The formation of oxidation ions from aromatics in the presence of small amounts of aliphatic acid may have practical importance for oils in service, since ions are formed even at small concentrations of aromatic compounds. Ions are formed equally in nonpolar and polar solvents. This is shown for tripropionin-hydrocarbon mixtures up to a dielectric constant of about 7.
The ion-forming mechanism during oxidation is inhibited by unsaturated compounds, such as olefins, and also by aliphatic alcohols. The possible causes of alcohol-inhibition are discussed with the aid of absorption spectroscopy in the ultraviolet.
Excessive oxidation reduces ion formation, in agreement with the hypothesis that ions are formed from intermediate oxidation products.