air, will be taken from the atmosphere surrounding the burning flame. Such a blue flame does not smoke or deposit free carbon on a cool surface, although if the flame is sufficiently chilled some of the gas will escape unburned.

The action of the mixer is shown in Figure 8. The gas, at pressures above atmospheric air, is forced through a small hole by the pressure in the gas
pipe, and thus acquires a relatively high velocity in passing through the small spud opening. In this way an aspirating or sucking action is produced around the orifice and this draws in atmospheric air from the room so it will mingle with the gas. A gas mixer is, therefore, in effect merely a small air injector. The amount of air going in may be varied by adjusting the air shutter.

The mixer shown is of the type always used on cooking stoves, all hot-water heaters, all incandescent mantle lamps, room heaters of the radiant type, many other room heaters, and all house-heating furnaces or boilers.



If manufactured gas is forced out through a small hole, about the diameter of a pin, enough air can be mixed with the issuing gas to insure

perfect combustion. This is the principle of the yellow or luminous flame burner, as shown in Figure 9. The flames must not be permitted to come in contact with any solid body, because if they do they will deposit carbon and probably produce carbon monoxide. Only very small quantities of manufactured gas can be burned in such burners. In this yellow or luminous type of flame the production of the light is due to the incandescence of momentarily existing carbon particles furnished by the decomposition , by heat, of the gas itself, before coming in contact with the air.

 



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