Potassium hydrogen phthalate is commonly used as a primary standard to standardize sodium hydroxide solutions. The usual procedure is to weigh a dried sample of primary standard grade KHPhthalate dissolve it in DI water and titrate with base solution to a phenolphthalein end point. Using the base as the titrant minimizes exposure to CO2 in the air and it is easier to see the appearance of the pink indicator than its disappearance. Of course an electromeric titration using a pH electrode doesn't need an indicator.