Billeder på siden
PDF
ePub

the muriatic acid, he conceives that, by their joint means, we could distinguish to the three hurdredth 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 Operationis 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 aud 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 ist 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 117fortunately to give very uncertain and imperfect results. With 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.

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 cocket. 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 fillod 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 goth parts of an inch.- The instrument has been termed an anthracometer : but its inventor observes that it would be more properly denominated an anthroa yometer. 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 noth. The largest quantity that he' over found was the ,th, and the smallest the tisth. 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 Eartbs 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 : 14

& Tai

1

[ocr errors]

Tum pater omnipotens fæcundis imbribus ather!
Conjugis in gremium late descendit, et omnes
Magnus alit, magno commixtus corpore, fætus.'

GEORG. II. 3251 After a number of ingenious remarks, M. HUMBOLDT concludes the tract with offering a conjecture on the formation of saltpetre. He supposes that the fat and clayey earths, attracting the oxygene from the atmosphere, set loose the azotic gas; which, finding oxygene in the contiguous stratum, enters into a new order of combination, and forms the nitric acid.

VII. Experiments on the Constitution of the Atmosphere in the Temperate Zone.-These form a very complete set of meteorological observations, made during the space of five months in the winter season at Salzburg. The spot was very favourable, being a garden to the south of the town, in a sheltered valley, encircled on all sides by stupendous mountains. The quantity of oxygene contained in the air varies sensibly at different times. It probably enters into the formation of clouds; it is evolved in the melting of snow; and the atmosphere even shews greater purity when snow falls in large flakes. Rain, dew, and snow, are highly charged with oxygene.

On the tops of mountains, the proper region of clouds, the air is generally more impure than in the plains below. To ascertain the fact, M. Buch made three several journies to the summit of Geisberg, at the height of about 4000 feet; and the air collected there was found by his friend M. HUMBOLDT to contain between one and two per cent. less of oxygene than that of Salzburg. After a thaw has commenced, the atmosphere becomes suddenly purer; owing unquestionably to the oxygenous gas disengaged from the interstices of the snow. In spring, and in the early part of summer, the operation of that cause on the Alpine summits probably more than compensates the ten. dency to deterioration.

VIH. The Evolution of Caloric considered as a Geognostic Phe. nomenon. - This

essay contains miscellaneous observations on the geological theories. It is universally admitted, that the mineral bodies on our globe were originally in a fluid state : they must, therefore, in the prrcess of passing into the solid form, have disengaged a certain quantity of heat. This heat, the author conceives, would modify the subsequent compositions,

IX. Experiments on the Evolution of Light.-M. HUMBOLDT controverts the opinion hitherto received, that plants derive their green colour from the action of light. From repeated observations, he found that plants confined in the dark, with inflammable or mephitic gases, have the same tints as those which grow in the open air; and he concludes that, in every

case,

case, the lively verdure of the vegetable tribes owes its production to a mixture in certain proportions of hydrogene and azote.—The object of the present inquiry, however, is to discover the causes of the phosporic appearance of putrid substances. For that purpose, experiments were made with bits of an old rotten water-pipe, of common Scotch fir. From these trials, which were numerous and delicate, it would seem to be demonstrated that the presence of oxygenous gas is essential to the phænomenon. When the rotten wood, inclosed with irrespirable air, grew languid or ceased to shine, the introduction of oxygene invariably freshened or renewed the glow. The carbonic, the azotic, and the hydrogenous gases were particularly subjected to examination: but it was necessary to prepare them with the nicest attention, and to free them completely from all extraneous matters, since the smallest admixture of oxygene is sufficient to maintain the lucid emission for a very considerable time. Putrid substances, however, shine under water. How shall we account for that fact? Is the faint combustion supported by air disengaged from the water? Yet in boiled water, nay in fresh distilled water, the same appearance is exhibited. M. HUMBOLDT thinks that, notwithstanding the vehement application of fire, there is still a residuum of air adequate to the production of the effect. This explanation, we confess, appears extremely forced. Should we not at least expect a diminution of the glow corresponding to the scantier portion of entangled air? Besides, it is idle to suppose the air to be loosely mingled in the water; it is certainly retained with a very considerable force. - Thegeneral position is opposed also to some able and ingenious experiments of Mr. Thomas Wedgwood, on light and phosphorescent bodies, published in the Philosophical Transactions for the year 1792, of which an extract appeared in Gren's Physical Journal: but M. HUMBOLDT submits, with deference, whether the gases were not prepared by Mr. Wedgwood merely in the ordinary way; and whether certain circumstances in the manipulation might not affect their purity in a slight degree.--Rotten wood loses its phosphorescent quality if immersed in boiling water, or even if exposed to air heated to about the 70th degree of the centigrade scale. That quality is likewise irrecoverably extinguished by dipping the substance in oil, or acidified water.

In the subsequent part of the essay, the author enumerates several decided instances in which light derives its source from other bodies than the oxygenous gas, contrary to the sentiments of many philosophers and chemists.

X. Experiments on the Influence of the Oxygenated Muriatic Acid on the Germination of Plants, and some correlative appear. APP, REY. VOL. XXX.

ances.

Mm

ances. During his residence at Berlin in the winter of 1793, the author discovered that oxygenated muriatic acid accelerates, in a remarkable degree, 'the germination of plants. This Tiotable fact was published in his Flora Fribergensis, and excited much attention in the scientific world. In the years 1794, 5, and 6, his researches were directed to the theory of animalization; and here likewise he found oxygene to constitute the vivifying principle. When a muscular or nervous fibre was quite exhausted by the action of opium, or the hydrogene of alcohol, it would in a few seconds be revived again to the highest pitch of excitability by a few drops of the oxygenated muriatic acid.-With several chemists, particularly in England, these experiments on vegetation have not succeeded; and M. HUMBOLDT was induced to repeat his observations, and to determine the circumstances which are apt to affect the nature of the result. He directs to sow the cress seeds, which are the most convenient for the purpose, not in siliceous earth or wool, but simply in water with the addition of about one-fourth part of the super-oxydated acid. In two or three minutes, the whole surface of the seeds will be covered with innumerable small air bubbles, though more than half an hour would be necessary for the same appearances to take place in common water. In six hours, the first protruding germ becomes visible, which would require the space of thirty-two hours in ordinary cases. In fifteen hours, the radical shoots were often three quarters of an inch long.-- At the botanic garden of Vienna, in 1798, M. M. Jacquin and Schott threw some old torpid seeds into dilute oxygenated muriatic acid. The experiment fully succeeded: The Guilandina Bonduc, the Cytisus Cajan, the Dcdonea Angustifolia, the Mimosa Scandens, and several new species of the Ipoman, germinated. Some of those rare plants are now six or eight inches high. Similar experiments have been made at Dresden and Salzburg.

XI. Pocket or Sirik Barometer. -Such is the strange title given to a machine which, when carried, must be slung over the shoulder like a musket. The object of this construction is, that it may be taken occasionally to pieces and examined. In fact, the tube, the bason, and the scale, are all separate, and must be put together as often as an observation is made. This seems to be reverting to the primitive state of the mountain barometer, as it was used by Pascal in measuring the height of the Puy de Dome. We need say nothing more.

XII. Letter to Garnerin on the Analysis of the Atmospheric Air, which was collected by means of an Air Balloon at the Height of 669 Toises. - It was found to contain about one hundredth part of carbonic gas, and 259 thousand parts of oxygenous gas,

« ForrigeFortsæt »