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).

Date of Award	1979
Original language	English
Awarding Institution	Aston University