thing happens to the first class of bodies when they are sufficiently heated to let go their hydrogen. These experiments presented some curious appearances. A mixture of starch and iodine, when triturated, assumes a red, blue, or black colour, according as the iodine is more abundant, &c.

But our associate Gay-Lussac is the person who has made the most extensive and careful set of experiments on iodine. His paper has been printed in the Annales de Chimie. He examines iodine itself, its combinations, and those of its two acids with different bodies. These, according to the established rules of nomenclature, are denominated iodurets, iodates, and hydriodates. He treats likewise of chlorine, and makes some new remarks on its combinations, all of which had not been correctly appreciated. Then considering prussic acid as essentially formed of azote, hydrogen, and carbon, he concludes that azote ought likewise to be added to the list of substances capable of producing acids without oxygen. This leads him to consider acidity and alkalinity as properties belonging to certain bodies and certain combinations, without any necessary relation to their composition, as far as can be discovered, and which of consequence makes it approach to the ideas of Winterl and some German chemists. This memoir is full of delicate investigations and ingenious hints, of which it is not possible to give an account, but which will not fail to give a new spring to the most profound and most important department of chemistry.

Our respectable associate M. Sage, who, notwithstanding his age and infirmities, always takes a lively interest in new chemical facts, has likewise made experiments on iodine, and on kelp, from which it is obtained. He has observed the alteration produced by iodine in the silver vessels in which it is heated. Kelp furnished him, by naked distillation, products analogous to those of animals; and by macerating them in weak nitric acid, he obtained a cartilaginous net, similar to that left by bones and by madrepores when deprived of their earthy parts. M. Sage concludes, from these two facts, that the fuci are polypi.

The same chemist has presented likewise a notice on the advantages of reducing galena by the fire. He affirms that by this method much more lead is obtained than by the ordinary way.

M. Theodore de Saussure, correspondent, who in 1807 had read to the Class a memoir on the composition of alcohol and of sulphuric acid, of which we gave an account at the time, and from which it resulted that ether contains more carbon and hydrogen than alcohol, has last year resumed this important object of investigation, and making use of methods at once more simple and more rigorous, has obtained a more exact result. By passing these two liquids through a red-hot porcelain tube, he converted them into water and a gas, the analysis of which presented no difficulty. By this method be ascertained that alcohol and ether contain each an identical proportion of carbon and hydrogen, and in the same ratio that they

are in olefiant gas, but combined with different proportions of water reduced to its elements.

In alcohol the elements of water form a third of the whole, and in ether they form the fifth part; so that the action of sulphuric acid upon alcohol to produce ether seems to consist only in depriving it of a portion of its water; and the same acid, when applied in greater quantity, produces olefiant gas, by removing the whole of the water.

The analytical results of M. de Saussure agree with those obtained by the late Count Rumford, respecting the quantity of heat produced by combustion of alcohol and ether.

One of the great difficulties in the analysis of organic bodies consists in this, that chemistry possesses but a small number of reactives capable of separating the immediate principles without destroying them. M. Chevreul, Assistant Chemist in the Museum of Natural History, has endeavoured to render them more useful, by employing very different degrees of heat, and thus varying their solvent power.

For this purpose he has contrived a machine, which he calls a distillatory digester, consisting in a Papin's digester, shut by a valve attached to a spring. The force of this spring, which is altered at pleasure, determines the degree of heat which the liquid must receive in order to escape. The produce of each degree is successively collected by means of a tube passing into a receiver. The solid matter under examination is retained in the digester by means of a diaphragm, by which it may be pressed, and all the remaining liquid forced out of it.

M. Chevreul has made experiments on cork by this method. He subjected it 20 times to the action of water, and 50 times to that of alcohol. Having thus separated various substances, there remained a cellular body, which he calls suberin, and which, when treated by nitric acid, is converted into suberic acid. Among the substances thus extracted from cork, there is one which he considers as new, and which he calls cerin, because it possesses several of the properties of wax.

