What is potassium hydrogen phthalate?

Potassium hydrogen phthalate, also known as potassium biphthalate or acid potassium phthalate, is a chemical compound with the formula KC8H5O4. It is a white, crystalline solid that is commonly used as a primary standard for acid-base titrations.

Potassium hydrogen phthalate is often used as a standard reference material in analytical chemistry for calibrating pH meters and for standardizing solutions of strong acids. It has a high equivalent weight and is stable in air, making it an ideal substance for precise titrations.

The compound is soluble in water and has a pH of around 4. It can be prepared by neutralizing phthalic acid with potassium hydroxide.

Potassium hydrogen phthalate is also used in the food and beverage industry as a buffering agent and acidulant. It is generally recognized as safe by the FDA when used in accordance with good manufacturing practices.

Overall, potassium hydrogen phthalate is an important chemical compound in analytical chemistry, and it is widely used for its stability and accuracy in acid-base titrations.