Electrical Conductivity in Flame Gases with Large Concentrations of Potassium

The conductivity of the hot gases from propane-oxygen flames containing potassium has been measured in a coaxial graphite cell. In the temperature range 1800–2400°K with potassium concentrations of 0.01–1.0% by weight, the measured conductivity agrees with that calculated from the Saha equation and a ``free-path'' kinetic equation. A constant value of 1×10−15 cm2 was used as the cross section for collision between electrons and the combustion products in this calculation. At higher potassium concentrations, up to 7½% by weight, the electron-potassium atom cross section becomes important but a value of about 10−15 cm2 gives fair agreement with the data. At low temperatures and high cell voltages, current saturation resulting from the limited electron emissivity of the graphite was observed.