Art. V. Philosophical Transactions, of the Royal Society of London. For the year 1811. Part 1. 4to. pp. 208. Nicol. 1811.

THIS part of the Society's transactions contains ten papers: of which the first is

The Bakerian Lecture. On some of the Combinations of Oxymuriatic Gas and. Oxygene, and on the chemical Relations of these Principles, to inflammable Bodies. By Humphry Davy Esqr. L. L. D. Lec. R. S. F. R. S. É. M. R. I. A. and M. R. I. Read Nov. 15. 1810

In his last communication to the Royal Society, Dr Davy gave an account of the newly discovered facts which Ied him to conclude, that oxymuriatic acid gas was a body which had never been decompounded, but was analogous, in many of its properties, to oxygene. He now presents us with a series of experiments, made with a view to the farther investigation of this interesting problem; and his former conclusions appear to us to receive very strong confirmation, from the facts detailed in the present Lecture.

The first experiments were made with potassium. Dr. D. satisfied himself that, when proper care was taken to separate all moisture from the gas, and from the crust of potash, which forms upon the surface of the metal, no moisture is disengaged during their combination. At the mean temperature and pressure, I grain of potassium combined with 1.1 cubical inch of the gas; and the resulting compound underwent no change by fusion, but possessed all the properties of muriate of potash which had been ignited. The vivid combustion of the alcaline metals in oxymuriatic gas, led him to suppose, that their affinity for it was stronger than for oxygene-which experiment proved to be the case. But before he enters on this subject, he stops to discuss, more fully than he had done before, the nature of the combinations of potassium, and sodium, with oxygene.

After adverting to the different products which he has described to result from the combustion of these metals in oxygene, and in the open air, he notices the conclusions of MM. Gay Lussac and Thenard, who found the last of these, which Dr. D. had suspected to be protoxides, to be peroxides: the one containing three times as much oxygene as potash, and the other 1.5 as much as soda. He states that he has himself confirmed these results, though without being able to ascertain the precise proportions of oxygene in the new oxides,-chiefly in corsequence of the oxidation

of the metal on which the combination is made. Dr. D. endeavoured to remove this source of error, by lining a tray of platina with fused muriate of potash. The peroxide of potassium obtained in this way, was of a bright orange colour, and that of sodium of a darker orange tint. They both gave off oxygene to the action of water and acids; were converted into common alcali, when heated with any metallic or inflammable matter; and thickened the fined oils forming a compound which did not redden turmeric paper, without the presence of water. The pure alcalies, obtained by the combustion of the metals in oxygene, and afterwards heating the products to decompose the peroxide which is formed; are of a greyish green colour, harder than common potash or soda, and of greater specific gravity: they require a strong red heat for their complete fusion, and evaporate slowly at a higher temperature. The addition of a small quantity of water causes them to heat violently, and become white; and when thus converted into hydrats, they are easily fusible and volatile. If the combustion of the metal is made on glass, perfectly freed from metallic oxides, and strongly heated, or if the alcalies are formed from the metais by a very minute quantity of water, their colour is rather white; but in other sensible properties they resemble the alcalies already described, and are very infusible. As water had not been separated from potash which had been ignited, Dr. D. attempted to obtain experimental proof of its existence, by heating 40 grains of ignited potash with 100 grains of boracic acid, which had been kept near an hour in a white heat. When the experiment was finished, the retort had lost 6 grains, and the receiver had gained 5. 8 grains of water, with a little acid in solution. Soda, treated in the same manner, indicated 22.9 per cent. of water; but it was not weighed. When potassium used in the experiment, or potash which had been formed by close combustion, there was not the slightest indication of moisture and he consequently thinks it fully proved, that common potash and soda are hydrats, and that the alcalies formed by the combustion of the metals are the pure oxides free from water.

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After this digression, Dr. D. returns to the consideration of the relative attractions of the oxymuriatic gas, and the oxygene, for the alcaline metals. He heated one grain of potassium, in a retort containing oxygene; and the alcali was afterwards heated to redness to decompose any peroxide which might be formed. It was found to have

combined with half a cubical inch of oxygene; and, when the retort was exhausted and filled with oxymuriatic gas, it became white, and by a gentle heat was converted into muriate of potash,-one cubical inch and of oxymuriatic gas being absorbed, and exactly half a cubical inch of oxygene evolved. In the course of his experiments with these substances he found, that water was separated from the hydrat of potash by the oxymuriatic gas; but that, when dry potash was employed, or mixtures of potash and the peroxide, no moisture was separated, except when the gas contained aqueous vapour. If the heat employed was sufficiently high, the oxygene evolved always corresponded exactly with the quantity previously absorbed by the potassium. When dry potash, formed by the combination of the metal, was exposed to the action of mu riatic acid gas, water was instantly formed, and the alcali was converted into oxymuriatic of potassium; and when the experiment was made with hydrat of potash, which had been heated to redness, water was separated in great abundance, and ten grains gained an increase of weight of 2 grains. The phænomena presented by the action of oxymuriatic gas on soda and sodium, were precisely similar but the quantity of gas absorbed was nearly double. Dr. D. observes, that the new facts, developed by these experiments, coincide very accurately with the theory of definite proportions: and he thinks that the additional light thrown upon the peroxides of the alcaline metals, confirms his former conjecture, that the oxygene in the oxymuriate of potash is in triple combination with the metal and the oxymuriatic gas.

