Electron Attachment and Compound Formation in Flames. V. Negative Ion Formation in Flames Containing Chromium and Potassium

Application of several different experimental techniques (flame-ion mass spectrometry, microwave cavity resonance, electrostatic probe, and absorption spectrophotometry) reveals that addition of chromium to fuel-rich atmospheric-pressure H2/O2/N2 flames seeded with potassium results in formation of Cr-containing negative ions. The following reaction scheme, equilibrium constants, and enthalpy changes provide a satisfactory quantitative interpretation of the experimental results: e+HCrO3=CrO3−+H, Δ H0,1°=125± 40 kJ mole−1, H2+CrO3−=HCrO3−+ H, Δ H0,4°=78± 40 kJ mole−1 K1=2500 exp(−13 400/T) K4= 1.7 exp(−9900/T). Electron affinities for HCrO3 and CrO3 inferred from this data are 229 kJ mole−1 and 390 kJ mole−1, respectively.