le
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. 2.201 4.966
Carbon monoxide. 1.189 0.006
Oxygen. 2.300 1.430
Marsh gas. 0.072 0.003
Hydrogen. 2.888 0.008
Acetylene. 0.036 Nil.
------- -------
100.000 100.000

The gases leaving the luminous flame show that the diluting action of
the nitrogen is so great that considerable quantities even of the
highly inflammable and rapidly burning hydrogen escape combustion,
while the products of incomplete combustion are present in sufficient
quantity to account perfectly for the deleterious effects of gas
burners in ill-ventilated rooms. The analyses also bring out very
clearly the fact that, although the dilution of coal gas by air in
atmospheric burners is sufficient to prevent the decomposition of the
heavy hydrocarbons with liberation of carbon, and so destroy
luminosity, yet the presence of the extra supply of oxygen does make
the combustion far more perfect, so that the products of incomplete
combustion are h