Spectrophotometric determination of the thermodynamic pK value of picric acid in water at 25 °C

Abstract

Th e ther modynami c pK value of picric acid was determin ed spectrophotomet l'i cally in wa ter co n ta ining hy droc hl oric acid to re press the io ni zation. The pI(value 0.33 (T< "" 0.46) was obtained from data at 45·0 mIL. A ttempts to determin e t he pI(value by poten t iometric tit r ations of picri c acid and by spectr ophoto metri c m easure ments of picr ic acid solution s in t he n car-saturation ran ge did not y ield satisfactor y res ul ts. The n ew pK va lue is comparcd wit h previously published valucs .