Potassium sulfate

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Colorless crystals or white powder. Potassium sulfate is used in the manufacture of gypsum cements, fertilizers, alums, and potassium glass. In a closed environment, a saturated solution of potassium sulfate will form an equilibrium at a relative humidity of about 97% (20C).

Chemical structure

Potassium sulfate.jpg

Synonyms and Related Terms

potassium sulphate (Br.); sulfate of potash; sulfate of potass; sal polychrest;


  • Toxic in large amounts by ingestion.
  • ThermoFisher: SDS

Physical and Chemical Properties

  • Soluble in water (pH about 7) and glycerol. Insoluble in ethanol.
  • Deliquescent point at 20C is 97.2 % RH (see saturated salt solutions)
Composition K2SO4
CAS 7778-80-5
Melting Point 1067-1072 C
Density 2.66 g/ml
Molecular Weight mol. wt. = 174.26
Boiling Point 1689 C

Resources and Citations

  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 33
  • Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
  • Susan E. Schur, Conservation Terminology: A review of Past & Current Nomenclature of Materials, Technology and Conservation, Spring (p.34-39); Summer (p.35-38); Fall (p.25-36), 1985
  • The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry 7845

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