
Paris of Water and of Dephlogifiicated Air. 351 
have produced equal quantities of heat*: this matter fhould 
therefore be. put to the teft of experiment, by deflagrating de- 
phlogifticated air with inflammable air of. a known. {pecific 
gravity, or by finding how much dephlogifticated air is necef- 
fary for the combuftion of an ounce of {ulphur, the quantity 
of phlogifton in which has been accurately determined by Mr. 
Kirwan; or by finding the quantity of phlogifton in’ phof- 
phorus, the quantity of dephlogifticated air neceffary for its de- 
compofition being known from Mefi.. Lavoisier and De 1a 
PLAcE’s experiments. 
On confidering thefe latter gentlemen’s experiments on the 
combuftion of charcoal, a difficulty arifes, to know what be- 
came of the remainder of the ounce of charcoal; for the 
dephlogifticated air, in becoming fixed air, gained only the 
weight of 0,3548, or about + of an ounces; about 2 of 
an ounce are therefore unaccounted for. The weight of 
the afhes of an ounce of. charcoal. is very inconfiderable ; + ands 
by fome experiments of Dr. Prisstiey’s, charcoal, when freed 
from fixed air, and other air which it imbibes from the atmof- 
phere, is almoft wholly convertible into phlogifton. The. caufe 
of this apparent lofs of matter, 1 doubt not, thefe gentlemen 
ean explain fatisfactorily, and very probably in fuch a manner 
as will throw other lights on the fubjecé. 
? 
* Orit may arife irom my being miftaken, in fuppofing that the {ame quantity” 
of heat is difengaged by the union of dephlogifticated air with phiogifton, “in the 
form of inflammable air, as is by its union with the phlogifton of phofphorus or, 
fulphur ; and there appears to be fome reafon why there fhould not; becaufe in 
thefe latter cafes the water, being united to the acids, cannot retain fo much ele- 
mentary heat asit can do when left in the form of pure water, which is the cafe 
| when the inflammable air is wled. 
tt 
