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Alexander von Humboldt, Louis Joseph Gay-Lussac: „Experiments on the Eudiometrical Means, and on the Proportion of the Constituent Principles of the Atmosphere“, in: ders., Sämtliche Schriften digital, herausgegeben von Oliver Lubrich und Thomas Nehrlich, Universität Bern 2021. URL: <https://humboldt.unibe.ch/text/1805-Experiences_sur_les-4-neu> [abgerufen am 23.07.2024].

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Titel Experiments on the Eudiometrical Means, and on the Proportion of the Constituent Principles of the Atmosphere
Jahr 1806
Ort London
Nachweis
in: The Repertory of Arts, Manufactures, and Agriculture 8:45 (Februar 1806), S. 231–239; 8:46 (März 1806), S. 303–318; 8:47 (April 1806), S. 365–381; 8:48 (Mai 1806), S. 449–461.
Beteiligte Louis Joseph Gay-Lussac
Sprache Englisch
Typografischer Befund Antiqua; Auszeichnung: Kursivierung; Fußnoten mit Asterisken; Schmuck: Initialen, Kapitälchen; Tabellensatz.
Identifikation
Textnummer Druckausgabe: II.32
Dateiname: 1805-Experiences_sur_les-4-neu
Statistiken
Seitenanzahl: 55
Zeichenanzahl: 93388

Weitere Fassungen
Expériences sur les moyens eudiométriques, et sur la proportion des principes constituans de l’atmosphère (Paris, 1805, Französisch)
Versuche über die eudiometrischen Mittel und das Verhältniß der Bestandtheile der Atmosphäre (Berlin, 1805, Deutsch)
Versuche über die eudiometrischen Mittel, und über das Verhältniss der Bestandtheile der Atmosphäre. Vorgelesen in der ersten Klasse des National-Instituts am 21sten Jan. 1805 Zweiter Teil: Ueber die Natur der Luft, welche man aus dem Wasser erhält, und über die Wirkung des Wassers auf reine und auf vermischte Gastarten (Halle, 1805, Deutsch)
Experiments on the Eudiometrical Means, and on the Proportion of the Constituent Principles of the Atmosphere (London, 1806, Englisch)
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Experiments on the Eudiometrical Means, and on the Pro-portion of the Constituent Principles of the Atmosphere.By Messrs. Humboldt and Gay-Lussac. From the Journal de Physique.

IF philosophers and chemists are at present agreed re-specting the nature of the constituent principles of theatmosphere, they are not yet so with regard to theirabsolute quantity. Since Scheele and Lavoisier, whohad found twenty-seven hundredths of oxygene in the air,numerous experiments, for which we are indebted to |232| Messrs. Cavendish, Marti, Berthollet, Fourcroy, andDery, have greatly modified this proportion, by fixingit at between twenty and twenty-three hundredths. Ne-vertheless it must be admitted that these proportions arestill far remote from that degree of accuracy which thepresent state of Science allows of; or, if these limits arewell established, it must be concluded that the atmosphereexperiences considerable oscillations in its composition.Although with respect to most chemical phenomena, it isnot necessary that we should have an accurate knowledgeof the absolute quantity of its principles, this knowledgeis not less interesting in itself, than important with re-gard to the history of our globe. If all the facts of geo-logy tend to prove that the earth is no more what it hasformerly been; that the highest mountains have beencovered with water, and that the Arctic regions havenourished animals which at present are to be found onlybetween the tropics, these very changes prove of whatgreat utility it would be to future ages actually to ascer-tain the physical state of the globe at the present day;and even though the grand catastrophes which it has al-ready experienced should never more be reiterated, it ispossible that it may undergo gradual modifications whichman would not be able of himself to appreciate, unlesshe found incontestible documents in the annals of science.It would therefore be of the highest importance to fix inan authentic manner the grand phenomena of nature,which are to be supposed subject to variation; such asthe intensity of the magnetic forces, the elevation of thebarometer at the level of the sea, that of the sea itself,the medium temperature of every climate, and the pro-portion of the constituent principles of the atmosphere.We have directed our attention to the latter question, andalthough we have not yet solved it in a manner entirely |233| satisfactory to ourselves, we venture to give an accountof the commencement of the investigation which we haveundertaken upon this subject, and the researches to whichit has led us. But the eudiometrical means which must serve to de-termine the proportions of the constituent principles ofthe air are not all susceptible of equal precision, and somedistinguished chemists give the preference to a meanswhich is rejected by others. It therefore was indispensa-bly necessary that we should put to the trial the knowneudiometrical methods, in order that we might be ena-bled properly to appreciate their value; for we are wellconvinced that accuracy in experiments depends less uponthe faithful observation of the divisions of an instrument,than upon the accuracy of the method itself. Althoughthe nitrous gas appears indeed at first to be the most un-certain eudiometric means that can be chosen, we haveconvinced ourselves that by combining its action withthat of the sulphate of iron, or of the oxygenated muria-tic acid and of potash, it is capable of indicating withgreat precision the quantity of oxygene contained in theair. All the eudiometrical means would give the sameresults, if we were equally acquainted with them all, andit is only because it is very difficult to make all the cor-rections they allow of, that we naturally give the prefer-ence to such as present less occasion for them, althoughthey are not always the most simple in their use. Weshall therefore first give an account of the eudiometricalresearches with which we have occupied ourselves, andthen apply them to the analysis of the atmospheric airand of that obtained from water under different circum-stances, or placed in contact with it. We find it neces-sary again to repeat that we shall not treat the questionwhich we have proposed to ourselves in so extensive a |234| manner as it merits. Compelled to break off our re-searches before we were able to bring them to their ter-mination, our purpose is only to give an account of theirprincipal results. During nearly two months since thetime that we commenced them in one of the laboratoriesof the Polytechnic-school at Paris, we pursued them, inspite of the coldness of the weather, which is very dis-agreeable in researches of this kind, with so much thegreater assiduity, as M. Humboldt found a peculiar in-terest in them. In the year 6, he had presented to theInstitute two memoirs on the analysis of the air, whichcontain a great number of experiments, which he nowconsiders (it is he himself that avows it) not only as veryinaccurate, but also as very justly controverted by Mr. Davy, and by a chemist with whose particular friendshipwe are both honoured, namely, M. Berthollet. Zealousfor the advancement of science, M. Humboldt, when hecommenced his researches, wished to substitute in theplace of those investigations of his early youth, othersfounded upon more solid foundations, and as he desiredto have me for his associate in them; I ought to considermyself the more highly honoured by his proposition fromour having been, since his return from the tropics, linkedtogether in the closest bonds of friendship.

Observations on several of the Eudiometric Means.

It is not our intention in this memoir to record all theresearches which we have undertaken upon different eu-diometric means: most of them are still in too imperfecta state; but having occupied ourselves more particularlywith the alkaline sulphurets, and especially with hydro-gene gas, we shall here exhibit the result of our obser-vations on these two eudiometrical means. |235| Although the alkaline sulphurets have in general a suf-ficiently-constant action for the analysis of the air, whichhas caused them to be justly preferred to the other eudio-metrical means, they nevertheless present some sources oferror, which it is indispensibly necessary we should bewell acquainted with, in order to justify us in placing anentire confidence in their results. It has long been be-lieved that they have no action upon the azote; and al-though M. Marti announced, as early as in the year 1790,that they absorb this gas, no farther attention has sincebeen paid to this property. It is true M. Marti at thesame time announced, that by saturating them with azotewe might employ them to advantage for the analysis ofthe air, and constantly obtain for the oxygene a propor-tion comprehended between 0.21 and 0.23. On the otherhand, this chemist not having indicated the details of hisexperiment with sufficient precision, M. Berthollet, whorepeated it after him under different circumstances, an-nounced in his Chemical Statics, that he had not foundthe alkaline sulphurets to possess the property of absorb-ing azote, whereby he gave new sanction to their em-ployment for the analysis of the air. When we began toemploy this means we placed great confidence in it, andhad nothing to object to it but the great length of timewhich it requires, and which had long rendered it a de-sirable object that, notwithstanding its accuracy, someother might be substituted in its place that were not at-tended with the same inconveniences; but we soon dis-covered that it did not always act in an uniform manner,and herein we were favoured by accident. Having placed 100 parts of atmospheric air in contactwith a solution of sulphuret of potash, made with hotwater, in three vessels of unequal capacities, we observedat the end of eight days that the air had lost twenty-threeparts of its volume in one of the vessels, and 23,6 26,0 |236| in the two others. This great inequality gave us at firstmuch surprise; but having remarked that the absorptionhad been most considerable in the largest flask, we sus-pected that azote had been absorbed, and, in order thebetter to confirm our suspicion, we repeated the sameexperiment, employing two vessels more unequal in ca-pacity, but otherwise placed in the same circumstances.At the end of ten days we found that in the small flaskthe absorption had been only 22,5 parts, whilst in thelarge one it was 30,6. But the most decisive experi-ment which we made on this subject, was the placing ofa solution of sulphuret of potash, which had been heatedto ebullition, in contact with azote in unequal vessels,when it was discovered that the absorption was propor-tionate to their capacities. It would therefore be possi-ble to cause a determinate quantity of atmospheric air tobe absorbed by a solution of alkaline sulphuret, and tomake it be considered as pure oxygene, if it were sup-posed that the whole diminution of volume were owingto the oxygene gas. But if, instead of employing asolution of sulphuret made with hot water, we em-ploy one made with cold, as M. Berthollet has alwaysdone, the solution of the azote takes place no longer, atleast not in a perceptible manner, and the results of theanalysis of the air made by this means become then muchmore susceptible of comparison. This variable action ofthe alkaline sulphurets, dissolved at different tempera-tures, requires to be farther elucidated, which we areabout to do by citing phenomena of an analogous butmore comprehensible nature. As water always holds in solution a certain quantity ofair in which the proportion of oxygene is more consider-able than it is in the atmospheric air, it happens thatwhen we heat it, or dissolve a salt in it, a part of its air isdisengaged from it whilst another is retained, which may |237| be separated from it by a more intense heat. If, there-fore, we place this water, which has been deprived of itsair by the last-mentioned means in contact with atmos-pheric air, it will absorb, in returning to its originaltemperature, a quantity equal to that which it has lost;and if we were not aware of this absorption, but judgedupon appearances, we should suppose that the wateralone, or charged with salt, had made the analysis of theair. Thus M. Hetter has very recently announced thata solution of muriate of soda absorbed all the oxygene ofthe air, though on repeating his experiment with ahighly-charged solution of the same salt, but made withcold water, we did not find the slightest difference be-tween the ordinary atmospheric air and that which hadbeen in contact with the solation of muriate of soda fora month and a half. The very same thing happens with a sulphuret as witha salt. At the moment of its solution in water, a portionof air is expelled, and an equilibrium of saturation isestablished between the water, the sulphuret, and the airwhich it holds in solution, so that if the circumstancesare not changed, there is now no reason why it shouldabsorb a fresh quantity of air; but if we heat the solu-tion, there is disengaged from it a part of the gas whichit contained, and, in returning to its original tempera-ture, it is necessary that it absorb what it had lost, in or-der that its equilibrium may be re-established *. We
* The absorption of which we mean to speak in this place is inde-pendent of that of oxygene by the sulphuret, which is thereby con-verted into sulphate. But as the sulphuret absorbs the oxygenewhich the water holds in solution, it will very probably happen thatthe water will be able to absorb a larger quantity of azote; so that ifwe employed a solution made with cold water, and very recently pre-pared, there would be a still greater diminution of volume than thatwhich is owing to the absorption of the oxygene. We say very proba-bly; for we have not yet made the experiment.
