Ionisation in Flames with Additives

Abstract

The addition of phosphorus to a series at atmospheric pressure, of alkalimetal-seeded H2/02/N2 flames results in the formation of negative ions accompanied by a decrease in free electron concentrations. Observations were made of the effects of phosphorus on the ionisation of sodium, potassium, rubidium and caesium. The ionisation of lithium is reduced by extensive hydroxide formation, and was too small for accurate measurements. The construction of the measuring system is described, together with a discussion of the principles involved in its use. The concentrations of electrons, positive ions and hydrogen atoms, have been measured using the microwave resonant cavity, the rotating electrostatic probe and the spectrophotometer, respectively, to investigate the effect of phosphorus on both the charged and the neutral species. Phosphorus has been introduced as dimethylphosphite. - These flames collectively span a temperature range from 2000°K to 2500°K. Temperatures have been measured by the sodiumline reversal technique. From the results obtained, it has been shown that phosphorus raises the degree of ionisation of alkali metals which is the reason of increasing the positive ion concentration uniformly as the partial pressure of phosphorus increases and at sufficiently high values of total phosphorus, the electron concentration decreases. The concentration of electrons is linearly proportional to the concentration of hydrogen atoms which decreases as height increases. The electron affinity of PO2, has been obtained throughout the course of this work. (E.A. of PO2 = 3.1 eV).