memoir on hygrometry, containing the immediate consequences of these experiments; but these works not having, in his opinion, acquired that precision and order which he is accustomed to give to all that he publishes, the author has thought proper to defer the printing of them.

M. Ďulong, Professor at Alfort, has presented some experiments on oxalic acid, which, though not constituting a complete work, open interesting views for the science. When this acid is saturated with barytes, strontian, or lime, we obtain always salts, which represent the acid employed even when they have been exposed to a heat higher than that of boiling water. But with oxide of lead, or of zinc, we always lose 20 per cent. of the acid by drying. When these metallic salts are afterwards strongly heated, no water makes its appearance; but we obtain carbonic acid and carbonic oxide, and there remains behind the oxides of the metals employed, of which that of lead possesses particular properties. The oxalates of copper, silver, and mercury, on the contrary, always give out water when decomposed, how dry soever they are previously made. Carbonic acid is likewise given out, and the base remains in the metallic state. The oxalate of silver detonates, and we know already that it detonates when struck, as well as the oxalates of mercury.

As to the oxalates of barytes, strontian, and lime, they give, when decomposed by heat, empyreumatic oil, water, carbonic oxide, carbureted hydrogen, carbonic acid, and there remains a mixture of subcarbonate and charcoal.

These phenomena may be explained two ways. Oxalic acid is either composed entirely of carbon and oxygen, in proportions intermediate between those of carbonic acid and carbonic oxide; but it contains water, which certain oxalates, as those of lead and zinc, lose when dried; while others retain it. Or it is a compound of carbonic acid and hydrogen. This last constituent, with the oxygen of the oxide, will form water, which these first oxalates likewise allow to escape, and nothing remains but carbonic acid and the metal, a combination quite new in chemistry: for it is regarded as a general principle, that metals are capable of uniting with acids only after being oxydised. M. Dulong, who is inclined to this last explanation, conceives of course, that the dried oxalates of lead and zinc are not real oxalates, and he proposes to give to them, as well as to similar compounds that may be discovered, the name of carbonides. The oxalates which do not give water by drying, contain the oxalic acid entire; and as from its composition it will be named hereafter hydro-carbonic, the salts will take the the name of hydro-carbonates.

M. Dulong is led by analogy to very general conclusions, by which he reduces under the same laws, not only the ordinary acids, but likewise the hydracids. But we shall give a more detailed account of his opinions, when he sends up the memoir in which he intends to consign them.

The chemical action of solar light on bodies is worthy of all the

attention of philosophers, from its influence on most of the phenomena of living nature, yet it has hitherto been but little examined. M. Vogel has just added some experiments to those which we formerly possessed. Ammonia and phosphorus, which do not act on each other in the dark, when exposed to the solar light disengage phosphoreted hydrogen gas, and deposit a black powder composed of phosphorus and ammonia intimately united. Nearly the same thing takes place with phosphorus and potash. The action of the different rays is not always similar; the red rays produce no effect on the solution of corrosive sublimate in ether, while the blue and complete light produce a mutual decomposition. The metallic permuriates are brought in the same way to the state of protomuriates.

We have said a few words in our two last reports on the researches of M. Chevreul, assistant naturalist to the Museum of Natural History, concerning soap and saponification. This skilful experimenter has ascertained that the action of potash on tallow produces new modes of combination, from which result substances which did not exist before perfectly formed, and two of which, margarine and a species of fluid oil, acquire all the properties of acids. The author, pursuing his experiments, has ascertained that the same effects are produced by soda, the alkaline earths, and different metallic oxides, and that the resulting substances are in the same proportion, whatever agent we have employed. Magnesia and alumina on the contrary merely contract a certain union with tallow, without separating its elements into two distinct bodies. The quantity of alkali necessary to convert a given portion of tallow into soap is exactly that which saturates the margarine and oil which the tallow produces. Our laborious chemist has terminated his memoirs on this subject, by giving the capacity of saturation of margarine and fluid tallow, and by describing the properties of several new soapy combinations which he produced by double decompositions, by mixing a hot solution of soap, of fluid tallow, and potash, with different earthy and metallic salts. Thus he has rendered the soaps, the study of which has been hitherto neglected, almost as well known as the salts with which chemists have been the most occupied.

