I have, however, long doubted this
fact, and at length, by a delicate process of analysis have been able
to confirm my suspicions. The outer zone of a luminous flame is not
the zone of complete combustion; it is a zone in which luminosity is
destroyed in exactly the same way that it is destroyed in the Bunsen
burner; that is the air penetrating the flame so dilutes and cools
down the outer layer of incandescent gas that it is rendered
non-luminous, while some of the gas sinks below the point at which it
is capable of burning, with the result that considerable quantities of
the products of incomplete combustion carbon monoxide and acetylene
escape into the air, and render it actively injurious.
I have proved this by taking a small platinum pipe, with a circular
loop on the end, the interior of the loop being pierced with minute
holes, and by making a circular flame burn within the loop so that the
non-luminous zone of the flame just touched the inside of the loop,
and then by aspiration so gentle as not to distort the shape of the
flame, withdrawing the gases escaping from the outer zone. On
analyzing these by a delicate process, which will be described
elsewhere, I arrived at the following results:
GASES ESCAPING FROM THE OUTER ZONE OF FLAME.
Luminous. Bunsen.
Nitrogen. 76.612 80.242
Water vapor. 14.702 13.345
Carbon dioxide.
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