more readily. The air of the retort was so impregnated with the vapour of this metal that it almost suffocated me.

The crystals themselves had an odour so strong, that it was impossible to breathe near them without a feeling of pain.

The osmium which had not been volatilized gave out likewise a very striking odour; but I suppose that it owed this property to a portion of the air impregnated with oxide, which it had imbibed during the cooling. This residue only weighed 0.35 gramme, and the quantity of osmium sublimed was far from completing the gramme of osmium employed; because a portion of it had passed into the water of the receiver, being carried hither by the air.

From the result of this operation it appears that oxide of osmium is formed only in proportion to the quantity of air in contact with it. This is conformable to what we know of the oxidation of the other metals.

Yet I am induced to believe that the white oxide formed in this case is not entirely owing to the air of the vessel; for it is formed and volatilized at a temperature so low, that we can hardly conceive how the combination should take place.

I am rather disposed to believe that the osmium as it is precipitated by zinc, still retains a small quantity of oxygen, which when assisted by a gentle heat, unites itself to a portion of the metal and renders it more volatile.

The following observation seems to confirm this idea. When the osmium is precipitated from its solution by means of zinc, and washed several times with water, even acidulated with sulphuric acid, it exhales no odour, as long as it is cold; but if it be exposed to a heat of from 97° to 104°, it exhales the odour during some time.

But the strongest proof is, that osmium which has furnished oxide by distillation, does not furnish any more at the same temperature, although the same quantity of air be present.

§ II. Examination of the Oxide of Osmium.

This oxide is white, transparent, and very brilliant; its taste very strong and caustic, has some analogy with that of the volatile oils, and particularly with that of oil of cloves. Its odour is equally insupportable. It is more fusible than wax; flexible like it, and exceedingly volatile. When placed in contact with animal or vegetable bodies, it blackens them, especially if it be moist. It is very soluble in water, and the solution becomes blue by nutgalls and many other vegetable substances.

§ III. Action of Oxymuriatic Acid.

Into a flagon containing about half a litre (30.5 cubic inches) into which I had put a gramme of osmium, I passed oxymuriatic acid gas, the surplus of which was received in a solution of potash. Soon after the osmium came in contact with the gas, it appeared

to melt, assuming a very beautiful and intense green colour. At last it dissolved entirely, and formed a small quantity of a brownish-red liquid. The solution of potash assumed a yellow colour, and an odour of osmium mixed with that of oxymuriatic acid.

When I opened the flagon containing the solution of which I have just spoken, there issued out a dense white vapour, having an insupportable odour of osmium and oxymuriatic acid. To be able to separate this liquid from the flagon without losing much of it, I mixed it with a quantity of water, and subjected it to the following experiments.

1. A drop or two of this solution let fall into a glass of water, assumed a very deep blue colour on adding infusion of nutgalls. 2. When a plate of zinc was put into the solution, it soon passed to blue, and black flocks precipitated.

I may remark, that the green colour analogous to that of oxide of chromium, which the osmium assumed at the instant of its solution, may proceed from a mixture of the liquid, which is reddishyellow, with a portion of the metal which I suppose to be blue. And, in fact, in proportion as the solution goes on, the green colour becomes weaker and disappears entirely, to give place to reddish-yellow.

When osmium is mixed with water, in order to be dissolved in oxymuriatic acid, it does not become green; but forms at once a yellowish-red liquid.

If ammonia be put into this solution till the acid is saturated, a brown precipitate in flocks falls down, small in quantity, and the liquid passes to a pure yellow, preserving the odour peculiar to

osmium.

This precipitate consists almost entirely of iron, coming no doubt from the zinc.

Action of common Muriatic Acid and Osmium.

Osmium dissolves in muriatic acid when assisted by a gentle heat. The solution begins by being green; but it soon becomes reddishyellow. If to the muriatic acid we add some drops of nitric acid, the solution takes place more readily, so that we scarcely perceive the transition from green to reddish-yellow.

During these solutions a great deal of osmium is always volatilized, even when they are made without the assistance of heat, as is shown by the experiment with oxymuriatic acid.

At the request of Sir H. Davy, 1 endeavoured, but in vain, to unite osmium with iodine. When the mixture of the two bodies was heated in a glass tube, the iodine separated in the form of violet vapours, which attached themselves to the upper parts of the tube, while the osmium remained at the bottom without having undergone any change.

The facility with which osmium dissolves in acids, is, I conceive, a certain proof that in crude platinum it is united to some substance

which protects it from the action of these menstruums. This substance can only be iridium, since it is it which resists solution most obstinately.

The combination of the oxide of osmium with the alkalies, dissolved in water, has a yellow colour.

Though the oxide of osmium does not present acid characters, yet it appears that it combines with the alkalies, and that it is in some measure fixed by this combination. In fact, if it were not so, this metal would escape entirely when the black powder is treated in crucibles with potash or nitre at a red heat.

What gives a certain degree of force to this opinion is, that the addition of any alkali whatever to the aqueous solution of osmium very much diminishes the odour, which again becomes powerful, when the alkali is neutralized by an acid.

The small quantity of osmium which I have been hitherto able to procure, and its great oxidability, have not enabled me to examine if it would unite with sulphur, phosphorus, and the other metals; but these combinations never can be any thing else than mere objects of curiosity.

The characteristic properties of osmium are to oxidate at a low heat, and to form an oxide exceedingly volatile, odorous, and fusible; crystallizable, soluble in water; the solution of which becomes blue by the infusion of nutgalls, and by the immersion of a plate of zinc finally, the property of forming yellow combinations with the alkalies.

ARTICLE XII.

Proceedings of Philosophical Societies.