The late M. Fourcroy made known, under the name of adipocire, a substance separated by means of acids from the fatty matter into which animal bodies buried in the earth are converted. And he considered it as identical with the crystalline matter in human biliary calculi, and with the spermaceti found abundantly in certain cavities of the head of the cachalot.

M. Chevreul, led by his experiments to examine these substances, has found that the crystalline matter of biliary calculi does not form soap, while spermaceti furnishes it as easily as tallow; but producing a somewhat different alteration in other proportions and with particular properties. The fatty matter of dead bodies is much more compound than Fourcroy had supposed, containing dif ferent fatty bodies combined with ammonia, potash, and lime. It is a fatty matter that has already experienced the action of alkalies. Every person must have observed a resinous excretion of a yel

lowish-orange colour, which exudes from cracks in the bark of beech faggots exposed to moisture. It has the shape of ribbons, twisted like vermicelli. M. Bidault de Villiers has made some chemical experiments on this matter. One portion of it dissolves in water, another in alcohol, and the residue possesses some of the properties of gluten. Nitric acid converts it into oxalic acid, into a yellow bitter principle, which is very abundant, and into a fatty matter; but produces no saclactic acid. When heated it gives abundance of carbonate of ammonia, and a fetid oil; so that the Commissioners of the Class were led to consider it as approaching very closely to an animal substance. It would be interesting to inquire into the cause of its production.

One of the periods in which chemistry has shown itself most brilliant and most useful, was certainly that in which France, separated for 20 years from countries whose productions had been considered for so long a period as real necessaries, was obliged to supply them by the products of its own soil. The known arts have been perfected and new ones created. We have seen in succession soda extracted from common salt; alum' and copperas formed by uniting their ingredients; colours considered as fugitive rendered permanent; indigo from woad supplying that from the indigofera; madder supplying the place of cochineal; and sugar from beet employed as a substitute for that from the sugar cane.

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This last article, the most important of all, is far from having lost its interest even at present. Many of the manufactories, indeed, have fallen; but those which were properly conducted still subsist and prosper; and according to M. le Comte Chaptal, their product will always be able to rival the sugar of the colonies. This skilful chemist gives an unanswerable proof of his assertion by continuing to manufacture with profit. It is true that in all the details of the culture, harvest, and preparation, and likewise in the employment of the different waste matters, he has applied all the lights of science and experience, so as never to throw away what can be of any service, and to apply to other uses what he is obliged to reject. He has described his processes in a manner sufficiently clear to be understood by all the manufacturers, and we have reason to hope that his work will assist in preserving to France a precious manufacture, which a thousand events may again render necessary to the country.

The third volume of the Elementary Chemistry of Thenard has been published. This skilful Professor describes in it with great minuteness, and according to the most recent discoveries, for many of which the science is indebted to himself, the immediate principles of organized bodies, the different products of their decompositions, and their uses in the arts. The fourth, which is in the press, will terminate the work.

ARTICLE VIII.

SCIENTIFIC INTELLIGENCE; AND NOTICES OF SUBJECTS
CONNECTED WITH SCIENCE.

I. Lectures.

Mr. Clarke will commence his next Course of Lectures on Midwifery, and the Diseases of Women and Children, on Monday, March 18. The lectures are read every morning, from a quarter past ten to a quarter past eleven, for the convenience of students attending the hospitals, at No. 10, Saville-row.

II. On taking Specific Gravities, and on the Cause of the Rupture of Leaden Pipes from Frost: in an Extract of a Letter from Dr. Redman Coxe, Professor of Chemistry, Philadelphia.

