The burner has two controls used to adjust the flame.
The Gas Control Needle Valve is used to adjust the
height of the flame.
The needle valve should never be closed completely – it
is a flow control only and can be damaged (the needle gets bent)
if closed completely.
Shut off the gas at the wall/bench (see next page in this module)
to extinguish the burner.
The Air Control Vent is opened by turning the burner tube.
This allows increasing amounts of air to mix with the gas before
combustion, leading to a hotter flame. There are 3 different recognizable
flames:
Cool Yellow flame
a highly visible flame at ~200°C
not used for heating objects because it deposits soot on them
good setting for lighting the burner
a temporarily unused burner should be left at this flame setting
Medium Blue flame
has a uniform blue color
approx. 700 °C
can be hard to see
used for heating solutions/liquids in glass containers (test-tubes,
flasks, beakers)
used when “flame drying” glassware
Roaring Blue flame
has a light blue, triangular inner cone and curved blue outer
cone
hottest spot is just above the tip of the inner cone, >1000°C
region inside the light blue cone is cool, unburned gas
used for direct heating of ceramic crucibles
used for indirect heating of glass beakers and flasks supported
on a wire gauze
not used for direct heating of glass containers as it creates
localized “hot spots” which lead to “bumping”
of solutions and/or cracking of glassware