ROYAL SOCIETY.

On the 9th of November the Society met for the first time after the long vacation. A paper by Sir H. Davy on the fire-damp in coal-mines was read. The author had been invited by Dr. Grey to examine the subject, in order to discover, if possible, some method of preventing those explosions which of late years have proved so fatal to the lives of the colliers. He accordingly visited several of the mines, and analyzed the pure gas collected from a blower. He states, as Mr. Longmire had done before him (Annals of Philosophy, vi. 172), that this gas is extricated from the crevices of the coals; and he found that when a large piece of coal was broken to pieces under water, inflammable gas was given out. The result of his analysis of the gas was precisely the same with the previous result obtained by Dr. Henry (Nich. Jour. xix. 149), that it was pure carbureted hydrogen gas. It required twice its bulk of oxygen gas to consume it, and nearly its own bulk of carbonic acid gas.

This is characteristic of carbureted hydrogen, as both Mr. Dalton and myself have ascertained. He found the specific gravity to be 0.639, but his specimen was mixed with common air. I have shown the true specific gravity of this gas to be 0.555 (Wernerian Memoirs, i. 508).

He found it much less combustible than other combustible gases. Iron heated to whiteness does not set it on fire. It requires actual flame. This fact has induced him to propose a lantern made airtight, with a hole below to admit air, and one above to act as a chimney, as a complete security against the explosion of the firedamp in coal-mines. He found that when a mixture of common air and carbureted hydrogen gas, in such proportions as to explode, is let up into such a lantern, the flame increases, so as nearly to fill the lantern, and then the lamp goes out. He conceives that whenever in a coal-mine the air is mixed with carbureted hydrogen to the exploding point, that such lamps would go out, and no explosion would follow. But such an experiment would be very hazardous. The fact is, that in such a case the gas, within the lantern burns, and of course extinguishes the lamp; but in all probability the gaseous combustion would extend itself through the holes in the lantern, which are filled with gas at the exploding point, and set fire to the whole mixture in the mine. This would certainly happen sometimes, if not always; so that the lantern of Davy would furnish no certain security to the miners. The lamp of Dr. Clanny, if properly improved, is a much safer contrivance, and might be made equally cheap.

I ascertained that the limits of the explosion of this gas were 12 volumes of air and one of gas, and six volumes of air and one of gas. As far as I could understand Sir H. Davy's experiments, they led nearly to the same result. He succeeded in exploding a mixture of this gas and common air by electricity. I could not succeed in this, not having, it seems, hit upon the exploding proportions, though I tried a great many between the two limits.

Sir H. Davy constructed likewise lanterns with valves to prevent the escape of gas from the lantern when it explodes. This would certainly render the lantern safe, provided it can be constructed so as to allow the lamp to burn.

On Thursday, Nov. 16, an appendix to Sir Humphry Davy's paper was read. He found that the addition of 4th of carbonic acid or of azote to the exploding mixture of fire-damp and air prevented the explosion.

A paper by Mr. Daniel on Solutions was likewise partly read. When an amorphous mass of alum was left for some weeks in water it assumed a pyramidal form, and the lower part of it was embossed by distinct octahedral crystals. Borax exhibited a similar appearance; the lower part was embossed with rhomboidal crystals. Mr. Daniel conceives that in these cases the cohesion of the solid resisted unequally the solvent power of the liquid, and that the upper part of the liquid acted more powerfully than the lower. Hence

the pyramidal form, and hence the appearance of the crystalline texture. These phenomena were observed and described long ago by Le Blanc; but he ascribed the appearance of crystals at the under part of the body to the deposition of crystals from the liquid. But the following experiments of Mr. Daniel render this opinion not so probable. He put bismuth and antimony in very diluted nitric acid; after some days the bismuth exhibited the cubic texture, which is so striking in native bismuth, and the antimony exhibited the appearance of rhomboids. A number of similar experiments with other bodies were related, all tending to prove the accuracy of the conclusion which Mr. Daniel had drawn.

On Thursday, Nov. 23, the remainder of Mr. Daniel's paper was read. He showed that the action of water and different solvents upon crystals was a much more delicate test of their structure than mechanical division. He showed that the supposition, that the integrant molecules of bodies are spheres, will explain the structure of alum crystals; the octahedral crystal, and all the other crystalline forms which it assumes being deducible from the arrangement of such spheres according to the action of gravity, merely by the abstraction or non-formation of certain angles by the removal of a certain number of molecules, while the arrangement of the rest is not altered; but the rhomboidal crystal of carbonate of lime, and the four-sided prism of sulphate of magnesia, cannot be deduced from the arrangement of spheres. Oblong spheroids, however, are capable of producing these forms. No other form of the particles but these two are capable of accounting for the structure of crystals,

LINNEAN SOCIETY.

On Tuesday, Nov. 7, the Society met after the long vacation. A paper by Mr. Johnson was read, giving further information respecting the fossil remains of an animal found at Lynn, in Dorsetshire.

A notice from Mr. Sowerby was read, pointing out the advantages of watering fruit-trees.

Part of a paper by Don Felix Brotero was also read, on the genus passiflora.

On Tuesday, Nov. 21, the remainder of Don Felix Brotero's paper was read.

There was also read an account of a considerable number of specimens of cinchona, by Aylmer Bourke Lambert, Esq. They had been taken in a Spanish ship, and came into the possession of the author of the paper. He was able to distinguish different varieties of known species. Five specimens were not referable to any known species, but appeared new. The yellow bark of the shops is obtained from the cinchona hirsuta of the flora Peruviana. There was also read part of a paper by Dr. Eric Acharius on two new genera of lichens.