It occurs to me, before I close my letter, to mention what I consider as a source of error in determining the specific gravities of bodies; this is the employment of water as a standard at any other temperature than that at which this fluid is of a mean density, viz. at about 40°. If both above and below that point this fluid expands both by an increasing and diminished temperature, ought we not to fix upon that degree invariably for the purpose? for as we judge by comparative bulks of matter, a little variation may induce considerable difference of result. Another circumstance arising from this anomaly in water expanding by cold below 40° is, that this is the chief cause of leaden pipes bursting, and not from the mere sudden expansion in its conversion into ice. My reason for believing this to be the case is, that we never see the leaden tube burst throughout the whole length, as should be the case if the solidification of the water was the cause; for as this is uniform throughout, so ought the effect to be: but it is chiefly in a small point, arising, as may be seen, from the gradual diminution of thickness in that part of the pipe, until becoming as thin as paper, it can no longer sustain the pressure of the fluid, and therefore yields. Hence only a few small openings are perceptible, not bigger than pins' heads, which takes off the pressure by giving vent to the water. If this is the case, how can it be guarded against, excepting by increasing the thickness of the tube? Now as the water goes into the pipe in a fluid state, it can scarcely become colder below the earth, removed as it is from the influence of the frost. This is a circumstance worthy of consideration in large cities where leaden pipes are employed for the distribution of water. Did you ever hear of rats gnawing the leaden pipes to get to the water within? I have a large specimen of this kind.

III. Chyle.

Dr. Marcet has published a set of comparative experiments on the chyle from vegetable and animal food, in the sixth volume of

the Medico-Chirurgical Transactions. The chyle was collected from the thoracic duct of dogs within three hours after they had been fed. The following were the results obtained :

1. Chyle from Vegetable Food.-It appeared a short time after being collected, in the form of a semi-transparent, inodorous, colourless fluid, having a very slight milky hue, like whey diluted with water. It contained a coagulum, which was semi-transparent, and resembled the white of an egg, but had a pink hue. The weight of the fluid part to that of the coagulum was 100 to 48; but the coagulum being put into a phial by itself, a quantity of fluid similar to the serous portion speedily oozed out, and left only a very small clot. This residue began to putrefy at the end of a week. Potash caused a slight ammoniacal smell to exhale from the fluid which issued from the clot; and the mineral acids, especially the nitric, precipitated abundance of white flakes, which were partly redissolved by dilution and heat.

The serous portion had the specific gravity 1.0215 or 1.022, It did not putrefy in ten days, but acquired a smell similar to that of sour cream. Heat rendered it somewhat turbid and milky. The mineral acids threw down abundance of albumen: 100 parts of it being evaporated to dryness, left 4.8 parts of a yellow and very deliquescent solid residuum. Some other portions yielded more solid matter. The greatest quantity was 9.5 per cent.

cream.

2. Chyle from Animal Food. It was white and ópake, like The coagulum was white and opake, and had a more distinct pink hue. The proportion of the fluid to the coagulated por tion was 100 to 46'5. This coagulum, like the preceding, gradually gave out a serous fluid, till only a very small quantity of matter remained. This residue, somewhat similar to thick pus, became putrid in three days.

The serum, on standing, formed an opake creamy substance on its surface. Heat rendered it more turbid than the preceding serum. It contained abundance of albumen. The quantity of solid matter contained in it was seven per cent.

These liquids, when distilled, gave out moisture, carbonate of ammonia, and a heavy fixed oil. Vegetable serum left three per cent. of charcoal; and animal serum, one per cent. The presence of iron was recognized in the residuum, and the same proportion of salts (about nine in the 1,000 parts) that exist in animal fluids in general.

IV. Chyme.

Dr. Marcet likewise examined chyme from the stomach of a turkey. It was a homogeneous, brownish, opake pulp, having the smell which is peculiar to poultry. It was neither acid nor alkaline, and became putrid in 12 days. When evaporated to dryness, it left nearly one-fifth of its weight of solid matter. It contained albumen. When burnt, it left 12 parts in the 1000 of charcoal. This residuum contained iron, lime, and an alkaline muriate.