The same chemist has applied his method to amber, and ascertained that succinic acid exists in it in a perfect state.

He has likewise continued his researches on saponification, of which we gave an analysis last year. By comparing fat in its natural state with that which has been saponified, he has concluded that the new properties of the last do not proceed from the separation or addition of any constituent, but from a new mode of combination, occasioned by the action of the alkali, which gives to fat an analogy with the acids independent of all oxygenation.

M. Pelletier, the son of our deceased associate, has examined the colouring matters from sandal wood and alcanette (anchusa tinctoria), hitherto considered as mere resins. The first, besides possessing most of the properties of resins, is soluble in acetic acid,

even when very weak, and then acts upon gelatine like astringent bodies, and forms oxalic acid when acted on by nitric acid. It possesses, besides, some other characters, which seem to raise it to the rank of a peculiar vegetable principle. The colouring matter of alcanette dissolves in ether, alcohol, and expressed oils. When treated with nitric acid, it gives oxalic acid and bitter principle. Alkalies and water make it undergo various changes of colour. These united properties, in the opinion of M. Pelletier, entitle it likewise to be considered as a peculiar vegetable principle.

We have seen formerly that crude platina, as extracted from the mine, contains several foreign substances, and among others, four peculiar metals, which have been lately described. Last year we described the methods employed by M. Vauquelin to separate palladium and rhodium (two of these metals form a solution of platinum in nitro-muriatic acid); and to obtain them in a state of purity. We mentioned, likewise, that M. Laugier having perceived that this solution contains a notable quantity of a third metal, remarkable for its volatility, on which account it received the name of osmium, had pointed out a method of collecting it.

A black powder, which does not dissolve in nitro-muriatic acid, remained to be examined. It forms the residuum after the solution of crude platinum. It is composed chiefly of osmium, and of a fourth metal, to which, on account of the various and lively colours of its solution, the name of iridium has been given.

These two metals are united in that powder with chromium, iron, titanium, silica, and even with a little alumina. The difficulty was to separate them completely from this mixture, and to obtain them in a state of purity.

Vauquelin has succeeded in this, but by laborious and complicated processes.

Simple washing divides this powder into two parts; one, finer and more brilliant, contains more iridium and osmium, and scarcely any chromium; the other, browner and coarser, contains less of the first two metals and more of the others. As this last portion is the most difficult to analyze, we shall confine ourselves to it.

M. Vauquelin triturates it in the first place with twice its weight of nitrate of potash. The oxygen of the acid oxidates the iridium and osmium, which combine with the disengaged potash. The application of heat disengages a great part of the acid and the osmium, which are received in lime-water. The residue, diluted and saturated with nitric acid, gives a precipitate of iridium, titanium, iron, alumina, and a little oxide of chromium, and there remains a liquid composed of potash united to chromic acid and to osmium. This last metal is separated by adding nitric acid and distilling, receiving the osmium in a flask surrounded by ice. A little muriatic acid is poured into the water containing the osmium. A plate of zinc is then introduced, which precipitates the osmium. To obtain it quite pure it is washed with water acidulated with a little sulphuric acid.

The chromium is next to be separated. For this purpose the liquid is evaporated, the residue dissolved in water, and filtered, to separate the silica that may be present. Pronitrate of mercury is then poured in, which occasions a precipitate of chromate of mercury, which, being dried and heated, gives the green oxide of chromium. There remains for examination the first precipitate of iridium, titanium, iron, chromium, and alumina. There is likewise a little osmium, which is removed by digesting in muriatic acid, distilling, and precipitating by zine as before. If there remain portions undissolved, they must be triturated with nitre, as at first; and we observe that the oftener this operation is repeated the more blue do the muriatic acid solutions become, because they contain less and less iron and titanium, which, as more easily dissolved, are first acted upon by the acid, and leave behind them a greater proportion of iridium.

