relating to Phlogijlon , . See, Part III. 9 
not poffibly exclude, i ffiould certainly get more acid, when, 
ffiftead of endeavouring to exclude it, I purpofely introduced a 
greater quantity. But the confequence was the production of 
much lefs acid than before, the liquor I procured being fome* 
times not to be diftinguiffied from pure water, except by the 
greateft attention poffible : for though the decompofition was 
made in the fame copper veflei which I ufed in the former 
experiments, there was now no fenfible tinge of green colour 
in it. 
When I repeated this experiment in a glafs veflei, I per- 
ceived, as I imagined, the reafon of the fmall produce of acid 
in thefe new circumfiances : for the veflei was filled with a 
vapour which was not foon condenfed, and being diffufed 
through the phlogifticated air (which is not affeCted by the 
procefs) is drawn away along with it, when the exhaufting of 
the tube is repeated ; whereas, when there is little or no air in 
the veflei befides the two kinds which unite with each other, 
and are decompofed, the acid vapour, having nothing to attach 
itfelf to and fupport it (by being entangled with it) much 
fooner attacks the copper, making the deep green liquor which 
I have deferibed. Sometimes, however, I have procured a 
liquor which was fenfibly green by the decompofition of atmo- 
fpheric and inflammable air, but by no means of fo deep a 
colour, or fo fenfibly acid, as when the dephlogifticated air is 
ufed. 
The extreme volatility of the acid thus formed (and which 
accounts for the efcape of fome part of it in all thefe pro- 
cefles) is apparent from this circumftance, that if the explo- 
fions be made in quick fuccefiion (the tube being exhauflfed 
immediately after each of them, and filled again as foon as 
poffible) no liquor at all will be collected, the whole of the 
Vql. LXXIX. C- acid 
