Potassium hydrogen diphthalate dihydrate: A new structure and correction to the literature

Jason B. Benedict, Theresa Bullard, Werner Kaminsky, Bart Kahr

Research output: Contribution to journalArticlepeer-review


The title compound, K+·[(C8H5O 4H]-·2H2O or K+·- C16H11O8- ·2H2O, was prepared by slow evaporation of an aqueous solution of potassium hydrogen phthalate. The molecular complex consists of a potassium cation coordinated to a proton-bound hydrogen phthalate dimer and two water molecules. The potassium cation resides on a twofold axis in a distorted square-antiprism coordination geometry. The compound is isomorphous with the ammonium analogue, previously misidentified. As potassium hydrogen phthalate is frequently used in the manufacture of buffers, organic carbon standards, acidimetric standards and various other products, the crystallization of a compound with a different stoichiometery from a solution containing the acidimetric standard has important practical implications.

Original languageEnglish (US)
Pages (from-to)m551-m553
JournalActa Crystallographica Section C: Crystal Structure Communications
Issue number11
StatePublished - Nov 2004

ASJC Scopus subject areas

  • General Biochemistry, Genetics and Molecular Biology


Dive into the research topics of 'Potassium hydrogen diphthalate dihydrate: A new structure and correction to the literature'. Together they form a unique fingerprint.

Cite this