Now iridium has this property: when in that state of oxidation that it forms red solutions in acids, it is only precipitated by salammoniac, and that in the state of a triple salt. It is therefore brought to this state by boiling its muriatic solution with nitric acid. The liquid is neutralized by ammonia. By boiling, the iron and titanium are thrown down. The iridium is then precipitated by salammoniac; and the triple salt obtained, when exposed to a red heat, leaves iridium in a state of purity.

This metal, so difficult to separate from the singular alloy which concealed it from all eyes, possesses remarkable properties. Its colour and lustre are very similar to those of platinum. It is more difficultly fusible. It is insoluble in the simple acids, difficultly soluble in nitro-muriatic acid; but potash and nitre oxidize it, and combine with it into black powder, which gives a blue-coloured solution. With boiling nitro-muriatic acid, it forms a red solution. Its blue solutions themselves become red when boiled; but both the blue and the red solutions are discoloured by sulphate of iron, sulphureted hydrogen, iron, zine, and tin. Oxymuriatic acid causes them to resume their colour. It is iridium which gives a red colour to the last precipitates of the triple salt of platinum, while the first precipitates, into which it does not enter, are yellow.

Its

The properties of osmium are not so easily determined, in consequence of the ease with which it is oxidated and volatilized. oxide is white, and very caustic. It exhales an unsupportable odour. It is flexible and fusible, like wax; and as soon as it touches an animal matter, it blackens it. Its solution in water becomes blue by nutgalls, &c.

M. Mongez, member of the Class of Ancient Literature, has read a memoir on the bronze of the ancients, in which he shows, from experiments made by M. Darcet, that it is not by immersion in cold water that bronze becomes hard, as is the case with steel; but that it acquires its hardness by being heated red-hot, and then allowed to cool slowly in the air. M. Darcet has taken advantage of this property to make symbals, instruments hitherto made only in

Turkey, and, it is pretended, by a single workman in Constantinople, who possesses the secret.

The falls of stones from the atmosphere, since the reality of the phenomenon has been constated, are observed so often, that by and by the most astonishing thing will be the long incredulity entertained respecting them. A remarkable fall took place this year in the department of the Lot-et-Garonne. It happened on the 5th of September, and, as usual, in fine weather, with a strong explosion and a whitish cloud. The number of stones was considerable; one of them was said to weigh 18 pounds. They were scattered over a surface of about a league radius. Their external characters and composition are absolutely the same as in other stones of the same origin, only their fracture has tints a little more marbled than common. Excellent reports by two good observers at Agen, MM. de Saint-Amans and Lamouroux, have made us fully acquainted with the details of the phenomenon.

M. le Comte Berthollet has presented to the Class, on the part of Mr. Tennant, one of the stones that fell last year in Ireland, and which resemble all the others, excepting that they contain a little more iron.

It is known, and we have had repeated occasions to mention it, that the stone called arragonite furnished the strongest objection that could be produced against the employment of crystallization in the classification of minerals; because chemists had found no difference between its composition and that of calcareous spar, though the crystalline forms be essentially distinct. This objection is now removed. M. Stromeyer, Professor of Chemistry at Gottingen, has discovered the constant presence of three per cent. of strontian in arragonite, while none exists in calcareous spar. M. Laugier, Professor in the Museum of Natural History, has repeated this analysis, and obtained the same result. It remains to be explained how the addition of so small a quantity of a constituent can change so completely the form of the primitive molecule of a mineral.

(To be continued.)

ARTICLE XII.

SCIENTIFIC INTELLIGENCE; AND NOTICES OF SUBJECTS
CONNECTED WITH SCIENCE.

The river Missouri, which was navigated in 1805 and 1806 by Captains Louis and Clarke from its junction with the Mississippi to its source, runs a course east and south of above 3000 miles. It rises in a very elevated group of mountains situated between northlatitude 44° and 45°, and about west longitude 112°. The height