Besides being an extremely amusing couple of words to say phthalate phthalate phthalate!, potassium hydrogen phthalate is the primary standard for base titration. To unpack that a bit, potassium hydrogen phtalate is an acidic compound about which we know a great deal. By reacting it to the equivalence point of neutralization (when pH is equivalent to 7.0) with an aqueous base, the base's concentration can be found.

Potassium hydrogen phthalate comes most often as a white crystaline solid which can either be used in concentrated form or diluted in a solution. It has a mole ratio of 204.2 g/mol and a decomposition point of 295C. Frequently shortened to the acronym KHP, potassium hydrogen phthalate has a molecular formula of C8H5O4K.


  __   C 
 // \ / \O--K
|   ||   
 \\_/ \ /O-OH