« ZurückWeiter »
Prefent State of the Difpute be-
Account of the Life of Thonias
Chatterton, with Criticisms on
Description of the Country be-
particulars refpecting the Dref-
Account of the introduction of
A wonderful and tragical Rela-
Remarks upon the Prefent Taste
R. Cumberland, Efq.
Prefent State of the Spanish The-
Account of a remarkable Sleep-
to the Phyfical Society of Lau-
ment: By M. Durande,
Anecdotes of the Pretender, La-
In the County of Dumfries, near Drumlanrig. In this house was born the Ad-
State of the L'AROMETER in inches and decimals, and of Farenheit's THER
MOMETER in the open air, taken in the morning before fun-re, and at noon; and the quantity of rain-water fallen, in inches and decimals, from the 31st of Auguft, 1789, to the 29th of Sept. near the foot of Arthur's Seat.
Prefent State of the Dispute between those Chemists who fupport, and those who deny, the Doctrine of Phlogifton
qual to 60 cubic inches, and abfor
2 grains of phofphorus were weighed, fome hours after it was burnt, it had increafed a grain in weight."
Large matches made of linen rags, were dipped in melted brimftone. The quantity of air which was abforbed by the burning match, was 198 cubic inches, equal to th part of the whole air in the veffel."
"I made the fame experiment in a leffer veffel, which contained but 594 cubic inches of air, in which 150 cubic inches were abforbed i. e. full th part of the whole air in the receiver." Exp. 103. Hales therefore had the fame refults from his experiments that we have; for we know that there is about of pure air in atmospheric air.
The fame author found a lighted candle under a receiver, abforb the air and then go out. He found that the remaining air was infected, and could not maintain combuftion. "The candle, fays he, cannot be lighted again in this infected air by a burning glafs.". Exp. 106. He had likewife obferved, as well as other philofophers, that air was abforbed in the process of refpiration.
Thefe experiments were known to all philofophers, and thus M. Lavoifier explains himfelf with regard to them in his Opufcules phyfiques et coymiques. "Hales thewed that air "contributed to the calcination of "metals, and maintained that to it "was owing the increafed weight "of metallic calces. He likewife
T was long known that metals ac
cination; that air was neceffary to the operation, that it was abforbed, and that when the metals were revived, they gave it out again. Ray, Boyle, Hales &c. had obferved this.
"That the fulphureous and acrial particles of the fire, fays Hales, are lodged in many of thofe bodies which it acts upon, and thereby confiderably augments their weight, is very evident in minium or red iead, which is obferved to increafe in weight about th part in undergoing the action of fire; the acquired redne of the minium indicating the addition of plenty oft fulphur in the operation: for fulphur, as it is found to act moft vigorously on light, fo it is apt to reflect the ftrongest, viz. the red And that there is good store of air added to the minium, I found by distilling firft 1922 grains of lead, from whence I obtain ed only 7 cubic inches of air; but from 1922 grains, which was a cubic inch of red lead, there arofe in the like fpace of time 34 cubic inches of air." Veg. Stat. Cap. 6. Exp. 119.
Hales had alfo obferved, that in the combuftion of fulphur, of phofphorus &c. there was an abforption of air, a production of an acid, and an augmentation of weight. Two grains of phofphorus, fays he, Exp. 54. eafily melted at fome diftance from the fire, flamed and filled the retort with white fumes, it abforbed 3 cubic inches of air. A like quantity of phofphorus fired in a large receiver expanded into a space e
"obferved that the phosphorus, or: " rather the pyrophorus of Hom- · T 2 berg,
*Continuation of Metherie's Retrofpective View.
The ancients understood by fulphur what Stahl afterwards called the inflammable principle. But here Hales calls fulphur what Mayer names caufticon, and Scheele she matter of heat.
berg, diminished the volume of "mercurial precipitates I am talk, "the air in which it burned. Heing of are not metallic calces; or "concludes that the air of the at- 66 laftly, that there are calces which. mosphere enters into the compofi- “ may be reduced without the af tion of moft bodies, and exists in "fiftance of phlogiston." And a“them in a folid form, divested of "gain, "The experiments I have its elafticity, and of the greater made oblige me to conclude, that part of the properties we know it in the mercurial calx in question, poffeffes; that this air is in fome "the mercury owed its calciform "measure the band of union in na- "flate, not to the lofs of phlogifton, 66 ture, that it is the cement of all" which it did not fuffer, but to its "bodies, the cause of hardness in "intimate combination with the e"fome, and of weight in others." "laftic fluid, the weight of which, "added to that of the mercury, is "the fecond caufe of the augmen"tation of weight observable in the
Stahl, who was not acquainted with the experiments of Hales, or who difregarded them, never fpeaks
of the action of air on the phenome-precipitates I have examined.”
na which the operations of chemiltry prefented to him; he endeavoured to explain them all by his inflammable principle or phlogifon.