|238| think, therefore, that the difference between the resultsof Messrs. Marti and Berthollet may be explained by thedifference of the circumstances under which they ope-rated; but it appears to us, that M. Marti believedthat it was the nature of the sulphuret to absorb azote,whereas it does not absorb it all, but rather prevents thewater with which it has been boiled from absorbing asmuch as it would do without it.
Thus if we take care to dissolve the sulphurets in coldwater, and leave them for some time in contact with azoteor with air, we may employ them with advantage for theanalysis of the atmosphere. We shall however observe,that as they are attended with the inconvenience of re-quiring a great length of time before their action is com-pleted, we are obliged to have recourse to the correc-tions of the thermometer and barometer, which often arevery uncertain. The best way of remedying this incon-venience is undoubtedly to follow the method of Messrs. Berthollet and Marti, which consists in placing, for com-parison, upon water a determinate quantity of air, inorder to judge, from its variations of volume, of that ofthe air which we analyze; but this method has not ap-peared to us to be attended in practice with all the ad-vantage which it seems to promise. We must still remark with regard to all the eudiome-trical means, where the absorbing substance is solid orliquid, that if we commit an error, either in observingthe divisions of the instrument, or in the appreciation ofthe uncertainties of the method, this error necessarilyfalls altogether upon the quantity of oxygene; and sincewith all possible exactness we cannot answer for itsamounting to much less than a hundredth part, it wouldfollow that the proportion of oxygene contained in theair cannot be determined within this quantity. In fact,we find that chemists who have employed such means |239| have found very considerable variations in the quantity ofoxygene of the air; and M. Marti himself, who appears tohave made a great number of experiments with the alcalinesulphurets, and who was acquainted with the precautionswhich they require, fixes it between 0,21 and 0,23. Weshall see hereafter that the eudiometrical means, in whichthe substance which combines with the oxygene is gase-ous, admit of a much greater precision. As we had proposed to ourselves from the commence-ment of our investigation, to ascertain whether the eudi-ometer of Volta was fit to be employed for the analysisof the air, we principally directed our attention to it.This instrument has been accused of being fallacious, ofindicating too small quantities of oxygene in the air;but it appeared to us that supposing it required correc-tions, we might by appreciating them, as well as thelaw of their variations, render it very exact and conve-nient. With this view we proposed to ourselves the fol-lowing questions: 1. When a mixture of hydrogene gas and oxygene gasis inflamed in Volta’s eudiometer, can the absorption ofone of the gases be complete? 2. Is the product of their combination of a constantnature? 3. What is the exact proportion of the two gases forforming water? 4. What are the limits of error that Volta’s eudiometeradmits? We must examine these four questions in succession,but first of all we think it incumbent upon us to give anaccount of the manner in which we prepared the gaseswhich we employed in our experiments. to be continued in our next
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Experiments on the Eudiometrical Means, and on the Pro-portion of the Constituent Principles of the Atmosphere.By Messrs. Humboldt and Gay-Lussac.

(Continued from Page 239.) THE oxygene gas we obtained from the super-oxy-genated muriate of mercury. To obtain it we employeda glass retort, to which had been soldered, by the flameof a lamp, the curved tube through which the gas was topass; and, in order that we might have it as exempt fromazote as possible, we filled the retort about one-fourthwith water. This water being entirely reduced to va-pour before the decomposition of the salt, soon expelledall the air out of the retort; but, in order to prevent theabsorption which would have taken place before the dis-engagement of the oxygene gas, we plunged the ex- |304| tremity of the tube in a saucer filled with mercury, whichwe removed as soon as the gas began to be disengaged.In order that the oxygene may not, passing through thewater, expel azote from it, we convey it directly intothe upper part of the recipient which is to receive it, bymeans of a tube bent at a right angle, which at the oneend ascends to the upper part of the recipient, and at theother is adapted to the first tube by means of a corkstopper, common to both. This process, which is verysimple in its application, is particularly advantageous forthe gases which are soluble in water, such as the carbonicacid gas, the azote oxyd gas, &c. We obtained our hy-drogene gas by decomposing water by means of zinc andmuriatic or sulphuric acid diluted with about six parts ofwater: we took care to fill exactly with acid the vesselfrom which the gas was to be disengaged, and not tomake it pass through the water; but notwithstanding allthese precautions, our oxygene left with the sulphuretfour thousandth parts of azote, and the hydrogene, ana-lysed by other means, shewed six thousandths. Afterthese elucidations let us proceed to the questions whichwe have proposed to ourselves to resolve, beginning withthis: When we inflame a mixture of oxygene and hydrogenegas in the eudiometer of Volta, can the absorption of oneof the gases be complete? In order to ascertain whether all the oxygene or all thehydrogene could be entirely destroyed, we thought thatif two gases were perfectly pure, or if we knew their de-gree of purity, and that their absorption must be com-plete, we should be able to find the same proportion forthe principles of water, whether the hydrogene or theoxygene were predominant. In fact, by detonatingmixtures of 300 parts hydrogene and 100 oxygene, and |305| of 200 of the first and 200 of the second, in which thehydrogene and oxygene alternately predominate, andmaking the corrections due to the impurity of the gases,we obtained very nearly the same proportion. Althoughthe absorption of the two gases might be complete, itwere however possible that the proportions obtained, inmaking them alternately predominate, might not be iden-tical, and this would be the case if, according to the pre-dominance of either of the gases, there were formed anoxygenated or hydrogenated water; but since the propor-tions have become identical, it must necessarily be con-cluded, that the hydrogene and the oxygene were entirelyabsorbed. But though the absorption of the two gasesmay be complete under certain circumstances, it mustnot be supposed that it is so with any quantities; there arenot only such proportions of hydrogene and oxygene, orof their mixture with azote, or even with any other gas,that it is impossible to inflame them by means of theelectric spark; but there are also others with which theinflammation having been commenced, stops before thecombustion is completed. We proceed to cite ex-periments to this effect, which appear to us to be con-clusive. We mixed 100 parts of hydrogene with 200, 300—900of oxygene, and inflamed them by the electric spark:with these different proportions the absorption constantlyamounted to 146 parts; but with 1000 of oxygene it wasat once reduced to 55; with 1,200 and 1,400 it was re-duced to 24 and 14, and with 1,600 it was reduced to 0;that is to say, no inflammation took place. These dif-ferent results are exhibited in the following table. |306|
Hydrogene. Oxygene. Absorption.
100 ‒ ‒ ‒ 200 ‒ ‒ ‒ 146
100 ‒ ‒ ‒ 300 ‒ ‒ ‒ 146
100 ‒ ‒ ‒ 600 ‒ ‒ ‒ 146
100 ‒ ‒ ‒ 900 ‒ ‒ ‒ 146
100 ‒ ‒ ‒ 950 ‒ ‒ ‒ 68
100 ‒ ‒ ‒ 1000 ‒ ‒ ‒ 55
100 ‒ ‒ ‒ 1200 ‒ ‒ ‒ 24
100 ‒ ‒ ‒ 1400 ‒ ‒ ‒ 14
100 ‒ ‒ ‒ 1600 ‒ ‒ ‒ 0 *
What is striking in these different experiments is to see,1, a constant absorption, with very different proportions,change suddenly into a decreasing absorption; 2, thecombustion of hydrogene gas which had commenced,stop before it was completed; 3, that there are such pro-portions of hydrogene and oxygene as cannot be in-flamed. These different phenomena will be in somemeasure explained in the sequel; but in the mean timewe shall remark, that there are even very extended pro-portions with which the combustion of the hydrogene gasmay be complete. The above-mentioned phenomena are not peculiar tothe hydrogene and oxygene gases mixed together, underthe circumstances of which we have been speaking: theyalso take place when we inflame 100 parts of oxygenewith 200, 300—1000, &c. of hydrogene; only it thenhappens, that the term when the absorption ceases to beconstant is more remote; and to comprehend the reason
* The absorptions 68, 55, 24, and 14, are possibly not exact withintwo or three hundredths, for our instruments being too small for thecorresponding proportions, we were obliged to measure them seve-ral times; but this is of no moment with respect to the phenomenonin general.
|307| of this it is sufficient to observe, that in this case theredisappear about 300 parts by the inflammation, whereasthere disappeared only half the quantity in the precedingexperiments.
