Picric acid in aqueous solution

Abstract

Conductance measurements at 25° indicate that picric acid behaves as a simple monobasic acid (pK=–0·327) only in very dilute aqueous solution, and that some association equilibrium is established with rising concentration. This effect, with special experimental difficulties, is believed to invalidate previous pK values obtained by conductance. New observations of visible and ultraviolet light absorption provide further evidence of complexity which discounts the spectrophotometric method of pK evaluation. The abnormal behaviour of picric acid in aqueous solution is discussed.