Dj\ Priestley’s Experiments relating to Phlogiflon , &c. 
399 
Experiments relating to Ph/ogflon. 
THERE arc few fubjecls, perhaps none, that have occa- 
lioned more perplexity to chemifts than that of phlogifton, or 
as it is lometimes called, the principle of inflammability .’ ft 
was the great difeovery of stahl, that this principle, what- 
ever it be, is transferrable from one fubftance to another, how 
different loever m their other properties, fuch as fulphur, wood, 
and all the metals, and therefore is the fame thing in them all. 
But what has given an air of myffery to this fubjeft, has been 
that it was imagined, that this principle, or fubftance, could 
not be exhibited except in combination with other fubftances, 
and could not be made to a {fume leparately either a fluid or 
iolid form. It was alfo afferted by fome, that phlogifton was 
fo far from adding to the weight of bodies, that the addition of 
it made them really lighter than they were before ; on which 
account they chofe to call it the principle of levity . This opi- 
nion had great patrons. 
Ot late it has been the opinion of many celebrated chemifts, 
Mr. lavoisier among others, that the whole dotfrine of phlo- 
gifton had been founded on miftake, and that in all cafes in 
which it was thought that bodies parted with the principle of 
phlogifton, they in fa& loft nothing, but on the contrary, ac- 
quired fomething; and in moll cafes an addition of fome kind 
of air; that a metal, for inftance, was not a combination 
of two things, vrz. an earth and phlogifton, but was probably 
a fimple fubftance in its metallic ftate ; and that the calx is 
produced not by the lofs of phlogifton, or of any thing elfe, 
but by the acquilition of air. 
Vol. LXXIII. G g g The 
