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Potassium hydrogen phthalate, often called simply KHP, is an acidic salt compound. It forms white powder, colourless crystals, a colourless 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.
Minimum Assay: <99.5%
Molecular Formula: C8H5KO4
Molecular Weight: 204.22
Solubility in water (% weight): 80 g/L @ 20 C
Melting Point: 295-300 C
Density (g/cm3): 1.64
Insoluble matter: 0.003%
Loss on drying at 110 C: 0.2%
Chloride (Cl): 0.0015%
Phthalic acid: <0.005%
Sulphate (SO4): 0.003%
Copper (Cu): <0.0004%
Iron (Fe): <0.0005%
Sodium (Na): <0.0099%
Hazard Phrases: Not considered harmful under normal laboratory conditions
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