COLLECTION OF MEMOIRS. OOf 



Toail has re-appeared under I he name of acidum pingue, igneous 

 Bcid, and under feveral other denominations which it would 

 'be fuperfluous to enumerate. 



Staahl could not be ignorant of the fadl that metals expofed — and of Staahl» 

 k> heat acquire an increafe of weight ; and yet he not only did 

 not attempt to explain it, but alfo the fyftem under which he 

 clafled the whole of the chemical pfhenomena, and which after 

 liim has been fo much exiended, is ahfdlutely in .contraclidtiou 

 with this capital fa<5l. 



Staahl fuppofed that the metals are compofed ©f a inetanie 

 -earth, and an inflammable principle, which he named phlogi- 

 ilon; he pretended that they loft this principle by their oxida- 

 lion, and that they could not return to the metallic ftate unlefs 

 the phlogifton they had loft was reftored to them. 



It was difficult to imagine how the metals acquired weight, Blfficukles af 

 whim, according to Staahl's doarine, they loft a part of their f ^^'°**'*^' 

 "Tubftance; and on the other hand, how they diminidied in 

 weight, when they recovered one of the principles which 

 they had loft ; it was one of the chief difficulties that could be 

 ■propofed againft the theory of Staahl, this difficulty however, 

 has not ifcindered the theory from having a fuccefe of limited 

 duration. 



Guyton Morveau has made fame unfuccefrful efForis to pal- Morvcau's en- 

 ^iate thiscontradiaion, in his difTertation on this fubjea, under J^^^'JJ^^^ "* 

 the title of Degreffiom Acadeniiques ; hefuppofes that phlogi- 

 ilon is lighter than atmoipheric air ; and he concludes that all 

 bodies -that acquire phlogi-fton ftmuld lofea part of their weight; 

 that, on the -contrary, thofe which lofe phlogifton fliould aug- 

 ment in v»reight. This CKpIanation would have been tenable^ 

 liad the augmerrtation of weight acquired by the metallic ox- 

 ides been equal only to the weight of the air dilplaced ; or, 

 which is the fame things if it had difapp.eared on weighing ia 

 -vacuo ; but the augmentation is much too confiderable to ad- 

 mit of being attributed to that caufe, fince in fome metals it 

 exceeds one third of their weight. It is ncceffary then, either 

 ■to give up the explanation of Guyton Morveau, or to fuppofe 

 that phlogifton has a negative gravity, a tendency to recede 

 ^firom the centre of the earth, a fuppofition incompeiLxble with 

 all the faas admitted by the difciples of Staahl. 



Such was the ftate of the I'cience when a fct of experinvents Hlftory of the 

 tindertaken in 1772, upon the different kinds of air or gas ^°" '*^"*'' 

 Ga which 



