The disinfectant value of strongly dissociated mineral acids, such as hydrochloric and sulphuric, depends chiefly upon the number of free hydrogen ions present. The weak organic acids, however, exert a more toxic effect than would be indicated from their degree of dissociation. Kahlenberg and True (1) found that the toxic action of the highly dissociated acids for the plant Lwpinus albus was due to the hydrogen ions. In weakly dissociated acids, they suggested that the undissociated molecule

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... anions may play a role. Of the fatty acid series formic was the most toxic, being strongly dissociated. Propionic, butyric and valerianic exhibited a similar inhibitory activity and were slightly more active than acetic, although this latter acid is more strongly dissociated. The dibasic acids, oxalic, malonic and succinic, decreased in toxicity as the series was ascended. The toxic activity of oxalic was due entirely to the hydrogen ions, as a gram molecule of acid potassium oxalate, which has one half the number of free hydrogen ions as the acid, had the same poisonous effect as half a gram molecule of the acid. Kronig and Paul (2) found that the more dissociated an acid was the greater germicidal action it exhibited against anthrax spores. Exceptions to this relationship existed which they believed were due to the additive action of the anion and undissociated molecule. Clark (3) observed that acetic acid at a dilution which was only two per cent ionized, inhibited the germination of the spores of a group of filamentous fungi, while highly dissociated mineral acids failed to show