Azote gas and carbonic acid gas present also ana-logous results. If, for example, we inflame a mixture of900 parts of azote, 100 of hydrogene, and 100 of ox-ygene, the absorption, which ought to be 146 parts, ifthe combustion were complete, was in one experiment,which is that which we take as example, only 50 parts,though in others we have seen it a little above or belowthis quantity. With inferior proportions of azote, wehave constantly had the same absorption of 146. Al-though the azote appears here to comport itself like theoxygene, since with 100 of hydrogene and 1000 of ox-ygene, we had nearly the same result as with 100 of hy-drogene, 100 of oxygene, and 900 of azote, we shall notdraw from hence any inference, because we have not suffi-ciently multiplied and varied our experiments. Neverthe-less, those which we have made tend to prove, that whendeterminate proportions of oxygene gas and hydrogenegas are mixed with different gases, the absorption maybe constant as far as to a certain point, beyond which itdiminishes very rapidly. The absorption of the oxygene and of the hydrogenebeing complete in determinate proportions, and not soin others, it will always be possible, when a gaseous mix-ture is given, which alone would not be able to inflame,to reduce it to another with which the absorption of oneof the gases would be complete, by adding to it oxygeneor hydrogene, or even both together. The combustion of the 100 parts of hydrogene in thepreceding experiment not having been complete, weanalyzed the residue. 100 parts, placed in contact with |308| phosphorus, diminished by 7 in the space of four hours,an evident proof that the residue contained oxygene. Inorder to ascertain whether it had retained hydrogene, weinflamed, in Volta’s eudiometer, a mixture of 200 partsof the preceding residue, 200 of oxygene gas, and 200 ofhydrogene gas; in all 600 parts. After the inflammation312 parts had disappeared; and as, according to experi-ments of which we shall give an account hereafter, 100of pure oxygene require for their saturation 200 of hy-drogene gas, the absorption which, with the hydrogenegas which we have employed, ought only to have been292 parts, amounted to 312, the residuum must necessa-rily have furnished a sufficient quantity of it to carry theabsorption from 292 to 312; that is to say, it must havecontained 13,3 parts. Now calculation shews that itought to have contained 12; it is therefore clearlyproved, that though inflammation took place, the com-bustion was not complete; and that all the hydrogenedid not enter into combination, since we have found thatwhich had not been absorbed in the residuum. We mustobserve, that in all cases in which the absorption was notcomplete the inflammation was languid. From comparing, in the inflammation of hydrogeneand oxygene gas, the effects of electricity with those ofa high temperature, we have been led to believe that theinflammation produced by the electric shock might verylikely be owing to the heat produced by the instantane-ous compression which the electric spark occasions in itspassage. In fact we know, from our own experience,that the inflammation of a mixture of hydrogene and ox-ygene gas depends solely upon the temperature when thisinflammation is produced by heat. For if we cause thismixture to pass very slowly through a tube heated verygradually, from its extremity to its central part, without |309| opposing the free dilation of the gases, the inflammationwill take place as soon as the temperature shall be raisedto a sufficient degree. This being admitted as fact, thatthe inflammation of the oxygene and the hydrogene gastakes place only at a certain temperature, let us see whatpasses in their inflammation by the electric spark. Whenthis passes through a mixture of oxygene and hydrogene,it displaces it by its rapid passage, which does not per-mit the gaseous particles to communicate to each otherthe motion as quickly as they have received it; henceresults a very strong instantaneous compression, whichproduces an elevation of temperature superior to thatwhich is requisite for the combination of the gases, andthe inflammation being thus commenced, must be propa-gated very rapidly. According to this mode of accounting for the effects ofelectricity, we thought that when a weak spark producesonly an imperfect combustion in a mixture of hydrogeneand oxygene gas, a stronger one would produce a morecomplete combustion; but whether it was that we didnot employ a sufficient brisk electricity, or that we didnot multiply our experiments sufficiently, we obtained nosensible differences in employing the spark of an elec-trophorus, three decimeters in diameter, or the shock ofa highly-charged Leyden flask; but the construction ofour eudiometer did not permit us to draw very brisksparks, on which account we shall reserve our opinionrespecting the influence of the force of the electricity inthe inflammation of the hydrogene and oxygene, till weshall have made farther researches upon the subject. In the above-described experiment on the inflamma-tion of a mixture of 900 parts of azote, 100 of oxygene,and 100 of hydrogene, the absorption was not so con-siderable as it ought to have been, and we have proved |310| that the residuum ought to contain what had escapedcombustion; that is to say, it ought to be composed ofsix parts of hydrogene, eight of oxygene, and eighty-sixof azote in the hundred. Therefore, since the combus-tion was interrupted when these proportions took place,it may be concluded that another electric spark wouldno more be able to inflame this mixture. Consequently,in the atmosphere, which contains much less than sixhundredths of hydrogene, the electric spark will not beable to inflame it, or if it does it at the place of its pas-sage, by reason of its great force, the inflammation willnot be able to propagate itself, but will be in a mannerconfined to the places which it traverses. Hence, finally,the inflammation of hydrogene gas, by lightning, and àfortiori by weaker charges of electricity, will not serveto explain the igneous meteoric phenomena; or if thesephenomena are actually results of the inflammationof hydrogene gas, we must conclude that there are morethan six hundredths of it in the air at the moment whenthey are produced.; which is contrary to all probability,especially when we recollect that air, collected at a verygreat elevation, presented no appreciable quantity ofhydrogene above that contained in atmospheric air col-lected at the surface of the earth. But if every time that we cause an electric spark topass into a mixture of hydrogene and oxygene, or ofazote, hydrogene, and oxygene, which is not capable ofinflaming, there is actually produced a local and instan-taneous heat by the compression which the spark occa-sions in its passage, it is possible that by directing a suc-cession of sparks into one of the mixtures of which wehave been speaking, a slight local inflammation might beproduced each time upon the passage of the spark, andthat thus it might be practicable to destroy a determin- |311| able quantity of hydrogene inveloped in a large propor-tion of azote and oxygene, or of oxygene only. Whatseems to confirm this supposition is, that it is well knownthat ether and ammoniac, which are decomposed by heatwhen they are made to pass in vapours through a red-hottube, are likewise decomposed by repeated electricshocks. It would also be interesting to know, whether itbe possible to inflame by the electric spark a proper mix-ture of oxygene and hydrogene, after having dilated itby means of the pneumatic machine. If its inflamma-tion by the electric spark really depends upon the heatwhich this produces by compression, it would be na-tural to suppose, that when these gases are dilated, thecompression by the spark being less considerable, theheat which is produced by it must also be much slighter,and that there may be a degree of dilatation of the gasesat which the inflammation cannot take place. We havenot yet had time to try these different experiments; butwe do not abandon our design to attempt them, which wehope we shall be able to do shortly. To recapitulate: there exist certain proportions of hy-drogene and of oxygene, or of these two gases withazote, in which combustion can be complete. Thereexist also others, in which it stops spontaneously beforebeing completed; and, finally there are proportions inwhich it cannot take place at all. The hydrogene gaswhich escapes the combustion is found again entire in theresidue. When we cannot produce by the electric sparka complete inflammation of the hydrogene gas, or evenwhen we cannot commence it, nothing more is necessarythan to augment the proportions of the oxygene or ofthe hydrogene. The igneous meteoric phenomena can-not be the result of the inflammation of the hydrogenegas, because in the regions where the principal of them |312| are supposed to take place, such as the sudden and abun-dant torrents of rain which sometimes succeed a clap ofthunder, it would be necessary that there should then bemore than six hundredths of hydrogene in the atmos-phere, without which the inflammation could not takeplace; besides which, only the quantity exceeding thisproportion could pass into inflammation. We may account for the cases in which the combus-tion was not complete according to the laws of the affini-ties, by saying, that when one of the gases becomes verypredominant it may defend the other by its affinity, andguard it in part from combustion. Although this affinitymay be very weak, we conceive, with M. Berthollet, howthe quantity of gas may compensate for it; and if therebe in the different gases peculiar properties of stoppingthe combustion sooner or later, this may be explained bytheir different nature. But when we consider the case inwhich the hydrogene is mixed with oxygene only, andsuppose the phenomena of its combustion with differentproportions of oxygene to depend upon affinity, howexplain the sudden transition from a constant absorptionto a decreasing absorption, when it is agreed that if thehydrogene can be prevented from the combination by theoxygene, the effect of the latter must follow a regularlaw? How conceive that these two gases, after havingbeen placed in circumstances favourable to their combi-nation, can by their affinity maintain themselves in theirelastic state, when they might form a much more densecombination, namely, water? How conceive, finally,that an affinity which produces a very great condensa-tion and saturation, can be inferior to an affinity whichproduces no change in the dimensions of the two gases,no saturation? Hydrogene and oxygene, in whateverstate they may be, have the same degree of affinity, as |313| this affinity is measured by their capacity of saturation;only the state in which they are may be more or less fa-vourable to their combination. Now, to say that hydro-gene and oxygene have a greater affinity in the state ofgas than in the liquid state, is to say that their moleculesattract each other more when they are very remote thanwhen they are very near to one another. These objec-tions against an explanation founded solely upon the af-finities, having appeared to us to be of some weight, wehave endeavoured to present one which, in our opinion,did not involve the same difficulties. All combustible bodies require