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"The reducing flame (as of a blowpipe) is that part of the flame which is deficient in oxygen for combustion (RF in figure), and which has therefore a reducing effect, or, n other words, tends to deprive the substance under examination of oxygen; the oxidizing flame is that part (OF in figure) in which the oxygen is in excess, and which exerts the opposite or oxidizing effect. The distinction is important in blowpipe analysis." -Whitney, 1911

Reducing and Oxidizing Flames

"The reducing flame (as of a blowpipe) is that part of the flame which is deficient in oxygen for combustion…