Polyhydroxy-phenol- and Purpurogallin Chemiluminescence

Pyrogallol is transformed by alkaline oxidation to a series of degradation products the most important being pupurogallin and other tropolone derivatives, which are oxidized to fluorescent products. 

The chemiluminescence observed during the oxidation of humic acids is possibly related to pyrogallol or gallic acid oxidation. Humic acids are important soil constituents and the study of their chemiluminescence might be a tool in soil research. The problem here is the still very poorly defined chemical structure of humic acids. 

To reduce the complexity of the problem separate investigations were performed on the oxidation by oxygen or hydrogen peroxide of polyphenols such as pyrogallol, gallic acid and aldehydes, especially formaldehyde. 

Gallic acid is oxidized in aqueous-alkaline solution (pH range 8-12) to a mixture of products fluorescing in the range of 420-700 nm, the maximum being at 470-560 nm. Gallic acid itself exhibits a strong fluorescence maximum at 565 nm [52]. 

As the maximum of the chemiluminescence spectrum is at 640 nm, however, the main emission is ascribed to the transition 

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