in general a certain ele-vation of temperature, in order to combine with oxygene.Carbon, for example, is not converted into carbonic aciduntil it is red-hot; and this same substance, which at ahigh temperature can continue to burn when it is ex-posed to a current of aqueous vapour, is extinguished assoon as it is immersed in water. This principle, thatbodies in general require a certain elevation of tempera-ture in order to burn, being once admitted, let us sup-pose that we have a body which burns in a given volumeof atmospheric air, and that the temperature necessaryfor the combustion is maintained solely by the heat dueto the absorption of the oxygene: let us also suppose,that at the commencement of the combustion the heatdue to the fixation of the oxygene contained in a cubiccentimeter of air is =1, and that the heat lost during thefixation, whether in radiating heat, or by the absorptionwhich is made of it by the azotic gas or other bodies, is= ½, not taking here into consideration the law accordingto which it decreases. According to these premises, itis very evident that in the first moments of the combus-tion the temperature of the body must rise; but, in pro- |314| portion as the quantity of oxygene shall diminish, andthat of the azote proportionally increase, the heat com-municated will also diminish. A period will thereforearrive, at which the heat lost will be equal to the heatcommunicated, and below which, the temperature beingtoo low, the combustion must cease. What evidentlyproves that the combustion stops only because the tem-perature is too low, is that if we artificially maintainthe temperature sufficiently high, the body will continueto burn. Now this explanation will still hold good, when, in-stead of azote, sulphurous gas, hydrogene gas, carbonicacid, or any other gas, is mixed with the oxygene;only the combustion may cease sooner or later than withazote gas. For it is very evident, that if the sulphurousgas, or carbonic acid gas, had a capacity for caloric,much greater than that of azote, supposing them to bemixed with oxygene in the same proportions as the latter,the loss of heat would be much greater, and consequentlythe cessation of the combustion must take place sooner.But if the gases had equal capacities for caloric, theymust all of them stop the combustion at the same period,as we have seen has nearly been done by oxygene andazote with hydrogene, and this would perhaps afford asolution of the important question, whether the gases haveequal or different capacities. Thus a combustible body, sulphur for example, wouldcease to burn in a determinate volume of air, not becausethe affinity which the azote or the gases produced havefor oxygene were more powerful than that of the com-bustible body; but because the heat absorbed by thesegases, which tend to place themselves in an equilibriumof temperature with the burning body, would be greaterthan the heat proceeding from the fixation of the ox- |315| ygene; whence it would result, that the temperaturewould soon be reduced below that necessary for the com-bustion. In fact, we know that sulphur can continue toburn in air in which it had been extinguished if, we raisethe temperature to a sufficient degree. What takes place in the instantaneous combustion ofthe hydrogene in Volta’s eudiometer, is perfectly ana-logous to what passes in its successive combustion in agiven volume of air, or in that of any other body. Ifwe place a lamp, the flame of which is supplied by hy-drogene gas, under a bell-glass filled with oxygene gas,the flame will become small, bright and slightly coloured.If we replace the oxygene by atmospheric air, the flamewill be more voluminous, less bright, and more coloured.In proportion, especially as the relative quantity of ox-ygene diminishes, the flame will increase in size, be-cause the hydrogene will be obliged to go farther to comeat the oxygene, and the flame will soon be extinguished,although the air still contain some hundredth parts ofoxygene. The phenomena which take place in Volta’s eudiometer are of the same nature. When the propor-tions of oxygene and hydrogene do not deviate muchfrom those which constitute water, the flame is still verybright, notwithstanding its dilatation; but if we mix,for example, 1000 oxygene with 100 of hydrogene, theflame is then weak, of a blueish-green colour, and thecombustion of the hydrogene is far from being complete,for we still find nearly two-thirds of it in the residue.What farther proves that the combustions’ not havingbeen complete was owing to the temperature not havingbeen sufficiently elevated, is that if the residue ismade to pass, as was done by us, through a red-hottube of porcellain, the whole of the hydrogene will beabsorbed. |316| We must observe, that in the combination of the hy-drogene and oxygene gases, a very singular phenomenontakes place, which has long since engaged the attentionof M. Monge. “How does it come to pass,” says this distinguishedphilosopher, “that by elevating the temperature of thetwo gases, or, in other words, by increasing the proportionof the solvent, we diminish the adhesion which it hadwith its bases?” Far from conceiving that the presentstate of our knowledge is competent to give a satisfactorysolution of this question, we wish to recommend it anewto the attention of philosophers. In fact, according to theidea which we are able to form to ourselves of the forcewhich produces the combinations, and of those which areopposed to it, the elastic state indicates that the force ofcohesion is destroyed, and that two bodies in this state arein the condition most favourable to combination; so thatnow that the attractive force of their molecules has beenchanged into a repulsive force, every cause which shallfavour the latter will be in opposition to the former. Ithappens, however, that by raising the temperature of thetwo gases, that is to say, by augmenting their repulsiveforce, their attractive force is increased. It cannot bebelieved, that the heat does nothing more than separatetheir molecules to greater distances from each other; for,in this case, why should a mixture of hydrogene and ox-ygene gas not inflame under the receiver of an air-pump,where it may be indefinitely dilated? Neither is it to besupposed that the heat acting instantaneously can pro-duce a compression which favours the combination of thetwo gases by bringing their molecules into closer contact;for it is easy to convince ourselves that a mixture ofoxygene gas and hydrogene gas, heated very gradually |317| without opposing its dilatation, will nevertheless inflamewhen the temperature shall be sufficiently elevated. Having now proved, that under determined circum-stances the combustion of hydrogene and oxygene maybe complete, we shall proceed to examine whether itsproducts are constant. According to all the experiments which have beenmade on the composition of water, the result has beenconsidered to be uniform. There has, however, some-times been obtained a small quantity of nitric acid; butit has been ascertained that this acid is not a constantproduct of the combustion of the hydrogene, but, on thecontrary, merely accidental. Cavendish was the first whodiscovered this formation of nitric acid, and Messrs.Foureroy, Seguin, and Vauquelin, have taught us howwe may avoid it, and obtain water without any acidity.It has not, indeed, been demonstrated, that oxygenatedor hydrogenated waters have not been formed, because,in all the exact experiments that have been made, thecombustion of the hydrogene gas has always been ef-fected in the same manner, and at most it would beproved that those which have been obtained are constantunder the same circumstances. If we compare the com-bustion of hydrogene gas with that of nitrous gas, theproducts of which are so variable, we shall be still morejustified in concluding, that since oxygene has alwayspredominated in the experiments which have been made,an oxygenated water may have been formed; whereas,if hydrogene had been predominant, a hydrogenated wa-ter would have been the result. Let it then be admitted,that an oxygenated water may be formed; if, for ex-ample, we obtain it in all circumstances, and it be con-stant, this will be of no consequence with regard to the |318| proportion of its principles, which must serve for theanalysis of the air; but if it be so only because the ox-ygene predominated, it is manifest that we shall nolonger obtain the same proportions when we alternatelycause both gases to predominate. to be continued in our next
|365|

Experiments on the Eudiometrical Means, and on the Pro-portion of the Constituent Principles of the Atmosphere.By Messrs. Humboldt and Gay-Lussac.

(Continued from Page 318.) NOW as we have made a great number of experi-ments which prove, that when we employ them alter-nately in excess we constantly, obtain the same propor-tions, it follows, that the combustion of hydrogene gas isof an uniform nature. The Galvanic phenomena of thedecomposition of water seem however to prove that wa-ter is capable of oxygenating or hydrogenating itself;and it is upon this supposition that Messrs. Laplace and Berthollet have accounted for the singular experiment ofthe decomposition of water by two metallic wires im-mersed at one end in this liquid, and communicating bythe other with the two poles of a Galvanic pile. Butwithout wishing to controvert this explanation, whichappears to us the most satisfactory that has hitherto beenoffered, we shall observe that the complete absorption ofthe hydrogene at one of the wires, and of the oxygeneat the other, proves that the water does not becomeoxygenated or hydrogenated, because, in order to be- |366| come so, it would be necessary that it should absorb oneof the gases in a proportion greater than that requiredfor the composition of water. If therefore it absorbsoxygene and hydrogene in exact proportions for formingwater, it must be concluded that the properties of oneof the gases are neutralized by those of the other. Ac-cordingly, in the circumstances of which we are treat-ing, the water might become instantaneously oxygenatedat one of the wires, and hydrogenated at the other; butthe two gases, being deprived of elasticity, and in exactproportions, must soon enter again into combination. If it is well demonstrated that, under given circum-stances, hydrogene or oxygene may be completely ab-sorbed, and, if it is equally so, that the product of theircombination is constant, nothing more remains to bedone, in order to solve the third question, which we haveproposed to ourselves, than to determine the propor-tions of oxygene and hydrogene which constitute water. To 100 parts of oxygene gas we added 300 parts ofhydrogene gas; and after having inflamed them by theelectric spark, we obtained in twelve experiments thefollowing residues:
100,8 101,0 102,0
101,4 101,7 102,0
100,5 102,0 101,0
101,0 101,5 101,5
The mean term of which is ‒ ‒ 101,3
Thus 100 parts of oxygene, supposed to be very pure,required 98,7 of hydrogene: but on placing our oxy-gene gas in contact with sulphuret, we found that it hadall been absorbed within about 0,004; hence it follows,that 99,6 of oxygene absorbed 199,1 of hydrogene, orthat 100 absorbed 199,89, or, to use round numbers, |367| that 100 of oxygene requires 200 of hydrogene for theirsaturation. In the preceding experiments it was the oxygene thatdisappeared. Let us now reverse the experiment, by in-flaming a mixture of 200 parts of each gas; the residueof the different inflammations will be the following:
