attraction? Or is not this phrase composed of incongruous elements? The epithet elective transfers the qualities of sentient beings to unorganized and dead matter; while the word attraction implies the application of that system of forces, which, in its simpler form, constitutes the most perfect of all the physical sciences; and which, modified by the law of distance only, arranges on the one hand the primordial molecules, and on the other extends its empire into the boundless regions of space. The power which unites chemical substances is not absolute and unvaried. In proportion as we approach the limit of saturation of a compound, the mutual adhesion of its ingredients becomes more and more languid. Hence, though the initial attraction, for instance, of a substance A to B be much greater than that of C to B, there is always some intermediate point in the process of the absorption of B, when the force of A, now enfeebled, is counterpoised by the undiminished action of C. It is impossible, therefore, by the help of any re-agents, strictly to resolve a mass into its true elements; the products must always deviate more or less from the just proportions, according to the comparative attractions which are brought into operation. If we add the cohesion of the integrant particles of solids, and consider the various modifications resulting from heat, pressure, and other circumstances, we need not be surprized to view the contrast and discrepancy of different analyses. To refine chemistry in its most essential principles, it would be necessary not only to determine the initial attractions of the common agents, but to investigate the law of the diminution of those forces corresponding to the progress towards saturation. The task is difficult, indeed, and laborious but in the sequel it would perhaps be found that certain analogies, simple in their application, pervade whole classes of objects, and produce all that complication of appearances which at present we despair to unravel.

It was unfortunate, it was rash and illogical, to assume that all the gases are derived from solid bases. The great Lavoisier was evidently misled by the notion of latent heat; an hypothesis originally founded in paralogism, and which has materially impeded the progress of science:-but is there not a radical distinction between vapours and permanent gases? And even granting that various additions of heat are capable of changing any solid successively into the liquid and the aeriform state, what reason is there for maintaining the converse of the proposition? The adherents of phlogiston have been accused, and with reason, of creating an imaginary existence:--but are their opponents altogether exempt from similar reproach? What are oxygene, hydrogene, azote, but étres de science, beings not cogni

zable

zable by the senses, and not demonstrated by their perceived effects? The corresponding gases only are known, and, in all their combinations, these still betray the properties of elastic fluids. Oxyds, for example, possess much less density than the metals themselves; --whence proceeds this distending power? Does not the enlargement of volume decidedly evince a repulsion among the particles of the absorbed air, and which is coerced by the superior attraction of the metal? The same reasoning will apply to a multitude of other facts.

If a mutual attraction subsists among all the different species of air, (as every thing seems to indicate,) the experimenters in that department have committed a grievous oversight, in supposing the bulk of a mixed gas to be equal to the sum of the balks of its components. Hence their analyses will often, from that single cause, be affected with considerable errors. The ordinary pneumatic apparatus, too, however convenient in the infancy of science, is but an aukward contrivance, calculated only to measure gross and palpable quantities:-but to detect the more recondite operations of nature, it is of the utmost consequence to mark the minute alterations of volume, and to exhibit to the senses those delicate transitions which take place in the corpuscular phenomena. Instead of measuring the space occupied by gases, it would be incomparably more accurate to estimate the change of their elasticity by its pressure on a slender column of coloured liquid.

Having stated these preliminary remarks, which, we trust, will not be judged altogether misplaced, we shall now proceed to examine the tracts before us in the order of their occurrence.

I. Experiments on Nitrous Gas, and its combinations with Oxygene. Convinced that eudiometrical experiments, as usually performed, are liable to great uncertainty, and require skilful manipulation, we have always regarded the consequences drawn from them with peculiar hesitation and mistrust. The theory supposes that all the oxygene, contained in the air subjected to trial, unites with a corresponding portion of the nitrous gas to form an acid deposition: but is this acid uniform in its constitution? Does it not assume every possible condition, from the state of red fumes to that of a liquid fixed and limpid? Why presume that the nitrous gas itself is not exposed to a similar variety of composition? Such reflections leave the subject in perplexity; yet it is farther apparent that our suspicions were grounded from M. HUMBOLDT's experiments. These are numerous, and appear to be performed with scrupulous attention: but they are related with such circumstantial detail, and with such frequent repetitions and inci

dental remarks, as to prove tiresome in the perusal. We shall notice only the more prominent results.

The

Authors are not agreed how much nitrous gas is absorbed by one part of the oxygenous: some reckon the proportion at 3, or even 5; Lavoisier states it at 1.8: but M. HUMBOLDT, from a comparison of different analyses, fixes it at 2.55Nitrous gas is not constantly the same; it is modified by the state of concentration of its radical acid, to such degree as to contain a varying excess of azote from 10 to 68 per cent. gas most suitable for chemical experiments is that which is procured from copper-wire, dissolved in dilute nitric acid of between 17 and 20 degrees of Baume's areometer; it contains only 10 or 15 per cent. of surplus azote.-It appears that, when the nitrous and oxygenous gases are mixed in a mercurial apparatus, there is scarcely any sensible precipitation. In ordinary cases, therefore, the contiguous surface of water must perform an important office in assisting the combination." Hence the effect of the concurrence of those two gases depends, in some measure, on the width of the receivers; in narrow tubes, the quantity of absorption which takes place is greatly diminished. If distilled water be shaken with nitrous gas, a portion of the water will be decomposed, and will form, by the play of double affiuities, the nitrat of ammoniac. The solution of the sulphat of iron almost completely absorbs the nitrous gas, detaching the azote, and at the same time composing nitrat of iron and sulphat of ammoniac. The oxygenated muriatic acid, however, detaches still more azote from the nitrous gas. Yet we do not see on what solid grounds. M. HUMBOLDT considers the azote as only adventitious in the nitrous gas, and not constituting an integral part of that The mixture of the nitrous with the varied substance. oxygenous gas affords not such regular results as that with atmospheric air; nor does the artificial compound of 27 parts of oxygenous gas, and 73 of the azotic, manifest on trial the same properties as the air which we breathe. These facts betray the lameness of received principles, and excite suspicions with respect to the legitimacy of some capital analyses. Yet M. HUMBOLDT is not discouraged; and, where the agents are concealed and involved, it is not difficult to imagine a solution of each anomalous appearance. He infers that the quantity of oxygene contained in common air may be ascertained with tolerable accuracy, by dividing the volume absorbed of equak parts of air and nitrous gas from dilute acid, by the number 3.55-but the proportion may be determined with great nicety, by examining the residuum of the mixture, by the help of the sulphat of iron. Nay, with the application likewise of

