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air unfit for respiration, and of producing a peculiar fetid gas, has often been observed in those combinations of fulphur and alcalies, which were formerly called hepars, and which, in the new nomenclature, are termed sulphurets, yet these phenomena have not hitherto been properly connected and explained by a complete theory founded on experiment. This consideration, together with their persuasion of the utility of a more accurate knowlege of the nature of sulphurets, and of their affinity to water, induced them to make these substances the subject of their inquiries.

They first examined the nature of that affinity between the sulphuret and oxygen, in consequence of which the former effects a decomposition of atmospheric air. For this purpose, they confined equal quantities of dry sulphuret of carbonat of pot-ash * in equal volumes of atmospheric air, under two receivers, the one placed over mercury, the other over water, On comparing these two volumes of air by the eudiometer, after they had stood during ten days, it was found that the former, which had been placed over mercury, was not more diminished than common air that had been confined during the same space of time; whereas the latter was so much decomposed as to be very little diminished by the addition of nitrous gas; similar results occurred on repeating the experiment with barytic fulphuret : but, in both these cases, it was observable, that, when the fulphurets were moistened with water, they decomposed the air confined over mercury, as well as that placed over water. The same phenomena were produced on confining these fulphurets with nitrous gas, on which they had no perceptible effect, when perfectly dry: but, when moiftened, they entirely decomposed it, leaving only azotic gas.

From these experiments, and from the sulphat t which was formed by exposing water to the action of sulphuret during its production, and before it could come into contact with the atmosphere, the authors explain the affinity between the fulphuret and oxygen, by observing that, during the formation of the fulphuric acid, or combination of sulphur with oxygen, the alcali presents a base, with which this combination, readily uniting, constitutes a sulphat. The production of the fulphat is, in this case, the effect of two affinities; the one between the sulphur itself and the oxygen, (which, however, does not take place, except in a very high degree of temperature,) and

* Carbonat of pot-ash is che vegetable fixed alcali.

+ Sulphats are vitriolic sales formed by the combination of the vitriolic acid with different bases. Oo2

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the other, from which the former acquires a greater intensity, between the fulphuric acid and the alcaline bale :—but the af. finity between fulphur and oxygen, though increased by the combination of the former with an alcali, is not rendered suffi. ciently intense to act on oxygen in its elastic state, for the sulphuret attracts the oxygen, not of the air, but of the water; probably, because, in the latter, it is combined with less caloric than in its gazous form. A fimilar phenomenon is observable in iron, which, though very little affected by atmospheric air, or even by the purest oxygen gas, greedily attracts the oxygen of water.

Thus it appears, that the immediate decomposition in this case is that, not of air, but of water ; the oxygen of the latter unites with a part of the sulphur, and forms the fulphuric acid, which, by combining with the alcali of the fulphuret, constitutes a fulphat; while the other principle of the water, or hydrogen, as soon as it is disengaged, and before it can assume a gazous form, unites with another part of the fulphur, and conItitutes that elastic fluid known by the appellation of sulphurated hydrogen gas. It is observable, that hydrogen, in its elastic ftate, does not readily unite with sulphur, or, at least, that this combination cannot be effected without a very great degree of heat; for though M. Gingembre affirms, that he produced it by means of the sun's rays collected in the focus of a convex lens, the present writers could not effect it in a red hot glass tube.

The sulphurated hydrogen gas, thus produced, is ro intimately combined with the sulphuret, that it does not separate from this latter on its solution, but remains united with its alcaline base, when this is diffolved in water. Pure hydrogen gas not being soluble in alcalies, it is evident that, to the affi. nity between the sulphur and the alcali, must be ascribed that which is observed between the alcali and the sulphurated hydrogen gas, which is so powerful as to resist the heat even of boil. ing water, and does not yield, except to an acid ; which, in consequence of a stronger elective attraction, faturates the alcali, and thus separates it from the gas :--but the acids, employed for this purpose, ought to be such as do not easily part with their oxygen; for if that be attracted by the fulphurated hydrogen, the acid itself will be decomposed. This is best prevented by diluting the acid with water.

In the alcaline solution of the sulphurated hydrogen gas, the latter retains its peculiar properties, particularly that of forming water by separating from the sulphur and combining with oxygen gas : but it must be observed, that this folution will not take place, unless the alcali itself be diffolved in water. It may be added, that this property of being absorbed by alcalies, affords a criterion by which sulphurated hydrogen gas may be distinguished from the other kinds of inflammable air, as the carbonated and phosphorated, which have not this affi nity, and suggests an easy method of separating it from other species of gas, with which it may happen to be mixed.

On introducing ammoniacal gas into a receiver, placed over mercury, and containing an equal quantity of sulphurated hydrogen gas, the volume of the mixture diminished considerably, a white vapour arose, and a blackish powder was de. posited on the surface of the mercury, after standing till the vapour had subsided, the gas was transfused into a clean re. ceiver, and placed over pure mercury; diluted sulphuric acid being added to this, the gas was entirely absorbed, which shewed that it was ammoniacal: but the same acid being introduced into the receiver in which the mixture had been made, and which now contained only what had been deposited by the vapour, the sulphurated hydrogenous gas was reproduced, and in a volume equal to that which it had filled previously to the mixture.

