A I R 



A I R 



diniculiy. liowevcr, of fcparating, by th« only method tlien 

 known, a portion of air from the roll of the atniofphcre, 

 and the necetfai-y iinctrtainty of tlic firll rude attempts to 

 operate upon an invillblc elalHe fnbftance, occafioned the 

 progrcfs of difcovery in this department or chemieal fcience 

 to be iniufnal'.y flow. The following- facls, however, were 

 afcertaincd by Boyle, wliieh, when we confider tlie nume- 

 rous obflacles from bad and imperfect apparatu.? tint he 

 had to contend with, are hii^hly ereditalile to his indiiilry 

 and fagacity. He proved, that the preience of air was 

 ncecifaryto eombuftion and to animal life, by rtiewing, that 

 in the exhaulled rceelvcr flame was almoll; immediately ex- 

 tinguilhed, and various fmall aniij^'als, and even fifli, while 

 in water, were in a fliort time knled : that the fame phe- 

 nomena lake place, but more gradually, in a confined por- 

 tion of atmofpheric air ; and that the death of animals, in 

 this fituation, was not owing to the heated txhahuicnis from 

 their bodies, as was then fnppoied, fmce the (xme eifefts 

 took place when the apparatus was put into a frigorific mix- 

 ture ; he alfo afcertaincd, that animals live longer, crteris 

 pariiius, in a given bulk of condenfed than ot rareiied air. 

 On account of the imperfcAion of his apparatus, he was 

 induced to believe, that no abforption of air took place in 

 relpiration ; and he appears to have had no fufpicion that 

 pure atmofpheric air was a compound fubftance. 



Inunediately after Boyle, fucceeded Mayow, unquefliion- 

 ably tlie greatell chemical genius of that age, but whofe 

 works, by a lingular fatality, excited little or no interefl; 

 among his contemporaries, and were foon totally forgotten. 

