7612. Potassium Biphthalate

Nomenclature

CAS number: 877-24-7
1,2-Benzenedicarboxylic acid potassium salt (1:1); phthalic acid potassium salt; potassium acid phthalate; potassium hydrogen phthalate; acid potassium phthalate.
C8H5KO4; mol wt 204.22.
C 47.05%, H 2.47%, K 19.15%, O 31.34%.

Description and references

Prepd by half-neutralization of a phthalic anhydride soln: F. J. Welcher, Organic Analytical Reagents vol. 2 (Van Nostrand, New York, 1947) pp 75-79. Crystal structure studies: N. G. Furmanova et al., J. Struct. Chem. 35, 697 (1994). Thermal stability studies: E. R. Caley, R. H. Brundin, Anal. Chem. 25, 142 (1953).

Chemical structure

Properties

Orthorhombic crystals, stable in air. d425 1.636. Acid reaction; pH of 0.05M aq soln at 25° = 4.005 (glass electrode). Sol in about 12 parts cold water, 3 parts boiling water; slightly sol in alcohol.

Use

As primary standard for preparing volumetric alkali solns, also as a buffer in pH determinations.