Potassium sulfate

Potassium sulfate (K₂SO₄) (also known as potash of sulfur) is a white crystalline salt soluble in water. It is non-flammable.

The chemical is commonly used in fertilizers, providing both potassium and sulfur.

Potassium sulfate is also a byproduct of the production of nitric acid.

Potassium sulphate, K₂SO₄, a salt known early in the 14th century, and studied by Glauber, Boyle and Tachenius, was styled in the 17th century arcanuni or sal duplicatum, being regarded as a combination of an acid salt with an alkaline salt. It was obtained as a by-product in many chemical reactions, and subsequently used to be extracted from kainite, one of the Stassfurt minerals, but the process is now given up because the salt can be produced cheaply enough from the chloride by decomposing it with sulphuric acid and calcining the residue. To purify the crude product it is dissolved in hot water and the solution filtered and allowed to cool, when the bulk of the dissolved salt crystallizes out with characteristic promptitule. The very beautiful (anhydrous) crystals have the habit of a double six-sided pyramid, but really belong to the rhombic system. They are transparent, very hard and absolutely permanent in the air. They have a bitter, salty taste. The salt is soluble in water, but insoluble in caustic potash of sp. gr. 1.35, and in absolute alcohol. It fuses at 1078. The crude salt is used occasionally in the manufacture of glass. The acid sulphate or bisulphate, KHSO₄, is readily produced by fusing thirteen parts of the powdered normal salt with eight parts of sulphuric acid. It forms rhombic pyramids, which melt at 197. It dissolves in three parts of water of 0 C. The solution behaves pretty much as if its two congeners, K₂SO₄ and H₂SO₄, were present side by side of each other uncombined. An excess of alcohol, in fact, precipitates normal sulphate (with little bisulphate) and free acid remains in solution. Similar is the behaviour of the fused dry salt at a dull red heat; it acts on silicates, titanates, etc., as if it were sulphuric acid raised beyond its natural boiling point. Hence its frequent application in analysis as a disintegrating agent. For the salts of other sulphur acids, see sulphur.