Flame regions, separation

Additives may be solid or solutions, or suspensions in a suitable solvent, or liquid. Where solids are employed their particle size is usually of the order of 20 -30 fjtn with direct injection into the combustion space in the vicinity of the burner where pulverised coal or liquid fiiels are employed. For solid fuel combustion on a grate, the additive may be mixed with the fuel prior to combustion or injected in some way to the flame region. Mbdng with the fuel may present difficulties of producing a uniform distribution, particularly for solid fuels. The additive is usually separately applied to avoid these problems. 

Mixtures of NO and NH3 in methane-air flames exhibit separate regions of reducing NO to N2 and then oxidizing NH3 to NO. 

For a very long time, since Faraday if not before, a qualitative conception has been established that the surface of a flame separates the region with oxygen and no fuel (the oxidation region) from the region without oxygen but with fuel (the recovery region). 

If the thermometer has no expansion or contraction chamber, heating the bulb should not be attempted because there is no place into which the liquid may expand to remove bubbles. Occasionally it may be possible to heat the upper region of the liquid along the stem (do not use a direct flame use a hot air gun or steam). Observe carefully, and look for the separated portion to break into small balls on the walls of the capillary. These balls may be rejoined to the rest of the liquid by slowly warming the bulb of the thermometer so that the microdroplets... 

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