101,5 102,0 101,5
101,3 102,0 102,3
102,2 101,0 102,0
102,0 101,0 102,0
Mean term ‒ ‒ 101,7
Mean absorption 298,8
200 parts of hydrogene, supposed to be pure, requiredtherefore 98,3 of oxygene; whereas, according to theproportion which we have just established, they ought tohave had 100. But if we admit this same proportion tobe exact in the 298,3 of absorption, there would be only198,8 of hydrogene, which would indicate 0,006 of azotein this gas. Supposing even the hydrogene to be perfectly pure,the two proportions obtained by causing the oxygene orthe hydrogene to predominate, agree sufficiently witheach other to confirm all that has been said in the courseof this memoir: to render them identical, nothing moreis necessary than to suppose 0,006 of azote in the hy-drogene, in which, in fact, we can demonstrate itspresence. We have just seen, from the preceding experiments,that 200 parts of hydrogene, without making any cor-rection, absorbed 98,3 of oxygene. Let us then take theresidues 101,0 and 101,5, proceeding from the combus-tion of 100 of oxygene and of 300 of hydrogene, and de-tonate them with 200 of oxygene gas. In these two |368| residues there must be 0,008 of azote belonging to the200 parts of oxygene gas; and if the remainder 201,7was pure hydrogene it ought to absorb 99,1 of oxygene,and consequently there ought to have disappeared by theinflammation 300,8 parts, but there disappeared only295,0: it follows, therefore, that the residuum 201,7was not pure hydrogene; and that, according to the pro-portion of 100 of oxygene to 200 of hydrogene, it con-tained 5,0 of azote, proceeding from 600 of hydrogene;that is to say, that this last-mentioned gas contained0,008 of azote. We therefore think it proved, that 100 parts, in vo-lume, of oxygene gas require very nearly 200 parts ofhydrogene gas for their saturation. According to theexperiment of Messrs. Fourcroy, Vauquelin, and Se-guin, 100 parts of the former would require 205 of thelatter; but we shall observe, that, whichever of the twoproportions we adopt, the error cannot amount to morethan 0,0035 upon the absolute quantity of the oxygeneof the air, and when the question respects relative quan-tities, the error will be still much smaller. We have ascertained, that the proportion does not varyin consequence of changes of the temperature. It is evi-dent that it must be so, since, as the heat equally dilatesboth gases, and causes them to dissolve equal quantitiesof water, the real weights of hydrogene and oxygenecontained in equal volumes remain always in the sameproportion. It would therefore be more accurate to say,supposing our proportion by the volumes to be well esta-blished, that 100 parts of oxygene require 200 of hy-drogene, than to indicate the proportions of water by theweight. If the oxygene and hydrogene employed for thecomposition of the water had been perfectly dry, or if acorrection had been made according to the quantity of |369| moisture which they might contain, it would be a mat-ter of indifference whether the proportions of its princi-ples were enunciated according to their volumes or theirweights; but since hydrogene combines with oxygene indouble the volume of the latter, and as they both dissolvethe same proportion of water, it is evident that they donot carry into the combination quantities of water whichare in the same reciprocal proportions as the quantities,by weight, of oxygene and of hydrogene, and that con-sequently the proportion of the principles of the watermust thereby be altered. Thus the proportion, accord-ing to the volumes, has the property of remaining con-stant, notwithstanding the changes with regard to tem-perature and moisture, whilst that, according to theweights, varies under the same circumstances. And letit not be imagined that this consideration is of little im-portance: for it would be very easy to prove that it hasvery considerable influence upon the proportion of theprinciples of water. According to the experiment ofMessrs. Fourcroy, Vauquelin, and Seguin, the most ac-curate that has hitherto been made upon this subject, wa-ter contains by weight 85,662 of oxygene and 14,338 ofhydrogene. But the experiment having been made at atemperature of about 14°, and the correction due to thewater held in solution by the gases not having beenmade, it follows, that if we adopt their specific weightof the oxygene and hydrogene gases, as well as the pro-portion of their volumes in their combination, and more-over admit with Saussure, that a cubic foot of air, at thetemperature of 14°, contains very nearly 10 grains ofwater in solution, the proportion by weight between theoxygene and hydrogene, instead of being 85,662 to14,338, would be 87,41 to 12,59; a very remarkabledifference, and which especially must be of great in- |370| fluence in analyses where the real weight of the hydro-gene is to be determined. The same consideration ap-plies also to the specific weight of the gases, and princi-pally to that of the hydrogene, of which about a sixthpart is due to the water which it holds in solution whenthe temperature, as here supposed, is 14° Reaumur. Wedo not therefore doubt, that if we had hydrogene gasperfectly dry, and deprived of the azote gas, which ap-pears very often to accompany it, we should find its spe-cific lightness to be at least 15 times greater than that ofthe atmospheric air. It still remains for us to answer the last question whichwe have proposed to ourselves, and to shew what are thelimits of the error in Volta’s eudiometer; and next,what are the smallest quantities of oxygene or of hydro-gene that can be estimated by his method. The effects obtained with this instrument, being in-stantaneous, are independent of the thermometer andbarometer. In this point of view, it has the very de-cided advantage over phosphorus and the alkaline sul-phurets, of giving results very capable of comparison;but this is not the only one; it has also that of the eu-diometrical means which give multiples of the quantityto be estimated. As in this instrument each hundredthof oxygene is represented by a three times greater ab-sorption, the error that can be committed amounts onlyto a third upon this gas; and now, especially as we haveinstruments which divide the measure into three hundredparts, it is evident, that if we err even by one division,the accuracy, as to the quantity of oxygene, may becarried to near a thousandth part of the quantity of airanalyzed. If therefore the results of the combustion of hydrogenegas admit so well of comparison, and the errors to which |371| they are liable are restricted within such narrow bounds,it is evident that we may not only find the slight diffe-rences which exist between two portions of atmosphericair, but also determine less than three thousandth parts ofoxygene which shall be lost in azote or hydrogene gas:but in this case, in order that the inflammation take place,it would be necessary to add a given quantity of oxygene,the absorption of which with hydrogene gas had been de-termined by previous experiments, and then the excessof the first absorption above the second would be attri-buted for a third to the oxygene gas contained in the airwhich is analyzed. On the other hand, in order to determine whether oneportion of hydrogene be more pure than another portion,or whether there exist very small quantities of it in a gasor in the atmospheric air, it would be necessary, in thefirst case, to mix 100 parts of hydrogene gas with 100 ofoxygene: the quantities of real hydrogene would be inthe direct ratio of the absorptions. But if the proportionof hydrogene were very small, for example one twohundredth, it would be necessary, in order to effect itscombustion, to add 100 parts of this gas to 200 of the airto be analyzed, and to detonate the mixture with a suffi-cient proportion of oxygene. By this means, and withthe practice which we have now acquired, we have beenable to find again three thousandth parts of hydrogene gaswhich we had mixed with atmospheric air. It might be objected against Volta’s eudiometer, thatthe hydrogene not being always the same, we might incurerrors difficult to be appreciated. We shall first observethat it is indifferent whether or not it contain azote; butif it contained oxygene, its quantity confounding itselfwith that which we wish to appreciate, would alter theresults. In order to avoid this inconvenience, we may |372| first of all detonate separately 500 parts of hydrogene with100 of oxygene; by this means its oxygene will bedestroyed, and we may then employ it for the analysis ofthe air. With this precaution we may employ a gas pre-pared as inaccurately as possible. It is sufficient if it havebeen extracted from the water by means of zinc and sul-phuric acid or muriatic acid; for it is well known that ifwe employ another metal, such as iron, the gas is nolonger of the same nature. After all the experiments which we have recorded, wemight have been justified in concluding that the eudio-meter of Volta must indicate the whole of the oxygenecontained in the atmospheric air; but we wished to de-termine this point by direct experiment. We analyzedan air composed of 20 parts of very pure oxygene and 80of azote, obtained from the decomposition of ammoniac byoxygenated muriatic acid, all possible precautions beingtaken to prevent its becoming mixed with atmospheric air.200 parts of this air, inflamed with 200 of hydrogene gas,gave five absorptions, the greatest of which differed fromthe smallest only by 5,1000 and the mean term of whichwas 124,9. These 124,9 parts indicate 41,6 of oxygene,of which the half 20,8 corresponds to 100 of our factitiousair. We find therefore 0,008 of oxygene more than wehad employed, which might seem to indicate that theproportion of 100 of oxygene to 200 of hydrogene is ra-ther too great; but we must observe that our hydrogene,though carefully prepared, still emitted light with phos-phorus, and that in order to explain our result, it is suffi-cient to suppose that the azote contained a hundredth partof oxygene, which is sufficiently probable if we considerthat the oxygenated muriatic acid is very speedily decom-posed by the action of light. It appears from what has been said, that the results af-forded by Volta’s eudiometer admit very well of compa- |373| rison, and that the limits of their differences may be re-duced very nearly to a thousandth part of the air ana-lyzed. It appears also that by its means we may estimatevery minute differences between two airs or very smallquantities of hydrogene mixed with the atmospheric air.Independently of the property which this instrument pos-sesses of indicating the whole quantity of oxygene con-tained in an air, it is the only one with which we can as-certain the proportion of hydrogene in a gaseous mixture,and in this point of view it still merited to have its modeof acting attended to and studied. Thus the illustrious Volta, to whom Natural Philoso-phy is indebted for so many beautiful discoveries, has alsothe merit of having furnished Chemistry with the mostaccurate and valuable instrument for analyses.

Analysis of the Atmospheric Air by Volta’s Eudiometer.

