Acute aquatic toxicity of protolyzing substances studied as the microtox effect

In tests of acute aquatic toxicity, the effects of protolyzing substances varies with pH. The Microtox toxicity of six chlorophenols was studied over a pH interval and the relation of effects to dissociation was examined. The pKa values of the chlorophenols under the optimal test conditions are presented. The results of the Microtox toxicity tests supported a simple model of two species, phenol and phenate, with different specific toxicity. In five of the six chlorophenols only the effects of the phenol form were observed. The toxicity of the phenol form was 20 times or more higher than that of the phenate.