IIQ ON ATMOSPHERICAL AIR, 



Statical analyfis Facts have obliged me to give a name to common air, which 

 •fair. has been hitherto exclufively applied to the dephlogifiicat«d 



nitrous air of Dr. Prieftly. This remark being made for the 

 fake of perfplcuity, I will endeavour, in the next place, to 

 give a ftatical anal) fis of the atmofpherical fluid. If 100 cubic 

 inches of common air weigh 31 grains, the weight of an equal 

 bulk of azotic gas will be 30.535 grains; becaufe as 1000 : 31 

 : : 985 ; 30.535 ; in like manner the weight of 100 cubic 

 inches of oxigenous gas will be found to be 34.193 grains. 

 The quantity of azotic gas in 100 cubic inches of air, will be 

 flated at 75 inches in the prefent calculation, for the following 

 reafons : Fiiji, Becaufe 75 is the mean of 72 and 78 ; fecond, 

 Becaufe M. Lavoifier found, that four inches of oxigenous 

 gas and 16 inches of air faturate equal quantities of the nitrous 

 gas. Thefe premifes being fettled, we fliall find the weight 

 of 75 inches of azotic gas to be 22.90125 grains; confequently 

 the weight of the oxigen gas in 100 cubic inches of common 

 air, is the excefs of 31 above the lafl number, or 8.09875 

 grains ; therefore as 34.193 : 100 inches : : 8.09875 grains 

 : 23.685 inches, which is the meafure of the oxigen gas in lOQ 

 cubic inches of common air, when the azotic gas is Hated at 

 75 inches. Thus it appears, that if 100 parts of the atmo- 

 fpherical fluid were decompofed, the elementary gafes would 

 occupy together no more than 98.685 fuch parts; and a dif- 

 ference of a like nature will be obferved, if the azotic gas be 

 called 72 or 78 per cent.', hence it follows that the denfity of 

 air is lefs than that of the mechanical mixture of its elements. 

 This pofition may appear paradoxical at the firft view, but 

 chemiflry can furnifli various inflances of compounds, which 

 are fpecifically lighter than the aggregates of their ingre- 

 dients. 

 Theoxigcnof This anal} fis muft remain incomplete, until the powers of 

 the air compared the oxigen of the atmofphere have been compared with the 

 ^'^^ ^^® °*'^^"' correfponding effed of an equal weight of the oxigenous gas. 

 Such an attempt, however, is liable to great uncertainty ; 

 becaufe the experiments which fliould fiipply the necefl^ary 

 data, are varioufly reprefented by different writers. M, 

 Lavoifier fays, that four parts of oxigenous gas and nearly 16 

 of common air, oxigenate equal bulks of nitrous gas, namely 

 17,-|- part?. On the contrary, M. Chaptal found by repeated 

 «xpetiments, that 12, or at ni9ll 13, parts of air were fuffi- 



cient 