 In this itate of unmerited negleft they remained for more 

 than a century ; and it is only within a veiy few years, that 

 the public attention has been diiefted to the writings of a 

 philofopher, who nearly anticipated thofe difeoveries of 

 Prielllev, Lavoificr, and Cavendilli, upon which are baled 

 almolt all the modern improvements in chemillrv. The 

 iirft great improvement of Mayow in the analyfis of atmof- 

 pheric air, was the invention of a proper apparatus ; for this 

 puvpofe, rejefting the ufe of the air-pump, he made choice 

 of glafs jars, inverted in water, as the beil method of con- 

 fining the gafies upon which he experimented. Setting 

 out from the fafis difeovered by Boyle, he argues, that 

 fmce a lighted candle is extinguiflied much fooner in an ex- 

 haulled receiver than in the fame when filled with air, there 

 J.iuft be fomething contrjned in the atmofphere neceflary to 

 the continuance of flame ; and that a candle, in confined air, 

 is not fuffocattd by its own fuliginous exhalations, but dies 

 away for want of an aerial pabulum. The necefTity of air 

 to combuilion is alfo proved, fays he, from the impoffihility of 

 kindling a combultible body in vacuo by the concentrated 

 folar rays, or by any other method. Having eftablilhed this 

 firll poiition, he proceeds to i-ifer, that it is not the whole 

 air but only its more aftive particles, that are capable of 

 fupporting flame, bccaufe a candle goes out in confined air, 

 while yet the greatefl; part of the elaftic fluid remains un- 

 confumed. Alio, fmce fulphur, when mixed with nitre 

 becomes capable of inflammation in vacuo, or even under 

 water, it follows that nitre and atm.ofpherical air contain 

 fome fubltance in common, which he calls Jirc-a'ir parti- 

 cles fparticuU igneo-nere,?..) He next determined the ana- 

 logy between flame and animal life ; and fnewed, that each 

 depended for their continuance on a fupply of fire -air par- 

 ticles : that there was an adlual coufumplion of air in eom- 

 buftion and refpiration he proved, by the rife of water in 

 the jars in which a live animal or a lighted candle was iii- 

 clofcd ; and that the lofs of bulk was owing to the abilrac- 

 tion of fire-air, appeared from the inability of the refidue 

 to fupport animal life. He alfo inferred, that the fire-air 



particles were the heavieft part of atmofpheric air, hccaufe, 



if two mice or two candles were confined in a tall cylmdrical 

 jar, inverted in water, fo as tliat one fhould be near the 

 upper part of the vtlfel, and the other at the bottom, the 

 upper one, whether a candle or animal, would be extinguiflied 

 fome time before the lower one. With regard to tlic pro- 

 portion of lire-air in the atmofphere, he only obferved, that 

 air rendered unfit for combuilion by the breathing of an 

 animal, loil about one fourteenth of its bulk ; at the fame 

 time remarking, that there was probably only a part of the 

 fire-air confumed : he afterwards, indeed, found, that the 

 folution of iron in aquafortis occafioned a diminution of 

 about 25 psr cent, in atmofpheric air ; but though, in this 

 cafe, he produced nitrous gas, and thus abllrafted the 

 oxygen of the atmofphere, yet, as he himfelf draws no con- 

 clufions from it, we fliould rather confider this as an acci- 

 dent than a dilcovery. Mayow never obtained the fire -air 

 of the atmofphere in a feparate Hate, and therefore was un- 

 able to confimi his analyfis of atmofi)lK'ric air by the fyiithc- 

 tical proof ; nevertliekls, he was warranted by a vlit high 

 probability in afilrmlng that the atmofphere confillcd of two 

 k'nds of air, of wliich the igiieo aerial was in the projior- 

 tion of at leall one to 13 ; that it exceeded the other part 

 in its fpecific gravit)-, and was abfolutely eflential to the 

 continuance of flame and animal life. The influence, how« 

 ever, of the prevalent hypotliefis was at that time too 

 ilrong to be fliaken by fober experiment ; and th? labours 

 and very name of Mayow, fliortly funk into oblivion ; the 

 atmofphere was Hill iuppofed to be an undecompofable ele- 

 ment, and its efie(!:l on chemical procefles was very ger.erally 

 overlooked. 



In 1774, exaftly a century after the publication of 

 Mayow's work, the important difcovery xjf dephlogillicated 

 air, by Dr. Prieftley, took place. This philofopher liaving 

 inelofed fome mercurial prcc'iphat^ per J'f, in a jar filled with 

 mercury, and inverted over the fame, procured from it, by 

 means of heat, a quantity of gas, in which a cauvile hurnt 

 witli an enlarged flame, and iucreafed light : the coincidence 

 of this, with the elfecl produced bv dephlogiiiieated nitn-us 

 gas in the fame eircumftances, as liad been already ob;"er\ed by 

 Dr. PiielUey, induced him to beheve that there was fome 

 common principle in nitrous acid and atmofphcrieal air ; and 

 this fufpicion was ftill further confirmed by the difcoverv, 

 that common red precip'iUtte, which is prepared by means of 

 nitrous acid, yielded dephlogiiiieated air in the fame manner 

 as the precipitate /iT yi-. Hence, too, he concluded, that 

 pure atniofpherieal air was not an clement, and that deplilu- 

 gillicated air was that one of its component parts to which 

 the continuance of flame and animal life was entirely owing. 

 Thus we find, both Mayow and Prielllev arriving at the 

 fame general conclufions, tlirough the medium ol entirely 

 different experiments ; the fire-air of the or.c, and the de- 

 phlogiiiieated air of the other, being only two words for 

 tiie fame fubllanee : the experiments of the latter poll'efs, 

 however, this capital fuperiority, that they exhibit in a 

 feparate uncombined ttate, tliat vital part of the atmof- 

 phere, the exillence of which was only to be inferred from 

 thofe of the former. There yet remained, however, for 

 the complete proof of the eompolition of the atmofphere, 

 that a part of it fliould be adlually decompofed, fo as to 

 ftiew its elements feparated ; and then, by their uummi', to 

 recompofe atmofpherical air. This deficiency was fispplled 

 by Lavoilier. pie confined a few ounces of mercuiy and a 

 certain portion of almolphcrical air in a proper glafs appa- 

 ratus, and expofed the mercury for 12 days to a heat nearly 

 equal to that of ebullition ; during this period a part of the 

 mercury was converted mto-a red oxyd, a certain portion vi 

 J N 2 ' ■ ' tile 



