Page:Cyclopaedia, Chambers - Supplement, Volume 1.djvu/82

 A I R

A I R

The elafticity of the Air is greatly deftroyed by fulphureous bodies ; and great plenty of Air is united with fulphur in the oil of vegetables. But fulphur in a quiefcent fixed ftatc in a large body, as a roll of brimftone, does not abforb the ehltic Air. And it is to be obferved, that as fulphur thus attracts Air, this fluid will alfo attract fulphur. See Sulphur. Air is found in much greater proportion in the folid parts of vegetables, than in their fluid parts. See Vegetable. Since we find fuch great quantities of elaftic Air, generated in the folution of animal and vegetable fubftances, a good deal muft conftantly arife from the difflblving of thefe elements in the ftomach and bowels, which dilfulution it greatly pro- motes. See Digestion.

The Air is very inftrumental in the production and growth of animals and vegetables, both by invigorating their feveral juices, while in an elaftic active ftatc ; and alfo by greatly contributing in a fixed ftate, to the union and firm con- nection of the feveral conftituent parts of thofe bodies, viz. their water, fait, fulphur, and earth. This band of union, in conjunction with the external Air, is alfo a very powerful agent in the diflblution and corruption of the fame bodies ; for it makes one in every fermenting mixture : now the action and reaction of the ae'real and fulphureous particles, is in many fermenting mixtures fo great as to excite a burning heat, and in others a fudden flame. And it is by the like action and reaction of the fame principles, in fuel and the ambient Air, that common culinary fires are produced and maintained Since then Air is found fo manifeftly to abound in almoft all natural bodies ; fince we find it fo operative and active a principle in every chemical operation; fince its conftituent parts are of fo durable a nature, that the molt violent action of the fire, or fermentation, cannot induce fuch an altera- tion of its texture, as thereby to-difqualify it from refuming, either by the means of fire, or fermentation, its former elaftic ftate, unlefs in the cafe of vitrification, when with the vege- table fait and nitre, in which it is incorporated, fome of it with other chemical principles may, perhaps, be immuta- bly fixt : fince this is the cafe, may we not with good rca- fon adopt this now fixt, now volatile proteus, among the che- mical principles, and that a very active one, as well as acid fulphur ; notwithftanding it has been hitherto over-looked, and rejected by chemifts, as no way entitled to that denomi- nation ? Hales, Veget. Stat. Chap. 6. in fin. See farther of the properties of Air, in the articles Vapour, Fermen- tation, Vegetation, Atmosphere, Lungs, Res- piration, Water, Ice, Sulphur, Fire, bV. The ingenious author fo often cited has given the general name of Air to the fluid arifing from animal, vegetable, and mineral fubftances, by diftillation, fermentation, explofion, as in gun-powder, &c. And tho' his experiments prove this factititious Air to be a permanent elaftic fluid, and to be of the fame weight, and elafticity as the Air we breathe ; yet fome doubt might remain, as to this factitious or artificial Air being entirely the fame with natural Air, and of its being able to ferve the fame purpofes of life in animals. On the contrary, from fome experiments made by Mr. Cotes, and others, it feems that the effects of artificial Air are different from the effects of common Air. Thus in particular, it appeared that artificial Air did not reftore the power of motion to a bee, which had been put into an exhaufted re- ceiver ; yet when file was cxpofed to the open Air, in a little time fhc began to move herfelf : and hence Mr. Cotes Jftif- pects that artificial Air is unfit for the life of animals. This was farther confirmed by an experiment made on two flies included in a receiver, out of which the common Air being exhaufted, fome goofberry Air was made to fupply its place. Afterwards two other flies were included in vacuo, but with this difference, that common Air was reftored to them. The event was, that the latter flics thereby recovered their power of motion, which they had loft in vacuo ; but the former, in the factitious Air, remained irrecoverably dead. It ap- peared likewife by Mr. Cotes's experiments, that artificial Air is not only prejudicial to the life of animals, but to flame alfo. See Cotes, Hydroft. and Pneumat. Lect, 16. Art. 5. Nay, by fome experiments it appears, that factitious Air is a greater enemy to animals, than a vacuum itfelf; and thence the laft quoted excellent author feems to collect, that it kills by fome venomous quality, and not only by the defect of common Air.

But it muft be admitted, with Mr. Hales, that the noxi- ous qualities of factitious Air, whether made by fermen- tation, effcrvefcence, or diftillation, is not a fufficient reafon againfl its being true Air; becaufe it is well known, that commpn Air is frequently alfo impregnated with moft noxious and deadly vapours. Thus the fumes which afcend in the Air from fermenting wines, are very pernicious ; thofe alfo from burning brimftone are moft deadly ; and fuch alfo Mr. Haukf- bee found Air to be, which had paffed thro' heated iron and brafs tubes. But the Air which paffed thro' a heated gjafi tube was not noxious ; an argument that the vapours which arofe from the iron and brafs were noxious, and not the hot Air. And it feems probable that the noxioufnefs of new generated Air, either by fermentation, effervefcence, or fire, as alfo common Air impregnated with the like fumes,.

is principally owing to thofe fumes or vapours, and not to a di- minution of the degrees of its claftiticy j which is the fame in common and in factitious Air. V. Stat. Eff. Vol. 2. p.