As we have now proved that Volta’s eudiometer givesresults very capable of comparison, that it can indicatethe whole quantity of oxygene contained in the air, andthat it has over the other eudiometrical means in whichthe absorbing substance is solid or liquid, the advantageof giving multiples of the quantity of oxygene to be esti-mated; we shall proceed to apply it to the analysis of theair. If the proportion of 100 of oxygene and 200 of hy-drogene which we have established be strictly correct, weshall obtain the proportion of the oxygene to the azotelikewise correct; but supposing even that the quantity ofhydrogene were too large or too small by 5 parts, the er-ror would not amount to more than three thousandth partsof the air analyzed, and we should have the advantage ofobtaining a greater precision than by any of the otherknown eudiometrical means. |374| The atmospheric air which we have analyzed was col-lected over the middle of the Seine in cold, temperate andrainy weather, and during the prevalence of differentwinds. In order to obtain a greater parity between thecircumstances, and better to appreciate the differences inthe nature of the air, if there were any, we analyzed onthe same day the different portions of air which we hadcollected in different weathers, and which we had pre-served in glass vessels well closed and inverted over thewater. For brevity’s sake, we have comprized in the ta-ble annexed to this memoir, the absorptions produced bythe inflammation of 200 parts of air and 200 of hydrogenegas, and have at the same time indicated the corre-spondent quantities of oxygene. It will there appear that our experiments prove, in thefirst place, that there are no variations exceeding a thou-sandth part in the quantity of the oxygene of the air,though that which we analyzed, having been collectedduring the prevalence of different winds, came from re-gions very remote from each otber; and in the secondplace, that the proportion of the volume of the oxygeneto the other gases which exist in the air, is as 21 to 79.The first result, that the air does not vary in its composi-tion, is rigorously exact, because it is independent of theproportion of the hydrogene and oxygene gas which con-stitutes water; but the second result, that the air contains21 hundredths of oxygene, can also deviate but very lit-tle from the real truth; for if we suppose that the quan-tity of hydrogene required for saturating 100 parts of ox-ygene were larger or smaller by 5 parts than that whichwe have assigned (and which we have reason to believe iscorrect within a much less difference), the error with re-spect to the proportion of oxygene which we have foundin the air, would not amount, as we have already ob- |375| served, to more than three thousandth parts of the airanalyzed. But as many meteoric phenomena may be attributed toinflammation of hydrogene gas, it has been endeavouredto explain them by admitting the existence of this gas inthe atmosphere. We therefore thought it a very interest-ing enquiry, to investigate whether the air actually con-tains hydrogene gas; and in order the more easily to dis-cover it, we made a gaseous mixture, in which we weresure that there was none of it, and we made a compara-tive analysis of the two airs. We made a mixture of 20parts of oxygene and 80 parts of azote, obtained fromammoniac by means of the oxygenated muriatic acid, andwe detonated 300 parts of each of the two airs with 100of hydrogne; but the result of six experiments madewith the atmospheric air was exactly the same as that ofsix others made with the factitious air. And as we haveshewn that we could appreciate less than three thousandthparts of hydrogene, it must be concluded that the atmos-phere does not contain this gas, or if it contains it, itsquantity does not amount to three thousandth parts. Itcannot however be doubted that there exists a little hy-drogene in the air; some is daily evolved from marshes,but its quantity may be so small (a thousandth for exam-ple) as to elude all our means. The proportion of car-bonic acid existing in it ought to be much more conside-rable, if we reflect upon the abundance of the sourceswhich furnish it, and yet, if it did not form insolublecombinations with lime and barytes, it would perhapsstill remain to be ascertained by the determination of itsvolume whether any of it existed in the air. The car-bonic acid, it is true, cannot accumulate in the air, be-cause vegetation decomposes it; but is it proved thatthere do not exist causes which return the hydrogene |376| to the earth, and thereby prevent it from accumulating inthe air? To draw a conclusion from the preceding experiments,we shall say: 1, that the atmosphere does not vary generallyin its composition; 2, that the quantity of oxygene which itcontains is 21 hundredths; 3, finally, that it does notcontain any hydrogene which we are able to appreciate. This identity of composition in which the principles ofthe atmosphere are constantly maintained, and this ab-sence of hydrogene which our experiments prove, mustgive confidence to the Geometrician with respect to thetheory of refractions. The refractive power of the diffe-rent gases being different, and that of hydrogene beingstronger than that of oxygene and of azote, the theoryof refractions, which is founded only upon the vari-ations of the barometer and thermometer, would be veryimperfect if the atmosphere changed in its constituentprinciples; but fortunately it is easy to prove that thesechanges do not take place in a sensible degree, andthat the hydrogene gas, the refractive power of which isvery great, does not exceed 0,003, at least as far as thegreatest heights to which men have ever ascended. TheGeometrician will therefore have nothing else to considerin the Theory of Refractions than the barometer, thethermometer, and the hygrometer. In fact, a little reflexion will be sufficient to convince usthat the atmosphere cannot vary very considerably in thespace of some years, and still loss of some days, at leastif we do not speak of some very particular local variations.For if it varied thus in so short a space of time, by whatmiracle should it do so, and return suddenly to its originalstate? How conceive a cause sufficiently powerful tochange from one day to another the proportion of oxy-gene by a thousandth part only, unless we should admitthe existence of a magnetic or electric power, or any |377| other equally imaginary, which could change, by un-known modifications, the oxygene into azote, and viceversâ? It is possible that the atmosphere varies veryslowly both in the proportion of its principles and inits weight; but these variations, for being so insensible,ought not the less to engage the attention of philo-sophers. If it is now well proved that in general the atmospheredoes not vary in its composition, we must seek for thecause of the differences which some have imagined theyhad discovered in it, in the local circumstances underwhich it was analyzed. Volcanoes upon high mountains,particular fermentations, water issuing from a marsh or alake, might perhaps in some degree impair the purity ofthe air in contact with them, either by depriving it ofoxygene, or by exhaling into it non-respirable elasticfluids; but how trifling must not this diminution of theproportion of the oxygene be in so large a mass of conti-nually agitated air, when we consider that in places wherea great number of individuals is collected, or in thosewhere there seems to exist a focus of infection, the airnevertheless experiences but very slight variations. Wehave analyzed two portions of air, one of which was col-lected in the pit of the Theatre Français, immediately be-fore the curtain was raised for performing the after-piece,three hours and a half after a great number of spectatorshad assembled, and the other of which was collected threeminutes after the entertainment had ended in the mostelevated part of the house. These two portions scarcelyrendered lime water turbid; the atmospheric air indi-cating 0,210 of oxygene, the air of the pit indicatedonly 0,202 and that of the highest part of the house0,204. |378|
Analysis of the at-mospheric air. Of the air of the pit. Of the air of the highestpart of the building.
200 atmosph. air. 200 atmosph. air. 200 atmosph. air.
200 hydrogene. 200 hydr. 200 hydr.
126 air absorbed. 121,5 abs. 122,5 abs.
21 oxygene. 20,2 oxyg. 20,4 oxyg.
M. Seguin has also analyzed the air of hospital wardswhich he had kept closely shut up for the space of twelvehours, and found it to be almost as pure as the atmo-spheric air, although it had an insupportably infectioussmell. If therefore, even under circumstances the most favour-able to the absorption of the oxygene, the air does notlose one hundredth part of it, we cannot thereby accountfor the sense of anxiety which we feel in close andcrowded apartments, or the maladies which are peculiarto the vicinity of lakes and marshes, or to certain coun-tries. Under some circumstances they will be producedby emanations which elude all our eudiometrical means,and which act in a peculiar manner upon the human body.Thus a bubble of sulphurated hydrogene gas, of oxyge-nated muriatic acid, a putrid exhalation, even a flower,may fill an immense space with this odour, and astonishour imagination by their extreme subtility, even whenwe are ready to sink under their action. The pestilentialmiasmata may be equally subtile without being the lessdeleterious, and equally elude all our means of analysis.Fortunately, if we cannot seize these atomic substancesand determine their nature, we may at least, after thelabours of M. Guyton, which have been productive ofsuch great benefit to mankind, destroy their action. Butunder other circumstances the maladies may arise from |379| the humidity of the air, from its temperature, from itselectric state, or in general from the state of the atmo-sphere with respect to the peculiar state of the individualaffected; and in these cases, which may be very frequent,the malady may make great ravages without its beingpossible to arrest its progress: it would therefore be illu-sory to attribute all to a single cause, when the state ofhuman health depends upon the concurrence of all thecircumstances under which men are placed. But let us now recapitulate the principal facts con-tained in this first part of our Memoir, and call to mindsome of the explanations which we have offered, hopingwe may be permitted to consider them as expressing thereal state of the facts. The solution of an alkaline sulphuret, when made cold,does not absorb the azote, and it may be employed withadvantage for the analysis of the air: when made hot, itabsorbs it, and indicates a greater diminution of volumein the air than that which proceeds from the absorptionof the oxygene. It is to the water only, and not to thesulphuret, that we are to attribute this property. There are certain proportions of oxygene and hydro-gene in which the combustion produced by the electricspark may be complete; there are others in which thecombustion ceases before being completed; and finallythere are others in which it cannot take place at all.These last phenomena seem to depend upon the circum-stance that the temperature necessary for the combustionis not sufficiently elevated, and not upon the mutual affi-nity of the gases: for in all cases in which the combus-tion is not complete, we need only raise the temperatureartificially in order that it may become so. When thehydrogene and oxygene are not entirely absorbed, we |380| find them again in the residues, and prove that they havenot formed new combinations. When we cannot inflame a gaseous mixture which con-tains oxygene and hydrogene, it will be sufficient to aug-ment the proportion of these two gases. The meteoricphenomena cannot be results of the inflammation of hy-drogene gas, since even in an air consisting merely ofpure oxygene, it would require more than 6 hundredthsof hydrogene for combustion to take place, and even thenit would be only partial. Electricity seems to act in theinflammation of oxygene and hydrogene gas by the heatarising from the compression which it produces in itspassage through their mixture. These two gases, bytheir combination, form water, which is constant in itsnature. If the galvanic phenomena seem to prove thatwater is susceptible of oxygenation or hydrogenation, theymay be equally well accounted for without the aid of suchan hypothesis. One hundred parts by volume of oxygene require fortheir saturation 200 of hydrogene. This proportion isindependent of the changes of temperature and moisture,whereas that determined by weight varies under the samecircumstances, because the two gases do not carry into thecombination quantities of water which are in the sameproportion as their quantities by weight; whence it resultsthat the proportions of the water which have been esta-blished must be modified. The Eudiometer of Volta iscapable of indicating the whole quantity of oxygene con-tained in a given volume of air within about a thousandthpart of that volume, and its results admit very well ofcomparison. In the present state of our knowledge, it isthe most exact of our eudiometrical means; it is not onlycapable of indicating very small quantities of oxygene orof hydrogene, and determining the purity of the last- |381| mentioned gas, but it has likewise the advantage of givingmultiples of the quantity to be estimated. It has there-fore in all these respects a very decided superiority overthe other eudiometrical means. The atmosphere containsonly 0,21 in volume of oxygene, and it does not vary inits composition. It contains no hydrogene, or if it con-tains any, its quantity cannot amount to 3,003. to be concluded in our next
|449|

Experiments on the Eudiometrical Means, and on the Pro-portion of the Constituent Principles of the Atmosphere.By Messrs. Humboldt and Gay-Lussac.

(Concluded from Page 381.)

Of the Nature of the Air extracted from Water, and of theAction of Water upon the Gases, both pure and mixed.

