Effect of dissolved oxygen levels on oxidative degradation of pyrogallol.

Pyrogallol decomposition in aqueous systems with various dissolved oxygen levels was studied. The reduced dissolved oxygen levels were produced by deaeration via gas permeation. Dissolved oxygen levels were determined using a dropping mercury electrode polarograph. Degradation rates, T90, and relative protection indexes are discussed. Even at dissolved oxygen levels of less than 0.05 ppm, some decomposition of pyrogallol occurred, indicating nonoxidative pathways or the necessity of total removal of dissolved oxygen to afford complete protection. Apparently, reducing the level of dissolved oxygen is a viable alternative to stabilization of aqueous pyrogallol solutions, since the T90 was increased from 1.9 days in water with dissolved oxygen levels of 9.05 ppm to 114.4 days in water with dissolved oxygen levels of less than 0.05 ppm.