41 2 Dr. Priestley’s Experiments relating to Phlogjlon , 
Wood, or charcoal, is even perfectly deffrudtible, that is, 
refolvable into inflammable air, in a good earthern retort, and 
a Ere that would about melt iron. In thefe circumftances, 
after all the fixed air had come over, I have feveral times conti- 
nued theprocefs during a whole day, in all which time inflam- 
mable air has been produced equally, and without any appearance 
of a termination. Nor did I wonder at this, after feeing it 
wholly vanifh into inflammable air in vacuo. A quantity of 
charcoal made from oak, and weighing about an ounce, gene- 
rally gave me about five ounce meafures of inflammable air in 
twelve minutes. 
The fecond article that I fhall now mention affords an in- 
difputable proof of the generation of fixed air from dephlo- 
gifficated air and phlogifton, or inflammable air. I have feve- 
ral times given it as my opinion, that fixed air is a faffiitious 
fibftance , and a modification of the nitrous and vitriolic acids, 
my former experiments greatly favouring that conclufion ; but 
that it was compofed of dephlogifficated air and phlogiffon, 
though maintained by my friend Mr. kirwan, I was far from 
being fatisfied with, till I was forced to confent to his proof of 
it from my own former experiments, and gave him leave to 
mention it, as he has done in his late excellent paper on falts. 
But I have lately had two diredf proofs of it by experiment. 
The firff was when, in repeating a beautiful experiment firft 
made by Dr, ingen-housz, but with fome variation, 1 was 
firing fome (havings of iron in dephlogifficated air confined by 
mercury, by means of a burning lens. In this way I quickly 
fired the iron, and it burned away in a very pleafmg manner. 
But what ftruck me moft was, that, of the air that remained, 
a confiderable portion was fixed air, though in the receiver I had 
nothing but the pureff dephlogifficated air, together with the 
3 iron, 