We have already mentioned that Air, by being breathed be- comes unfit for refpiration ; and this was proved from feve- ral experiments, made by the refpiration of Air included in bladders. But left any inconvenience might arife from the rancid vapour of bladders, Mr. Hales, contrived to breathe the Air of an Air-pump receiver, by cementing a wooden foflet to it. The refult of the experiment was, that near two gallons of Air, which received no noxious fumes from the receiver ; yet being breathed to and fro for two minutes and an half, became thereby unfit for refpiration. Stat. Eff. Vol. 2. p. 319, 320. See alfo Phil. Tranf. N°. 463. Hence it is no wonder that the Air mould be infected, and apt to breed diftempers in clofe prifons ; where not only the breath, but alfo the plentiful perfpiration of many confined together, ftench the Air, and make it apt to breed what are called goal-diftempers. This inconvenience might in a good meafure be prevented, if goals were fo contrived as to have a free paffage for the wind to blow thro' them, and thereby communicate frefh Air ; for want of which many unhappy perfons are deprived of life.

It has been found that Air which paffed thro* cloths dipped in vinegar, could be breathed to and fro as long again, as the like quantity of Air, which was not thus purified ; fo that the fprinkling the decks of Chips with vinegar may refrefli the Air : and this is confirmed by experience. See Hales, Stat. Eff. Vol. 2. p. 321.

But where the ftench and corruption of the Air is great, vi- negar can be but of little benefit, and that only for a fhort time ; and nothing but a thorough ventilating the Air, can bean effectual cure. See Ventilator. Air which has been breathed becomes moift, as is commonly known; and according to Mr. Hales's computation, the ad- ditional moifturc, to about two gallons of dry Air, by breath- ing it to and fro for two minutes and an half, is not one tenth of its weight. Now this additional moiiture in the Air, does not feem alone fufficient to difqualify it for refpiration ; for common Air has frequently one third, and fomctimes one half of its weight, of moifture in it. And therefore, Air that has been breathed, is not difqualificd merely by additional moif- ture ; but by fome bad quality in that moifture. Mr. Hales fufpedts among others, the groffnefs of the exhalations from the lungs, which may hinder their free entrance into the mi- nute veficles. V. Stat. Eff. Vol. 2. p. 323, 324. The effect of the Air in chemical folutions, is very different in different inftances ; if copper filings be put into afmall quantity of fal armoniac, and two veffels thus prepared, be one of them fet in the exhaufted receiver of an Air-pump, and the other in the free Air ; that in vacuo will be found not to be at all altered, in the fame time in which that in the open Air is become of a fine blue. Hence the free accefs of external Air certainly promotes folution in fome cafes, where it feems to act by encreafing the action of the menftruum. But if another experiment be made, by pouring two ounces- of diftilled vinegar upon two drams of whole crabs eyes in the exhaufted receiver, and at the fame time in another veffel in the open Air ; the ebullition is more violent in vacuo than. in the open Air, and the gage of the Air-pump finks, and fhews that Air has been generated in the conflict, as before- mentioned. And fome of thefe mixtures produce Air in fuch quantities and with fuch violence, as to throw off the re- ceiver of the Air-pump. V. Shaw, Chem. Lectures, p. 50. Some philofophers have fufpected that the Air may become impregnated with lapidefcent falts. Vid. Phil. Tranf. N°. 481- p. 326.

We read of a man dead in appearance, but recovered by dis- tending his lungs with Air ; this was done by blowing into his mouth, and flopping his noftrils. See the cafe in Medic. Eff. Edinb. Vol. 5. Art. 55. or the ahridgm. Vol. 2. p. 399, and alfo p. 240. of Vol. 1.

Air refracts the rays of light, like other fluids, and tranfparent bodies ; and according to Mr. Haukfbee's experiments and computations, the line of incidence in vacuo, is to the line of refraction into common Air, as icoooco to 999736. Haukjb. Phyf. Mech. Exp. p. 225. Smith's Optics in the Rem. Art. 410. See Refraction.

This refractive power of the Air, its trembling motion, and that of the interfperfed vapours, are the caufe of the twink- ling of ftars. See Star. Air inflammable. See the article Damps. AIR-Bl adder, a kind of veficula found in the bodies of fifhes, by means whereof they are enabled to fubftain themfelves in any depth of water, and either to rife or fink therein at plea- fure.

The Air-bladder is the fame with what is otherwife called the fzuim or fwimming-bladder.

The difcovery of the ufe of the Air-bladder took its rife from reflecting, that a bubble of air in rifing from the bottom of a fluid continually dilates till it reaches the top, by rea- fon of the continual diminution of the weight, or prefVure of the incumbent water!. For the air in the bladder, is like the

bubble,