the

the muriatic acid, he conceives that, by their joint means, we could distinguish to the three hundredth part of the oxygene contained in atmospheric air. We are not so sanguine as the author, though we consider these observations as important, and deserving of attention.

II. On the Causes and Operations of the Solubility of Nitrous Gas in the Solution of the Sulphat of Iron. It was first observed by Dr. Priestley, that nitrous gas is absorbed by the solution of the sulphat of iron. The object of this article, which is the joint production of M. M. HUMBOLDT and VAUQUELIN, is to discover the rationale of that remarkable fact. The general appearances are these: 1. The nitrous gas entirely collapses, leaving only a very minute portion of free azotic gas; 2. the solution changes its green colour into a dirty brown, but without losing any of its transparency, or making any deposit; and 3. its taste, from being sweet and chalybeate, becomes strongly styptic. From the experiments here related, it seems to be demonstrated that the water of the solution is actually decomposed. A curious succession of conspiring affinities is developed: 1. the attraction of the oxygene of the water to the nitrous gas, which composes nitric acid; 2. the attraction of the hydrogene to the free azote, which forms ammoniac; 3. the union of the sulphuric acid with the ammoniac; and 4. the union of the nitric acid with the oxyd of iron.

III. On the Triple Combination of Phosphorus, Azote, and Oxygene, with each other; or on the existence of Oxydated Phosphures of Azote.-This paper was read in the National Institute of France on the 1st Thermidor, 6th year of the Republic. The author mentions several instances of triple combinations in chemistry; and we are convinced that they will afterward be found more numerous than they are generally supposed to be. Phosphorus, which forms an eudiometer so elegant, appears un fortunately to give very uncertain and imperfect results. atmospheric air, instead of discovering 27 parts of oxygene in one hundred, it is capable of absorbing only 15 or 20. It dissolves equally in the azotic or the oxygenous gas, and thus generates a compound with a double base.

With

IV. Description of a Vessel for Absorption, which is particularly applicable to the measuring of Carbonic Gas.-This instrument consists of a very strong glass tube, about a foot long and one third of an inch wide, bent back at the end, and terminating in a ball of an inch and a quarter in diameter. The tube is capped with a screw, and parted in the middle by another screw and socket. For the description and manipulation of the instrument, we must refer to the work itself. We cannot, however,

however, help thinking that it is on the whole a complicated and inelegant contrivance. The ball is filled with liquid caustic ammoniac, or with lime water, and a portion of air is occasionally introduced, which, being exposed to a large surface, soon parts with its carbonic gas. The diminution produced is then measured by the application of a scale divided into the 50th parts of an inch.-The instrument has been termed an anthracometer: but its inventor observes that it would be more' properly denominated an anthroxyometer. What a rage for coining names!

V. On the Carbonic Acid which is diffused in the Atmosphere.There is a considerable diversity in the statement of the quantity of carbonic acid which floats in the air. It was once supposed to amount to the 16th part: but late writers reckon it not to exceed the one-hundredth. M. HUMBOLDT makes the average proportion to be th. The largest quantity that he' ever found was the 3,th, and the smallest the sth. The anthracometer exhibits great fluctuations, but which seem to have no relation to the state of the weather and other obvious causes. Are such observations altogether worthy of reliance?

VI. On the Combination of the Earths with Oxygene, or the Absorption of Oxygene by the Simple Earths, and its influence on the cultivation of the ground.This dissertation contains some original and valuable facts, which may help to throw some light on the theory of vegetation. It appears that clays of every sort have the power of absorbing oxygene from the air, without affecting its other constituents. Fresh mould has likewise the same property in an eminent degree. Hence an easy and beautiful method of procuring the azotic gas in large quantities, since we have only to confine common air over moist earth; and in a few days the oxygene gas is entirely abstracted and imbibed. The simple earths are considerably diversified in their effects: the magnesian, and perhaps silex, manifest no action whatever; nor do the aluminous and calcareous earths, when dry. Alumine, barytes, and lime, when slightly. moistened, all more or less attract oxygene. Heat accelerates the operation.—It seems that water bears an active share in promoting the decomposition. Hence one reason more for its utility in vegetation; and hence the obvious necessity of tillage, or the frequent renewal of the surface of the soil, that the exhausted earth may recover the vivifying principle from the atmosphere.-How finely did the antient mythology depict those truths, which the improvement of science daily reveals and confirms! Our classical readers will recall with delight the philosophical lines of Virgil: