Purity of potassium hydrogen phthalate for use as a pH standard

Abstract

A diethyl ether extraction method is described for the determination, utilising ultraviolet spectrophotometry, of phthalic acid impurity in samples of potassium hydrogen phthalate intended for the preparation of pH standard buffer. The identity or otherwise of samples can be readily shown by a simple e.m.f. technique, as a useful complementary method, thereby obviating the need for certification studies by cells without a liquid junction.