the Converfion of cajl into malleable Iron. i 77 
difcharged ; yet, notwithftanding the heat abforbed by its for- 
mation, and that which flows out of the metal in all direc- 
tions, the whole mafs becomes hotter. The oxygene cannot 
be fuppofed to have much fpecific or latent heat, becaufe it 
undoubtedly exifts in the iron in a very condenfed ftate. Neither 
does the appearance of the mafs allow me to afcribe this gene- 
ration of heat to the burning of the inflammable air at the 
furface, as will alfo be immediately evident for another reafon. 
The lefs deep blue colour of the flame at a fubfequent period 
in the operation is probably owing to the abfence of fixed air, 
or at leaft to its being produced more fparingly, the oxygene 
being now nearly confumed. It will not appear furprizing, 
that the oxygene in this cafe Ihould be confumed before the 
charcoal, if it be confidered, 1. that grey iron contains a 
large portion of plumbago ; and, 2. that fixed air contains a much 
larger quantity of oxygene than of charcoal ; near three times 
as much, according to our belt experiments on its formation : 
fo that I afcribe the fubfequent fermentation accompanied with 
the lighter coloured flame almofi: entirely to the converfion of 
the charcoal into an elaftic fluid. A very experienced philofo- 
pher, I am well aware, has aflerted, that water is necefiary to 
this converfion ; an opinion concerning the juftnefs of which 
I have long entertained great doubts. Whenever I have dif- 
tilled charcoal per fe, I have found the firft portions of gas 
to contain fixed air ; an appearance owing, as I believe, to the 
deeompofition of water abforbed from the atmofphere; but, 
after continuing the procefs for fome time, there has ftill been 
a produdion of inflammable air; but from this neither lime- 
water nor milk of lime would abforb any portion, though 
when fired with vital or common air, it would produce fixed 
air ; and if moifture was added to the charcoal, inflammable 
Vol. LXXXI. B b and 
