Potassium Hydrogen Sulphate crystals 99% Extrapure (CAS 7646-93-7) is a high-purity, white crystalline inorganic compound, also known as potassium bisulfate or potassium acid sulfate. It is a strong acidic salt used as a reagent in chemical synthesis, a food preservative, and in fertilizers, with high solubility in water.Potassium Hydrogen Sulphate crystals of 99% Extrapure grade (also known as potassium bisulfate or potassium acid sulfate) are primarily used as a strong, acidic reagent in analytical chemistry, organic synthesis, and industrial applications. It is a white, deliquescent crystalline powder that acts as a pH regulator and catalyst.