Part IV. Flame Spectra of Red, Yellow and Green Color Compositions

ABSTRACT: lame spectra of red, yellow and green color  compositions are examined under various conditions.

a. Red Flame

A red flame is produced by bands from strontium (Sr) salts. These bands consist of five main bands [i.e.,  (6013), (6203),  (6300),  (6428) and (6558)], where each number represents the wavelength of the maximum intensity in Angstroms (Å). The influence of chlorine on the  band is quite different from theothers, namely the  band is weakened by chlorine, whereas chlorine intensified the others, and this effect is greater with hydrogen chloride gas than with chlorine gas. This is very clearly observed especially in low temperature flames. The influence of strontium salts is very small. The effect of oxidizers that produce either chlorine or hydrogen chloride gas is quite remarkable. If we add ingredients that have chlorine, they can intensify each band only in high temperature flames. The effects of calcium (Ca) salts were also examined.

b. Yellow Flame

A yellow flame is produced by sodium (Na) salts. The spectrum consists of mainly Na-D lines, but in addition, a continuous spectrum from Na atoms appears between 5,800 and 6,100 Å and makes the flame color rather white, especially at high flame temperatures.

c. Green Flame

Only BaCl bands can produce green flames when barium (Ba) salts are used as the color agents. Compositions without chlorine cannot produce green color because only BaO bands appear, giving white color to the flames. In the presence of chlorine both BaCl and BaO bands appear. The effect of chlorine or hydrogen chloride gas in a flame seem to weaken the BaO bands and to intensify the BaCl bands. The effect of chlorine gas is less than that of hydrogen chloride gas. And so, ammonium perchlorate produces a better green color than potassium perchlorate. Adding some kind of chlorine compound (chlorine donor) is also effective to intensify the green color.

Ref: Selected Pyrotechnic Publication of Dr. Takeo Shimizu, Part 3,  pp 57-86

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