This experiment illustrates the affinity between alcalies and sulphurated hydrogen gas, which seems hitherto to have been to little observed, that M. Fourcroy, in his Elements of Chemistry, denies it. It also shews that, when the ammoniacal and sulphurated hydrogen gas unite, they both quit their elastic ftate, and form a species of ammoniacal sulphuret, or, at least, a combination which has this property of a sulphuret, that sulphurated hydrogen gas may be produced from it by the addition of an acid, though not by heat.

From the preceding facts and observations, it appears that a solution of an alcaline sulphuret in water may be considered as resolvable into the three following principles: the sulphuret itfelf, or the combination of sulphur with the alcali; the fulphat, formed by the decomposition of the water, and the union of its oxygen with a part of the fulphur; and, lastly, the sulphurated hydrogen gas diffolved in the alcaline base of the fulphuret. It is entirely to the last of these, which absorbs the oxygen gas, that the decompofition of atmospheric air, when confined with an alcaline fulphuret, must be ascribed.

When the solution of the fulphuret in water is performed in vefsels accurately closed, the decomposition of the water continues no longer than till its alcaline base is saturated with fulphurated hydrogen gas. Thus sulphurets may be preserved, that is, they will not be entirely transformed into sulphats,-in bottles closely stopped :-whence it may likewise be concluded, that the decomposition of water by fulphurets, though partly

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occasioned by the affinity between the alcali and the fulphuric acid, is also promoted by that between the alcali and the fulphurated hydrogen gas; and this may perhaps be one reason why sulphurets decompose water rather than atmospheric air : for if a Auid fulphuret be confined in the latter, the hydrogen attracting the oxygen produces water, while the fulphur, with which the hydrogen had been combined, remains dissolved in the alcali: but the water, thus generated, is afterward decomposed and reproduced alternately, till, at length, the sulphuret is entirely transformed into a fulphat.

Such are the principal facts and observations contained in this ingenious and interesting memoir, which we are the more desirous of communicating to our readers, because it is now printed, not for sale, but only to be distributed among the philosophical friends and correspondents of the authors. It will be, or perhaps already is, published in the Journal Physique: but many of our chemical readers may not have an opportunity of consulting that work.

CIETY

Art. X. Verhandelingen raakende den Natuurlyken en Geopenbaarden

Godsdienfi, &c. i.e. Prize Dissertations relative to Natural and Revealed Religion; published by TEYLER'S THEOLOGICAL SO.

Vol. XII. 4to. pp. 512. Haarlem. 1792. There here is not, perhaps, in the whole range of theological in

quiry, a question of greater importance than that which is discussed in the volume before us. With respect to religion, as to every other subject proposed to the human mind, men are apt to run into extremes, which, however opposite to each other, are equally injurious to the cause of truth. Some pious and well-meaning persons have unfortunately confounded the history of revelation with revelation itself; by too indiscriminate an affertion that the Bible is literally the word of God, every part of which is alike the result of an immediate divine inspiration, they have exposed Chriftianity to many objections; and have thus, unintentionally, given occasion to the most plausible reasons for infidelity. Others have deviated into a contrary error, and, by too great a latitude in explaining the words of the sacred writers, have given occasion to depreciate the fanctity of their character, and have weakened their authority, both as the historians and as the preachers of the goipele Truth, as is generally the case, seems to lie between the two opposite extremes; and it was to promote the discovery of this happy medium, that the truly respectable directors of TEYLER'S THEOLOGICAL Society submitted the following proposition to the discussion of liberal and rational Christians :

Did not Chrif in his discourses, and the Evangelists and Apostles in their writings, sometimes accommodate their expreffions and arguments to the popular notions then prevalent? ' if , in what particular instances, and how far, did they act thus? Of what ufe is this hypothesis, well defined and rightly apprehended, in explaining the scriptures of the New Testament?

Two differtations on this interesting subject are here published; the one written by the Rev. Paul Van Hemert, Profeffor of Philosophy and Literature in the Society of Remonstrants in Amsterdam, to whom the gold medal was awarded; the other by the Rev. William De Vos, Minister of the Baptift congregation in the same city, to whom a filver medal was decreed.

After some general observations on the importance of the question, Professor Van HEMERT proposes to divide his inquiry into three parts, corresponding with those of the propofition. The first chapter he introduces by defining popular notions, as the term is stated in the question, to be those opinions, either of the people in general, or of particular fects among them, which, though they may be in some measure connected with their religious sentiments, are in themselves inconsistent with the nature of things; the propofition itself implies, that the opinions mentioned are erroneous, and that the person who accommodates his discourse to them, knows them to be such, but does not think it advisable to oppose them; he may acquiesce in such erroneous notions eitier indirectly, by forbearing to contradict them when an opportunity offers of so doing; or else directly; and this either by making use of such expresfions as are founded on them, or by seeming to adopt the notions themselves, and adapting his mode of reasoning to them. After settling these preliminaries, our author examines those sources whence we may derive a knowlege of the popular notions which prevailed among both Jews and heathens, at the time of our Saviour's appearance on earth. Here we find some excellent observations on the Talmud and the Rabbini. cal writings, as well as on the works of Josephus and Philo. The Profeffor then thews the absolute necessity that Christ and his apostles should adapt their discourses to the capacities and circumstances of the people, by making use of the common popular expressions and allusions; hence they acquiesced in the vulgar notions relative to the phenomena of nature, however erroneous and unphilosophical they might be. Remarkable instances of this fact occur in the epistle to the Galatians, iii. 1. in which the apostle asks them, who had bewitched them; and in Acts, xvi. 16. where a damsel is said to be poffeffed with a spirit of Python or Apollo. Thus far most Christians will

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