Catalysis of the slow combustion of acetaldehyde by alkali halides

Solid alkali halides catalyse the slow combustion of acetaldehyde vapour at 100-125�. The catalysis (by chlorides) is not sensitive to the nature of the cation (Li+, K+, Cs+, Ca2+, Ba2+) but changes drastically with a change in anion, the relative catalytic effects being in the order Br-�Cl- > F-. I- probably exerts an inhibitory effect. The catalysis is attributed tentatively to the sensitizing action of free halogen produced by reaction of acetyl hydroperoxide with the halide. There is a general kinetic similarity with the much weaker catalysis by glass observed by previous workers.