Theory of Coloured Flame Production

BE Douda Abstract: The theories and attributes associated with the production of colored flames are presented. Particular attention is given to flames containing strontium (red), barium (green), sodium (yellow) and copper (green or blue). Thermal excitation of vaporized neutral atoms, molecules and ions is correlated with the emission of atomic, band and ionic spectra. These spectra are tabulated. The color contribution of C-type chemiluminescence, a non-thermal excitation, is described briefly. The variability of emitters, emissions and color with the operating flame temperature is discussed in relation to the thermodynamic properties of the reactants and the products of combustion. These thermal properties are tabulated. Ionization is shown as a contributor to color degeneration. The use of an ionization buffer to reduce ionization is explained. Depending on flame conditions and the metal being used, the influence of halogens on the production of color is discussed. The influence is not always beneficial. The flame equilibrium shift caused by the halogens is described for each of the metals. Metals and anions other than the halides are discussed in relation to their ability to intensify or suppress emission. The preferred emitters for each of the metals are listed, and idealistic postulates are presented which apply to the production of color in a flame.  
Ref: JPyro 2022 (E)

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