A burner, promoted by Robert Bunsen,
used widely in laboratories and sometimes in metal heat-treatment. Through
a nozzle at the base is introduced slightly pressurized fuel gas which is
mixed with air (primary air) which the flow induces through adjustable inlets.
The usual gas:air ratio is 1:2. The mixture proceeds up a metal tube, about
13cm (5in) high, and is ignited at the top, giving a flame temperature of
2,000 K. Outer portions of the flame mix with further air (secondary air)
to give a cooler, more luminous flame, where the gas:air ratio is about