WE have hitherto examined the eudiometrical meanswhich lead to the exact analysis of the atmospheric air.We should undoubtedly have confined ourselves to theenunciation of the principal facts to which the first partof our investigation has conducted us, had we not re-marked in the course of these experiments, and particu-larly of those upon the sulphurets, that water and otherliquids exert an action upon the air which may frequentlybecome a cause of error, the more important as it hashitherto been little attended to. We therefore appre-hended, that we should leave our labours in a still moreimperfect state than we have already done, if we hadnot directed our inquiries to this action of water upon thegases, both pure and mixed, which are subjected to it.The experiments which we have made with a view tothis object, shall form the conclusion of our memoir. |450| It is generally known that water can hold air in solu-tion. Boyle, Huggens, and Mairan, have discussed thisfact; but they did not possess the means of discoveringthat this dissolved air differs chemically from the atmo-spheric air. The celebrated Priestley was the first whoobserved that the air extracted from water contains moreoxygene than common air. M. Hassenfratz afterwardsasserted that rain-water evolved an air which containednearly forty-hundredths of oxygene; and Messrs. Ingen-houtz and Breda, in their experiments upon nitrous gas,were led to similar results. But if it is already known that the air contained in wa-ter is more pure than atmospheric air, it has also beenmaintained that water absorbs the oxygene gas moreabundantly and more readily than the azote. M. Four-croy even mentions the curious fact, which however hehimself does not conceive to be sufficiently authenticated,that water charged with oxygene gas absorbs hydrogenegas, upon which common water has hardly any action.We shall see hereafter, that that which it exercises uponany gas is modified by the nature of the air which it al-ready holds in solution. Mr. Henry, in a memoir lately published in England,has examined the absorption of different gases by waterdeprived of air. He effected these absorptions under a pres-sure equal to that of two or three atmospheres; but he hasnot treated of the mixture of different gases, nor of theaffinity which water has for this mixture: he confineshimself to the examination of the quantity absorbed, ac-cording to the difference of temperature and of barome-tric pressure, without directing his inquiries to the ac-tion of water already saturated with other gases. We conceived that we ought not to neglect a subjectso intimately connected with eudiometrical inquiries, andto which chemists have hitherto paid so little attention. |451| We have examined the degree of affinity by which theoxygene dissolved in water is retained in it, according tothe temperature and the salts which it may contain. Weplaced in contact with water equal quantities of gases,both pure and mixed, and we observed the changes whichthese mixtures undergo in their chemical composition.Finally, we have begun to examine a problem of greatimportance to meteorology, namely, whether rain waterholds hydrogene in solution. All these inquiries, which we intend to prosecuteduring the course of this year, and particularly upon themountains which we purpose to visit, are not as yet in avery advanced state; we shall therefore content ourselvesfor the present with offering some leading facts, which,we trust, will not be deemed altogether destitute of in-terest by philosophers. After mixing the whole mass of air which water yieldsby boiling, without separating the portions first disen-gaged from those evolved at the end of the operation,we found by Volta’s eudiometer that distilled water,which has re-absorbed atmospheric air, gives an air whichcontains in the hundred parts 32,8 of oxygene; the wa-ter of the Seine, one which contains 31,9 oxygene; andrain-water an air containing 31,0 of the same principle. From these experiments it follows, that we may ex-tract from these three waters air nearly equally rich inoxygene, and purer by ten-hundredths than the atmo-spheric air. This quantity of oxygene is more variablein the waters of wells, which in the bowels of the earthare in contact with substances that exercise an affinityupon oxygene. Water of the Seine, collected at anotherperiod, yielded an air containing only 29,1 of oxygene,an air somewhat less pure than that of the rain water. If distilled water which has again absorbed air, rainwater, and river water, yield airs all of which are much |452| purer than the atmospheric air, it will be still more inte-resting to examine the nature of the gaseous mixtureswhich water yields when heated gradually. It is in theseexperiments that the great affinity of oxygene for this li-quid displays itself in its strongest light. We graduallyheated water of the Seine to ebullition, and collectedthe air which is disengaged by successive and unequalportions. We took 200 parts of these portions, and ha-ving detonated them with 200 parts of hydrogene gas,they gave us the following results.
Portions of air, accordingto the order of theirevolution. Absorption. Oxygene gas containedin 100 parts of theair evolved.
First ‒ ‒ ‒ 142,0 ‒ ‒ ‒ 23,7
Second ‒ ‒ ‒ 164,5 ‒ ‒ ‒ 27,4
Third ‒ ‒ ‒ 185,0 ‒ ‒ ‒ 30,2
Fourth ‒ ‒ ‒ 195,0 ‒ ‒ ‒ 32,5
These experiments, several times repeated, prove thatwater abandons at first an air, the purity of which is onlya little superior to that of atmospheric air; after whichthe purity of this air, or the disengagement of oxygene,progressively increases, and the last gaseous portionswhich the heat separates contain the most oxygene. Onrepeating this experiment upon snow-water, the firstportions of air had 24,0; the last 34,8 of oxygene. Pos-sibly if the mass of water were heated still more slowly,and the small portion of air which is first evolved care-fully separated, we should have at the beginning of theoperation an air still less pure than that which we obtained. Water therefore does not exercise an uniform actionupon oxygene and upon azote, and elevation of tempera-ture diminishes its action upon the first less than uponthe last. It is even probable that the portion of air whichis disengaged towards the end of the operation would beof greater purity than that of 32 or 34 per cent. of oxy- |453| gene, if the water contained in the vessel which receivesthe gaseous mixture did not begin to be heated, and toevolve its air, which then is only at 23 per cent. of oxy-gene. This disengagement takes place especially whenthe aqueous vapour begins to pass, and it is this dimi-nution of the purity of the air expelled last and the ine-quality of volume of the four separate portions, whichexplain how the whole mass of air extracted at oncecontains to the amount of 31 hundredths of oxygene. This unequal action of water upon the oxygene and theazote manifests itself also in the solution of salts. Wehave observed that the pure water of the Seine gave byebullition nearly one half more of air than the same watercharged with muriate of soda. The cause of this dimi-nution consists in the very considerable quantity of airwhich already disengaged from the water, still cold,whilst the solution of the salt is taking place. This air,accurately analyzed, shewed only 0,225 of oxygene,whilst the air obtained by boiling the water charged withmuriate of soda, contained 0,305. Hence it appears thatthe water, in dissolving the salt, abandons a part of theair which it holds in solution, but that this part con-tains oxygene in a less proportion than that which it re-tains. The condensation which water experiences in passingfrom the liquid to the solid state presents to us a thirdclass of phenomena analogous to those which we have justdescribed. Melted ice yields only about half the quantityof air which we obtain from common water, and it is tobe observed that it does not begin to evolve its air untilits temperature has been raised as high as above the six-tieth degree of the centigrade thermometer. The air ob-tained, divided into two unequal portions, shewed in Volta’s eudiometer 27,5 and 33,5 of oxygene. Then thepurest air was again evolved the last. |454| The small quantity and the great purity of the airevolved from melted ice, proves that water, as it passesinto the solid state, abandons a large portion of its air,and that this part, separated during the congelation, isair of much less purity than that which it retains. Thusthree phenomena, which at the first view appear diffe-rent, water at a temperature from 35° to 40° centigram,water dissolving salts cold, and pure water congealinginto ice, present results entirely similar to each other intheir action upon oxygene and azote. A moderate tem-perature acts like the solution of a salt, and this like thetransition from the liquid into the solid state. The waterin these three cases evolves an air of less purity than thatwhich it holds in solution. It is a very remarkable phenomenon that the congela-tion of water into the state of snow expels less air fromit than the formation of ice. We melted some newlyfallen snow, and heating it gradually, we obtained a vo-lume of air nearly twice as great as that which melted iceyields. The air extracted from the snow-water was al-most in equal abundance with that evolved from the wa-ter of the Seine; for the latter gave by ebullition 1940measures of air, while the same volume of snow-wateryielded 1892. These 1892 parts collected into 5 por-tions, according to the periods at which they were ex-pelled by the heat, shewed successively in Volta’s eudi-ometer.
The first ‒ ‒ ‒ ‒ ‒ 24,0 of oxygene.
Second ‒ ‒ ‒ ‒ 26,8.
Third ‒ ‒ ‒ ‒ 29,6.
Fourth ‒ ‒ ‒ ‒ 32,0.
Fifth ‒ ‒ ‒ ‒ 34,8.
