<Tr> <Td_colspan="2"> Infobox references </Td> </Tr> <Tr> <Td> </Td> <Td> </Td> </Tr> <P> Potassium hydrogen phthalate, often called simply KHP, is an acidic salt compound . It forms white powder, colorless crystals, a colorless solution, and an ionic solid that is the monopotassium salt of phthalic acid . KHP is slightly acidic, and it is often used as a primary standard for acid - base titrations because it is solid and air - stable, making it easy to weigh accurately . It is not hygroscopic . It is also used as a primary standard for calibrating pH meters because, besides the properties just mentioned, its pH in solution is very stable . It also serves as a thermal standard in thermogravimetric analysis . </P> <P> KHP dissociates completely in water, giving the potassium cation (K) and hydrogen phthalate anion (HP or Hphthalate). As a weak acid hydrogen phthalate reacts reversibly with water to give hydronium (H O) and phthalate ions . </P>

Characteristics of khp that make it qualify as a primary standard