Photochemistry of tetrachlorosalicylanilide and its relevance to the persistent light reactor

The photochemistry of 3,5,3',4'-tetrachlorosalicylanilide has been studied in solution under carefully controlled conditions. When irradiated in a buffered solution of pH 7.4 (physiological pH), three atoms of chlorine are liberated from the molecule instead of one as suggested by earlier photochemical work. From this observation a mechanism is proposed to explain the long-term photobiological effect of this compound in skin i.e. that of the persistent light reactor.