This last portion of air is the purest we have yet ex-tracted from any water. |455| The volumes of each portion being known, calculationgives us for the purity of the air considered collectively28,7 of oxygene. The water of the Seine yielded on thesame day an air which was less pure by \( \frac{4}{1000} \). Other-wise the two waters, that of melted snow and that of theriver, give a volume of air equal to nearly \( \frac{1}{23} \) of theirown. These experiments upon snow-water and upon meltedice, which we design hereafter to vary in many ways,present considerations of great importance to the study ofmeteorology. Snow is nothing else than an aggregate ofsmall crystals of ice which are formed in the higherregions of the atmosphere, and yet these small crystalsmelted give a volume of air nearly twice as great as thatwhich the ice formed upon our rivers yields. Hence it is tobe concluded that when the water dissolved in the air con-geals into snow, it does not expel that large portion of airwhich it disengages in its congelation upon the surface ofthe earth, unless we might be allowed to suppose thatsnow retains between its small crystals a certain quantityof air which it absorbs as it melts; for it appearsthat it is principally at the moment of its congela-tion that water abandons the greater part of its air. The beautiful vegetation which surrounds the Gla-ciers, the rapid developement of plants when the snowmelts in the spring, and several phenomena which aresupposed to have been observed in agriculture and inbleaching, have led to the notion that the waters of ice,snow and rain, produced peculiar effects by a large quan-tity of dissolved oxygene which was evolved from them.The experiments which we have hitherto made do notseem favourable to these conjectures. There undoubt-edly exist wells, the waters of which contain air inferiorin purity to the atmospheric air, and we do not doubtthat these waters, charged besides with salts and car- |456| bonic acid, must have an influence upon vegetation andbleaching very different from that of snow-water. Butthe differences produced by distilled water exposed to theair, rain-water, snow-water and the water of the Seine,are not easily to be accounted for by the oxygene dis-solved in them, if we recollect that all these airs containwater of nearly equal purity, and that they contain it inalmost equal quantity. The phenomena of vegetation,like those of meteorology, are so complicated; they de-pend upon the concurrence of so many causes at once,that we must be very careful not to attribute to one whatis the effect of many. The experiments which we have recorded on the forcewith which the last particles of oxygene dissolved are re-tained by water, throw an additional light upon the statein which air exists in liquids. The specific gravity ofdistilled water and of that charged with air, being appa-rently the same, Mairan has concluded with reason thatthis air cannot be lodged in the fluids in an elastic state.The chemical phenomena confirm this opinion. If waterdeprived of its air by distillation, or by the air-pump,could be considered as a sponge the pores of which areempty, how should these pores not fill themselves on thefirst contact with atmospheric air? But this solution of airin water can be considered only as the effect of a chemicalaffinity; for how but by this affinity could the absorptionof the gases by the water deprived of air be so slow, andabove all, how else should the water dissolve one gas inpreference to another? How should water charged withone species of air abandon a part of it, as we shallsee hereafter that it does, to receive another of a differentnature? After having examined the air which may be extractedfrom water under different circumstances, we shall con-clude our Memoir with the experiments which we have |457| made in placing gases, both pure and mixed, in contactwith water. The gases which we employed were exactlyof the same volume, and the quantity of filtrated water ofthe Seine was nearly equal. After a space of from 6 to8 days, we not only measured the quantity of the volumesabsorbed, but we also analyzed the residues. This ana-lysis was the more necessary as one might often betempted to conclude from a very small change in the vo-lume of the gas placed in contact with the water, thatthe latter has no sensible action upon it, whilst the na-ture of the residue indicates that this action has beenvery strong, but disguised by the quantity of air evolvedfrom the water in lieu of that which has been ab-sorbed. Of all the gases, the oxygene is that which the waterof the Seine absorbs in the most considerable quantity.If we place in contact with this water, already chargedwith air, 100 parts of oxygene gas, 100 of azote, and 100of hydrogene, the oxygene gas will have diminished by40 parts when the two others have lost only 5 and 3 parts.But the real absorption of the oxygene gas is still muchmore considerable than its apparent diminution indicates.The 60 parts of residue, instead of being pure oxygene,contained 37 parts of azote and only 24 of oxygene; sothat the 100 parts of oxygene employed, had lost uponthe Seine water 77 parts, which had expelled 37 parts ofazote. Thus a river water which had been exposed fora long time to the atmosphere, and which might be con-sidered as saturated with air, absorbs a large quantity ofoxygene when it is presented to it. It takes it, withoutabandoning a portion of azote equal in volume to the oxy-gene absorbed. The action of water upon the volume of hydrogenegas appears to amount almost to nothing. The inequa- |458| lity of the results which we obtained prevent our sayingany thing concerning the slight changes which it mayundergo during their contact. The volume of pure azote gas diminishes upon thewater by between 2 and 3 hundredth parts; but the re-sidue is no longer pure azote: we discovered in it11 parts of oxygene which had been displaced fromthe water by 14 parts of azote. The azote therefore dis-lodges ozygene from the water, as oxygene dislodgesazote. The action is analogous, but the quantities ab-sorbed and dislodged are different. The contact of the river-water with a mixture of hy-drogene and oxygene gases was examined under vari-ous circumstances. Sometimes we mixed the two gasesin equal quantities, sometimes we caused one or the otherto predominate. The diminution of the volume of thegases is greater when the oxygene predominates; thatis to say, when we expose to the water a mixture of 200parts of oxygene with 100 of hydrogene. In all these ex-periments azote is again dislodged from the water. Inanalyzing the residuum of a mixture of equal parts of ox-ygene and of hydrogene, we found in 100 parts 20 partsazote, 50 hydrogene, and 30 oxygene. The greater theabsorption of oxygene was, the more azote we found tobe dislodged. Having mixed 400 parts of oxygene with200 of hydrogene, this volume was reduced upon Seinewater, in the space of ten days, from 600 parts to 562.If this residue had undergone no chemical change in itsproportions, if no other gas had been dislodged, itought to have contained 375 parts of oxygene and 187of hydrogene; but our analysis shewed it to contain 246azote, 142 hydrogene, and 174 oxygene. These experiments prove that hydrogene, which, whenplaced alone in contact with water, is not sensibly ab- |459| sorbed by it, is dissolved in it, and that in a very consi-derable proportion, when it is mixed with oxygene. Onthis subject a question of great importance to NaturalPhilosophy presents itself; namely, whether this hydro-gene absorbed by the water exists in it in the state of hy-drogene, or whether it combines in it with oxygene andso forms water. We have endeavoured to solve thisquestion by leaving a mixture of hydrogene and oxygenein contact with water recently deprived of all its air byebullition. After the space of 12 days, we distilled thiswater, and on analyzing the air disengaged from it, wefound the hydrogene to exist in it in such abundancethat we could inflame it in Volta’s eudiometer withoutadding to it any other gas. This experiment proves be-yond a doubt that the hydrogene absorbed is found againin the water. But did this water give up again the samequantity which it had absorbed? Would not this hydro-gene dissolved in the water unite with the oxygene if ithad been lodged in it for several months? We design tomake a long series of experiments upon this subject. Ifthe hydrogene and oxygene contained in the water couldcombine in it, we should be able more readily to conceivehow the hydrogene gas which rises from the surface ofthe earth is not to be discovered either in the air whichsurrounds us, or in the high regions of the atmosphereinto which we have ascended. We must recollect uponthis subject that having carefully examined rain-water,in order to discover hydrogene in it, we have ascertainedthat the air disengaged from this water did not containa quantity of it amounting to \( \frac{3}{1000} \). We shall repeatthese experiments upon rain that has fallen in diffe-rent seasons, and particularly during storms. River water placed in contact with mixtures of gaseshas in general acted less upon the mixtures of oxygene |460| and azote than those of oxygene and of hydrogene.This result will appear the less surprizing if we takea general view of what takes place in these phenomena. We find that water has a continual tendency to placeitself in a state of equilibrium with the gases presentedto it. If we present oxygene to it, it abandons azote.If we place it in contact with azote, it abandons oxy-gene. If we present to it a mixture of oxygene andhydrogene, it absorbs a part of these two gases, and re-places them with azote. It every where tends to modifythe proportions of the air which it holds in solution ac-cording to the nature of the gases which are presented toit. Now the water of the Seine being charged with amixture of azote and of oxygene, it seems natural that itshould excite more action upon a mixture of hydrogeneand oxygene than upon that of azote and oxygene,which is analogous to the air which it holds in solution.In order to obtain an accurate idea of these phenomena,we shall make experiments upon water recently deprivedof air, by charging it with different gases both pureand mixed, and examining the action of this waterafter a long space of time; for frequently it is nottill after a long repose that nature is enabled to overcomethe obstacles which oppose themselves to the action of theaffinities. Here we shall conclude the account of the inquiries intowhich we have been engaged for several months past.The more extensive the field is which we purpose to ex-plore, the more strongly we feel the imperfection of thework which we now present to the public; but this sen-timent, so far from discouraging us, will only render usthe more assiduous in interrogating nature, in order thatwe may carry these researches to a higher degree of per-fection. |461| TABLE Representing the Analysis of the Air.
Dayswhen theAir wascollected. Temperatureexpressed inDegrees of thecentigradeThermometer. State of the Atmosphere. Absorptionproceeding fromthe Inflamma-tion of 200 ofAir and 200 ofHydrogene. Quantityof oxygenecontainedin 100Parts ofAir.
Brumaire 26 ....... 7°.3 Sky overcast; wind E. .......... .... 126,0 .. 21,0 126,0 .. 21,0
27 ........ 4,5 Sky overcast; wind E. S. E. ...... .... 126,0 .. 21,0 126,0 .. 21,0
28 ........ 4,7 Light rains; very high wind S. W. .... 126,0 .. 21,0 126,0 .. 21,0
29 ....... 10,0 Light rain; wind S. ........... .... 126,0 .. 21,0 126,5 .. 21,1
30 ....... 12,5 Sky overcast; wind S. W. ........ .... 126,8 .. 21,2 126,0 .. 21,0
Frimaire 1 ........ 6,7 Sky cloudy, slight rain; wind S. W. .... 126,0 .. 21,0 126,0 .. 21,0
2 ........ 1,5 Cloudy sky; wind W. .......... .... 126,0 .. 21,0 126,0 .. 21,0
3 ........ 8,5 Rain; wind S. ................ .... 126,3 .. 21,0 126,5 .. 21,1
4 ....... 10,6 Sky overcast; wind S. W. ........ .... 126,2 .. 21,0 126,5 .. 21,1
5 ........ 3,3 Cloudy sky; wind E. .......... .... 126,5 .. 21,1 126,0 .. 21,0
6 ...... —1,6 White frost; wind N. .......... ...... 126,0 .. 21,1
7 ...... —1,3 Snow; wind N. ................ ...... 12,65 .. 21,0
10 ...... —4,1 Fog; wind N. N. E. ............ ...... 126,0 .. 21,0
12 ...... —2,8 Cloudy sky, mists; wind E. .... ...... 136,5 .. 20,9
14 ........ 4,2 Rain; wind S. ................ ...... 126,0 .. 21,0
16 ........ 3,1 Thick fog .................... ...... 126,0 .. 21,0
22 ........ 9,6 Rain; wind S. S. W. ............ ...... 126,0 .. 21,0
28 ...... —2,2 Sky overcast; wind N. E. ........ ...... 126,0 .. 21,0
Nivose 2 ........ 1,0 Hoar frost, thick fog; wind S. E. .. ...... 126,0 .. 21,0