4f^^ GASES IN THE ATMOSPHERt; 



fiantly prefent ; but in fo fmall proportion as not fo be de- 

 tefled by any left we are acquainted with; it rauft therefore 

 be confounded in the large mafs of azotic gas. 



} . On the xveight of the Oxygenous and Azotic Attnofpheres. 

 VcS^mh/ng the "^'^'"'ous procetTes have been ufcd to determine the quantity 

 oxigen in the of oxygenous gas. 



atmofpheie. j . jhe njixture of nifrous oas and air over water. 



3* With nitrous n r^ r i ■ ' 



gas. -• i^xpoljng the air to liquid fuiphuret of potafh or lime, 



2. withfulphur- with or without agitation. 



3.*Explofion ^' Exploding hydrogen gas and air by elearicily. 



with h.dr.^en. 4. Expotjng the air to a folution of green fulphat or muriat 

 gre?n fu'iphat°of "'^'Z^" '" '^^^^^> Wrongly impregnated with nitrous gas. 

 iron. 5. Burning phofpliorus in the air. 



pho^phoruf. .^" .^" '^^^^ ,''^^'^' ^'^^ ^^>g^" enters into combination and 



AU produce the '^'^s its elafticity ; and if the feveral procetTes be conduded 



famcrcfalt, /kilfully. the refuUs are precifely the lame from all. In ail 



parts of the eartlj and at every feafon of (he year, the bulk 



of any given quantity of atmofpiieric air appears to be reduced 



nearly 21 per cent, by abflraaing its oxygen, Tbis faft, 



indeed, has not been generally admitted till lately; foraQ 



cherpifts having found, as they apprehended, a great difference 



in the quantity of oxygen in the air at different times and 



The oxigen and places; on fome occaOons 20 per cent, and on others 30. and 



azote aie not ^ r /-,,.. ' ." 



variable. ' ^^^^ ^^ oxygen are (aid to have been found. This I have no 



doubt was owing to their not undefflanding the nature of the 

 operation and of the circumflances influencing it. Indeed it 

 is difficult to fee, on any hypothelis, how ^ difproportion of 

 thefetwo elements ffiould ever fubfiff in the atmofpliere. 

 The firft procefs ^^ the ffift of the procelfes above-mentioned has been much 



Th? di'StS' '''^'^'^'^'^^'^ ^^-^^^ ^"^''"'''' ''"'^ ^' '' ^PP^^''^ fr""" '"y ex- 

 is here' perte'a.' P^'^'^"ce to be not only the moff elegant and expeditious of ali 

 ed. the methods hithej-lo ufed, but alfo as corred as any of them, 



when properly conduded, I ffiall, on this occafion, animadvert 



upon it, 



Inftn.aions for U Nifrous gas may be obtained pure by nitric acid diluted 



e proue 5. „,,th an equal bulk of water poured upon copper or mercury ; 



Pure nitrous ^^^'^^ or no artificial heat ffipuld be applied. The laft produft 



'''*• ^^ g^'^ ^'^'=^ "'^y obtained, does not contain any fenfible portioa 



ot azotic gas: at ieaft it may eafily be got with lefs than two 



or three per cent, of (hat gas : It is probably nearly free from 



Citrous oxide alfo, when thus Dbtained. 



^' 



