Potassium bisulfate

Natural Occurrence

Mercallite, the mineralogical form of potassium bisulfate, occurs very rarely. Misenite is another, more complex, form of potassium bisulfate.

Preparation

Potassium bisulfate is prepared by neutralizing sulfuric acid with an equal molar amount of a potassium containing base, for example potassium hydroxide:

Potassium bisulfate is also formed by the union of sulfuric acid with potassium sulfate:

Potassium bisulfate is also the main by-product in the production of nitric acid from potassium nitrate and sulfuric acid:

Chemical Properties

Thermal decomposition of potassium bisulfate forms potassium pyrosulfate and water:

Temperatures above 600 °C further decompose potassium bisulfate to potassium sulfate and sulfur trioxide:

Aqueous solutions of potassium bisulfate behave as two separate, uncombined compounds, K₂SO₄ and H₂SO₄. Adding ethanol to the solution precipitates out potassium sulfate.

Uses

Potassium bisulfate is commonly used to prepare potassium bitartrate for winemaking. Potassium bisulfate is also used as a disintegrating agent in analytical chemistry or as a precursor to prepare potassium persulfate, a powerful oxidizing agent.