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Potassium hydrogen phthalate (KHP) is a white, crystalline, weakly acidic compound commonly used as a primary standard in acid-base titrations. It is the monopotassium salt of phthalic acid and is valued for its high purity, stability, and consistent behavior in analytical chemistry.

🏭⚗️ Production
KHP is synthesized by the neutralization of phthalic acid with potassium hydroxide. The reaction is controlled to ensure only one of the carboxylic acid groups is neutralized, resulting in the monobasic potassium salt. The product is then purified through recrystallization and drying to ensure its suitability for use as a primary standard.

🔬 Properties
The chemical formula of potassium hydrogen phthalate is KHC₈H₄O₄, and its molar mass is approximately 204.22 g/mol. It appears as a white, odorless, crystalline powder. KHP has a melting point around 295 °C (with decomposition) and is sparingly soluble in water but sufficient for titration purposes. It acts as a monoprotic acid in aqueous solutions and provides stable, reproducible pH values in buffer systems.

🧪 Applications
KHP is widely used in analytical chemistry as a primary standard for the standardization of basic solutions, particularly sodium hydroxide. It is also employed in the calibration of pH meters and acid-base titration techniques due to its known and stable molar mass and predictable reactivity. In some cases, it is used in buffer solutions and quality control testing of analytical instruments and reagents.

⚠️ Safety
Potassium hydrogen phthalate is considered safe for laboratory use when handled properly. It may cause mild irritation to the skin, eyes, or respiratory system if inhaled as dust. Standard protective measures such as gloves, goggles, and dust masks are recommended during handling. It should be stored in a tightly sealed container in a cool, dry place away from incompatible substances like strong oxidizers.