»a* On the Quejlion, -whether Azot he 



care. Among thofe whi h he affirms, we ought to confidef 

 the following as his fimcamental one : " When water is 

 boiled in a retort of glafs, or any other material, you obtain 

 azotic gas." The author prefcribes thefe precautions :— 

 ** To obtain azotic gas in the greateft quantity, the water 

 mufl be evaporated only very flowly and by a very gentle 

 heat, which you muft take care not to augment too much,'* 



" It may be obferved in all thefe experiments, without 

 lexception, th^t, when the lad drop of water is evaporated, 

 the azotic gas ceafcs to be produced, though the fire be con- 

 tinued." 



An aflertion fo poiitive induced me to repeat the experi-p 

 nient with the precautions prefcribed by Girianner. It was 

 made with water recently diftilled, and the precipitate from 

 fulphat of alum by potafli well vi^aflied; it was made alfo 

 with very white argil furniflied by Guyton : but though the 

 quantity of water was confiderable, and thefe two experi- 

 ments lafted, therefore, a long time, no gas was difengaged, 

 and the refult was the fame as that of the Dutch chemills. 



It was on this fa6t, however, fo eafy to be afcertained, that 

 Girtanner chiefly eftabliflied the compofition of azot; and 

 hence that of the atmofphcre, " which (fays he) is not, as 

 hitherto believed, a mixture of oxygen gas and azotic gas, 

 but rather a mixture of oxygen gas and hydrogen ; a water 

 )n the form of gas, if I may be allowed the expreflion. When, 

 by chemical experiments called improperly eudio?nelric, the 

 oxyo'cn is feparatcd from the hydrogen, this feparati^yn can 

 never be entirely and completely effefted; a part of the 

 oxygen remains united to the hydrogen, and forms that che- 

 fnical combination which we call azot, and which we obtain 

 in thefe experiments." 



Thus, when we make a mixture of oxygen gas and hy- 

 drogen gas, we form atmofpheric air; and the differences of 

 fpecific gravity, of properties found by all the teds, of pro- 

 ducts in combudion, are only trifling circumdances, to whiph 

 Girtanner pays little attention. 



G. Bouilion-Lagiange, in confequence of Girtanner's me- 

 moir, has made experiments more numerous than mine, but 



J, which 