Such was the fate of this branca of science, when Venel, Black, Cavendish, Prieftly, &c. repeated the experiments of Vau Helmont, Boyle, Hales &c. and fhewed that all bodies contained a very great quantity of air, and that atmofpherie air was of prime importance in all the operations of nature.
It was then attempted to reconcile this new doctrine with that of Stahl, and it was faid that in the calcination of metals, the combuftion of fulphur, of phofphorus, &c. the inflammable principle was difengaged, and air abforbed.
But M. Bayen afterwards reduced the calx of mercury, alone and without charcoal, obtaining a quan tity of air, which Dr Prieftly found was pure air. An ounce of red precipitate gave, on different occafions, a volume of elaftic fluid equal to about 40 ounces of water, that is to fay, about 60 cubic inches of air.
Thefe experiments, fays he, throw "light on the matter. I will no "longer hold the language of Stahl's "difciples, who will now either be "forced to confine the doctrine of "phlogiston, or to confefs that the
It is this famous experiment which tho' its author has not been acknowledged, has ferved as the bafis of the new doctrine. What M. Bayen affirmed of mercury has been extended to all the metals, to fulphur, to phofphorus, to charcoal, &c. viz. That their calciform ftate, or combustion, was not owing to the lofs of phlogifton which they did not fuftain, but to their combination with the claftic fluid, (or pure air which Priefly thewed could alone maintain combuftion) the weight of which being added to their own was the caufe of that augmentation of weight obferved by Hales, and others in metallic calces, and in the products of the combuftion of phosphorus or phofphoric acid, &c. Thus we may almost denominate this doctrine the Syftem of M. Bayen.
It could not be explained howe ver by this hypothefis, whence came the inflammable air which was ob tained from a great number of combustible bodies, such as iren, zinc, &c. either by diffolving them in acids, or by expofing them in gunbarrels to fire, or by merely keeping them in water, &c. Recourfe was had to another experiment.
M. Macquer having fet fire to inflammable air under a porcelaine. difh, obtained a good deal of water.
· I repeat:
I repeated the fame experiment with inflammable air, produced by filings of fteel well dried, and expofed to a strong fire in a mall matfrafs. I likewife obtained a quantity of water, and concluded that the water was contained in the air. M. Cavendish drew another conclufion from the fame experiment. He fuppofed that the water obtained was a product of the combuftion of the inflammable air and pure air, and that in general water is compofed of thefe two airs.
From that time the parti fans of the new doctrine, adopting this laft hypothefis, explained, by the decom pofition of water, the origin of all the inflammable air obtained from metals, from charcoal, &c. they like wife profited by an experiment of M. Wart, who had faid that water could be decompofed by iron. Accordingly they contrived to put water into a tube of iron expofed to a white heat, and the inflammable air obtained was owing, according to them, to the decompofition of the water, the pure air of which uniting itfelf to the metal, calcined it. The inflammable air difengaged in the folution of metals in acids proceeds likewife, by this doctrine, from the decompofition of water, &c.
Thus the hypothefis of M. Cavendifh on the conflituent parts of air, coming to fupport the experiment of M. Bayen, has been used to found a new doctrine.
But there till remained a difficulty of fome importance: for tho' metals, fulphur, photphorus, charcoal, &c. abforb pure air in their combuftion and calcination, it did not follow that the principle, whatever it was, which produced the fame and the heat, might not be found in thefe fubftances. Therefore even though they did not contain inflammable air, they might be poffeffed of some other principle, which might be the principle of inflammability.
I was replied to this difficulty by another experiment.
Dr Black, in the year 1757, had faid that all bodies have not the fame fpecific heat. Meffrs Wilke, Wart,
&c. fupported the fame doctrine. At laft Crawford made fome very nice experiments to determine the fpecific heat of bodies. From these it appeared that pure air, of all the bodies that had been made the fubject of experiment, contained the greatest fpecific heat, being to water.
as 87,000 to 1000.
The defenders of the new doct, rine profited by these experiments,. and affirmed that the heat and the flame given out by different combuf tible bodies, did not proceed from: the bodies which poffefed only a fm quantity of fpecific or latent heat, but were owing to pure air,. the specific heat of which is fo con-. fiderable. A body does not burn except when in combination with pure air. This air, lofing its aeriform ftate, parts with the great quan tity of heat it contained, which becoming free, produces the heat and the flame.