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The mineral form of potassium sulfate, arcanite, is relatively rare. Natural resources of potassium sulfate are minerals abundant in the Stassfurt salt. These are cocrystallizationsof potassium sulfate and sulfates of magnesium calcium and sodium.
Relevant minerals are:
The potassium sulfate can be separated from some ofthese minerals, like kainite, because the corresponding salt is less soluble inwater.
Kieserite, MgSO4·H2O, can be combined with a solution of potassium chloride to produce potassium sulfate.
Potassium – K2O
Sulphur – S
Chloride (as Cl-)
Free Acid as H2SO4
9.5kg/bag 640bags/20fcl 6.08mts/20fcl
Approximately 1.5 million tons were produced in1985,typically by the reaction of potassium chloride with sulfuric acid, analogous to the Leblanc process. Potassium sulfate is produced according to the followingreaction, which is conducted in so-called Mannheim furnaces:
2 KCl + H2SO4 → 2 HCl + K2SO4
The Hargreaves process uses sulfur dioxide, oxygen and water and potassium chloride as the starting materials to produce potassiumsulfate. Hydrochloric acid evaporates. SO2 is produced through theburning of sulfur.
Two crystalline forms are known. Orthorhombic β-K2SO4 is the common form, but itconverts to α-K2SO4 above 583 °C. These structures are complex, although the sulfate adoptsthe typical tetrahedral geometry.
Structure of β-K2SO4.
Coordination sphere of one oftwo types of K+ site.
SO4 environment in β-K2SO4.
It does not form a hydrate, unlike sodium sulfate. The salt crystallize as double six-sided pyramids,classified as rhombic. They are transparent, very hard and have a bitter, saltytaste. The salt is soluble in water, but insoluble in solutions of potassium hydroxide (sp. gr. 1.35), or in absolute ethanol.
The dominant use of potassium sulfate is as a fertilizer. K2SO4 does not contain chloride, which can be harmful to some crops. Potassiumsulfate is preferred for these crops, which include tobacco and some fruits andvegetables. Crops that are less sensitive may still require potassium sulfatefor optimal growth if the soil accumulates chloride from irrigation water.
The crude salt is also used occasionally in themanufacture of glass. Potassium sulfate is also used as a flash reducer in artillery propellant charges. It reduces muzzle flash, flareback and blast overpressure.
It is sometimes used as an alternative blast mediasimilar to soda in soda blasting as it is harder and similarly water-soluble.