EFFECT OF IRON(III) ON CHEMILUMINESCENCE FROM THE NEUTRALIZATION REACTION OF NITRIC-ACID AND POTASSIUM HYDROXIDE

Low levels (around 90 mu M) of iron(III) caused an increase in chemilu minescence (CL) from the neutralization reaction involving nitric acid and potassium hydroxide without use of any luminescent reagent. When oxygen was excluded from the reaction, a significant decrease in the C L emission was observed. This suggests that molecular oxygen present i n the solutions may play an important role in the process of the iron- catalyzed CL induced by the neutralization reaction, which liberates a sufficient energy. Other experimental parameters like the influence o f several other metal ions, counteranions and acid media were also exa mined. The results showed that the observed CL enhancement by iron(III ) proved to become most remarkable under sporadical conditions alone, and the presence of small amounts (less than 0.20 mM) of sulfate ion i ncrease the catalytic activity of iron(III). A possible mechanism invo lving transient formation of iron-radical complexes upon neutralizatio n and subsequent reaction of the complexes with molecular oxygen is co nsidered for the present CL reaction.