diffused through it. This was presumed to be the basis of silica. The whole mass was fused with sulphur, and became ignited, by the combination of the sulphur with the dry alcali. The sulphuret of potash was VOL. V. N. S.

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then dissolved by water; but the dark coloured particles which were diffused through it, acted upon the water of the solution; so that when an attempt was made to collect them upon a filter, they were for the most part converted into silica. Some gas was produced by the action of this substance upon the water, but it does not appear to have been collected and examined.

In another experiment of this kind, the substance was heated. with hydrate of potash; there was a copious effervescence, and silica appeared to be reproduced and dissolved by the alcali. In another instance, the product was heated in a strong lixivium of potash, the solution acquired an olive tinge, but there was scarcely any perceptible effervescence, from which it is probable that the basis of silica, like boron, is soluble in alcaline solutions without decomposing them. Indeed, Sir H. remarks that this substance has in many respects a close alliance to boron. It appears to be neither fusible nor volatile; like boracic acid, its oxide exerts a neutralizing power on the alcalies, and forms like that acid vitreous compounds with the alcaline earths; and like boron, the siliceous basis forms a powerful acid when combined with fluorine. Sir H. thinks it probable that these substances form a distinct class, not allied to the metals, as he formerly supposed, but arranging themselves according to their natural affinities, probably between charcoal and sulphur, and phosphorus.

This paper contains also some additional experiments on chlorine, made with a view to the determination of the still agitated question of its simple or compound nature; but they afford no evidence whatever of its containing oxygen. Sulphuret of lead was kept some time in a state of fusion in chlorine; the results were sulphurane, (Dr. Thomson's liquor,) and plumbane, or muriate of lead, but not an atom of sulphate of lead was formed; which must have been produced if oxygen had been present. Plumbane was heated in sulphuric acid gas, and also in carbonic acid gas, but no change whatever was produced.

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The other facts or remarks on this subject tend to prove that no water is formed by the action of muriatic gas on ammonia and that the small quantity which appears during these experiments, is the minute quantity which is known to exist in these gases, but which is not essential to their existence, nor chemically combined with them.

Some Experiments and Observations on a New Substance which becomes a Violet-coloured Gas by Heat. By Sir Humphry Davy, Knt. LL. D. F.R. S.

The singular substance described in this paper, was discovered by M. Courtois, a manufacturer of saltpetre, at Paris.

He had remarked that some of his metallic vessels were very rapidly destroyed in the processes requisite to extract soda from the ashes of sea weeds. In searching for the cause, he discovered the substance in question, by which he ascertained that the corrosion of his vessels was produced. This substance is obtained very readily from the kelp ashes, after the soda is obtained from them, merely by the action of sulphuric acid. If the acid is concentrated, the heat produced is sufficient to raise the substance in the state of vapour, which is of a fine violet colour, and which when condensed, forms crystals, having the lustre and the colour of plumbago.

Shortly after its discovery, a short memoir was read to the Institute, by Clement and Desormes, describing its principal properties; and it has since engaged the attention of some of the most eminent experimental chemists. They ascertained that its specific gravity is about four times that of water; that it assumes the gaseous state at a temperature below that of boiling water; that it combines with the metals, with phosphorus, and sulphur; and likewise with the alcalies, and metallic oxides; that it forms a detonating compound with ammonia; that it is soluble in alcohol, and still more so in ether; and that by its action upon phosphorus and hydrogen, a compound having the characters of muriatic acid, is formed. Gay Lussac, in another paper read to the Institute, stated that the acid produced by its combination with hydrogen, was a new and peculiar one; and he regarded the substance as allied to chlorine.

In subjecting this body to experimental investigation, Sir H. began by endeavouring to ascertain if argentane (muriate of silver) would be formed by its action upon nitrate of silver. For this purpose, it was purified by distilling it from lime, and when it was added in solution, to a solution of nitrate of silver, a dense precipitate of a pale lemon colour was formed. This precipitate being collected and examined, was fusible at a low red heat, and then assumed a red colour. It was rapidly decomposed by fused hydrat of potash, and a substance having all the characters of oxide of silver, was formed. When this was separated by a filter, the solution being acted upon by sulphuric acid, afforded the peculiar substance. A solution of potash being boiled on the precipitate, afforded the substance when treated in the same manner by sulphuric acid. The precipitate was much more rapidly acted upon by light,

than the muriate of silver.

As these facts rendered it probable that the precipitate was a compound of the newly discovered substance with silver, Sir H. endeavoured to form a direct combination of them with each other. For this purpose, some of the substance was

introduced into the closed end of a curved glass tube, and a portion of silver foil was placed in the upper part of the same tube. The foil was heated nearly to redness, and the vapour of the new substance being passed over it, an immediate combination took place, and a fusible substance was formed, in all its obvious characters the same as that obtained from the nitrate of silver. Supposing the new substance to be capable of decomposition, Sir H thought it most likely to be effected by the action of the highly inflammable metals upon it, or by the action of chlorine, which in general disengages oxygen from its combination with inflammable matter. Some potassium was therefore heated in a small glass tube, and some of the new body in a state of vapour was passed over it; as soon as they came in contact, there was inflammation, and the potassium burnt slowly with a pale blue light. When the experiment was made in a mercurial apparatus, no gas was disengaged. The substance resulting from its combination with potassium, was white, fusible at a red heat, and soluble in water; its taste was peculiarly acrid; and when acted upon by sulphuric acid, it effervesced, and the new substance was disengaged. In this experiment there was evidently no decomposition effected.

It was next exposed to the action of chlorine in a small glass tube. The chlorine was absorbed, and the resulting compound was a yellow solid matter, volatile by heat, and soluble in water, the solution being of a yellowish green colour, and strongly acid. When the solution was acted upon by a solution of potash not in excess, it effervesced and afforded the peculiar substance. The acid formed by this combination with chlorine, reddened vegetable blues by its immediate contact, and soon after destroyed them entirely. The new substance heated in oxygen gas, or brought into contact with red hot hyperoxymuriate of potash, appeared to suffer no change. Sir H. heated the new substance with iron, mercury, tin, zinc, and lead, out of the contact of air: it combined with them without any violent action, and formed compounds fusible at a moderate heat, and volatile at a higher temperature. All these compounds, except that of zinc, which was white, were of different shades of red, brown, and orange; and that with mercury, when crystallized, was a bright crimThe combination with iron, when exposed to the action of an alcaline solution, deposited black oxide of iron; but when heated in a retort with ammonia in the gaseous state, it combined with the ammonia, and the compound volatilized without leaving any oxide. The combination with tin was soluble in water, and had the character of an acid, and it formed combinations with the alcalies without depositing any oxide.

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