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On the combinations of the metals of the earths, with oxygene and oxymuriatic acid gas. Baryta, strontia, and lime being heated to redness, in oxymuriatic gas, a substance bearing considerable resemblance to a dry muriate, was formed with each,-oxygene being disengaged in the proportion of 4 to 2 of oxymuriatic gas absorbed. attempt was made to form a direct combination of the gas with the metallic bases of the earths. Dr. D. observes that, in the last experiments which he made on the metallization of the earths, by amalgamation, he found, on exposing them to the air, that the baryta which was formed, was not fusible at an intense white heat, and the strontia and lime gave no water when ignited. Berthollet, however, has shewn, that the baryta, obtained from the chrystals of that earth, is a fusible hydia; and Dr. D. obtained

water from baryta procured from chrystals, by heating it with oxymuriatic gas. He found, too, that hydrat of lime was much more rapidly decomposed by oxymuriatic gas, than quick lime,-its oxygene being expelled along with the water. Dry quick lime, heated in a retort with muriatic acid gas, afforded water in great abundance-which Dr. D. attributes, of course, to the hydrogene of the acid combining with the oxygene of the lime.

Dr. D. attempted to decompose muriate of lime, by means of potassium, with a view to obtain calcium; but the extreme avidity of the muriate for water was unfavourable to the success of the experiment; and the result was merely a dark coloured matter, diffused through a vitreous mass, which efferversced with water. The potassium had all disappeared, and the retort had received a heat at which it volatilizes entirely. Results nearly similar were obtained from the muriates of strontia and baryta. Dr. D. supposes, either that the bases of the earths were wholly or par-, tially decomposed, or that the potassium had entered into triple combination with them.

The muriates of magnesia, alumina, and silex being easily decomposed by heat, Dr. D. thought it probable that oxymuriatic gas would not separate their oxygene, and on heating them together no change took place. Gay Lussac and Thenard have shewn that baryta is capable of absorbing oxygene; and, as most of the earths form oxymuriates, Dr. D. concludes, that peroxides of their bases must exist: but he was unsuccessful in his attempts to combine lime with an additional dose of oxygene, by heating it with oxymuriate of potash. The oxymuriate of lime, used by the bleachers, gave out oxygene, when heated, and was converted into a muriate.

On the combinations of the common metals, with oxygene and oxymuriatic Gas. All the experiments on these substances were made in retorts of green glass, furnished with stop cocks, and containing from 3 to 6 cubical inches. All the metals acted upon, except silver, lead, nickel, cobalt, and gold, burnt in the gas; and the volatile ones with flame. The products resembled, in particular instances, the known combinations of some of the metals with muriaite acid,-such as the butter of antimony, Libavius's liquor, &c. In other instances, the combinations had not been obtained before. Thus the compound of oxymuriatic gas and arsenic, was a dense, limpid, highly volatile fluid, a non-conductor of electricity,

and of high specific gravity, which, on the addition of water, gave arsenic and muriatic acid, With iron the result was a substance of a bright brown colour, having a metallic lustre, and iridescent, like the iron ore of Elba: it volalitized at a moderate heat, filling the vessel with beautiful minute chrystals of extraordinary splendour, and collecting in brilliant plates: and when acted upon by water, it gave the red muriate of iron. When the metallic oxides were acted upon by the oxymuriatic gas; those of lead, silver, tin, antimony, bismuth, and tellurium, were decomposed at a heat below redness, but the oxides of the volatile metals more readily than the fixed ones. Those of cobalt and nickel were scarcely acted upon at a dull red heat. The red oxide of iron was not changed at a strong red heat the black oxide was decomposed at a much lower temperature. The arsenical acid was unchanged in a high temperature, but the white oxyd was easily decomposed. In those instances in which oxygene was given off, the quantity exactly coincided with that which had been absorbed by the metal. It was not however given out in every

instance.

General conclusions and observations, illustrated by experiments.

'Oxymuriatic gas combines with inflammable bodies to form simple binary combinations; and in these cases, when it acts upon oxides, it either produces the expulsion of their oxygene, or causes it to enter into new combinations. If it be said, that the oxygene arises from the decomposition of the oxymuriatic gas, and not from the oxides, it may be asked, why it is always the quantity contained in the oxide, and why in some cases, as those of the peroxides of potassium and sodium, it bears no relation to the quantity of gas? If there existed any acid matter in oxymuriatic gas, combined with oxygene, it ought to be exhibited in the fluid compound of one proportion of phosphorus, and two of oxymuriatic gas: for this, on such an assumption, should consist of muriatic acid (on the old hypothesis, free from water) and phosphorous acid; but this substance has no effect on litmus paper, and does not act under common circumstances, on fixed alcaline bases, such as dry lime or magnesia. Oxymuriatic gas, like oxygene, must be combined in large quantities with peculiar inflammable matter, to form acid matter. In its union with hydrogène, it instantly reddens the driest litmus paper, though a gaseous body. Contrary to acids, it expels oxygene from protoxides and combines with peroxides. When potassium is burnt in oxymuriatic gas, a dry compound is obtained. If potassium combined with oxygene is employed, the whole of the oxygene is expelled, and the same compound is formed. It is contrary to souud logic to say, that this exact quantity of oxygene is given off from a body not known to be compound, when we are certain of its existence in another; and all the cases