Chemical elements
    Physical Properties
    Chemical Properties
      Potassium hydride
      Potassium fluoride
      Potassium hydrogen fluoride
      Potassium chloride
      Potassium bromide
      Potassium iodide
      Potassium hypochlorite
      Potassium chlorate
      Potassium perchlorate
      Potassium hypobromite
      Potassium bromate
      Potassium perbromate
      Potassium hypoiodite
      Potassium iodate
      Potassium periodate
      Potassium monoxide
      Potassium peroxides
      Potassium hydroxide
      Potassium monosulphide
      Potassium sulphide
      Potassium polysulphides
      Potassium hydrogen sulphide
      Potassium sulphite
      Potassium hydrogen sulphite
      Potassium pyrosulphite
      Potassium sulphate
      Potassium hydrogen sulphate
      Potassium pyrosulphate
      Potassium persulphate
      Potassium thiosulphate
      Potassium dithionate
      Potassium trithionate
      Potassium tetrathionate
      Potassium pentathionate
      Potassium hyposulphite
      Potassium selenides
      Potassium selenate
      Potassium tellurides
      Potassium tellurate
      Potassium nitride
      Potassium hydrazoate
      Potassium hyponitrite
      Potassium nitrite
      Potassium nitrate
      Potassium phosphides
      Potassium hypophosphite
      Potassium orthophosphates
      Potassium pyrophosphate
      Potassium metaphosphate
      Potassium arsenite
      Potassium arsenates
      Potassium carbide
      Potassium carbonate
      Potassium sodium carbonate
      Potassium bicarbonate
      Potassium hydrogen carbonate
      Potassium percarbonate
      Potassium thiocarbonate
      Potassium cyanide
      Potassium thiocyanate
      Potassium silicates
      Potassium fluosilicate
      Potassium silicofluoride
      Potassium hypoborate
      Potassium borates
      Dipotassium tetraborate
      Potassium perborates
      Potassium oxalate
    PDB 1a3w-1dul
    PDB 1dz4-1j95
    PDB 1jbr-1lqp
    PDB 1lrt-1o07
    PDB 1o76-1qb9
    PDB 1qj5-1t86
    PDB 1t87-1vq9
    PDB 1vqk-1yj9
    PDB 1yjn-2aop
    PDB 2apo-2f4v
    PDB 2fbw-2hg9
    PDB 2hh1-2oij
    PDB 2oiy-2uxb
    PDB 2uxc-2x20
    PDB 2x21-3c0y
    PDB 3c0z-3dix
    PDB 3diy-3f5w
    PDB 3f7j-3hqo
    PDB 3hqp-3l01
    PDB 3l0u-3oi5
    PDB 3oia-3r9b
    PDB 3rde-4e6k
    PDB 4edj-8gep

Potassium sulphate, K2SO4

The Potassium sulphate, K2SO4 occurs in nature in the form of double salts. Examples are schonite, K2SO4,MgSO4,6H2O; polyhalite, K2SO4,MgSO4,2CaSO4,2H2O; and glaserite, 3K2SO4,Na2SO4. It is a by-product in the manufacture of nitric acid from potassium nitrate and sulphuric acid, and can also be prepared by the action of sulphuric acid on potassium chloride. The main sources of potassium sulphate are kainite (KCl,MgSO4,3H2O) and sylvine (KCl), both present in the Stassfurt " Abraumsalze." Water decomposes kainite into a sparingly soluble double sulphate of potassium and magnesium, and the very soluble magnesium chloride; a similar product is obtained by the interaction of sylvine and kieserite (MgSO4,H2O). The magnesium chloride is removed by cold water, and the residual double sulphate treated with excess of an aqueous solution of potassium chloride:

K2SO4,MgSO4 + 2KCl = 2K2SO4 + MgCl2.

Potassium sulphate forms white, rhombic crystals, melting-point 1015° C., 1045° C., 1050° C., 1052° C., 1057° C., 1058.9° C., 1066.1° C., 1066.5° C., 1067° C., 1070° C., 1074° C., or 1078° C. Its density is given as 2.6617, 2.6627 at 16.4° C., 2.6633, 2.666, 2.670 at 20° C., and 2.6521 at 60° C. Its specific heat is 0.196 between 13° and 45° C., or 0.1901 between 15° and 98° C. At 1130° C. the vapour-pressure is 0.4 mm. The heat of formation from the elements is given as 344.3 Cal. and 344.6 Cal. The crystals are diamagnetic, and exhibit triboluminescence. The salt does not form hydrates.

Solubility of Potassium Sulphate

The solubility in water is given in the table.

Temperature, °C0102030405060708090100120143170
Grams of K2SO4 in 100 g. of water.7.359.2211.1112.9714.7616.5018.1719.7521.422.824.126.528.832.9

A solution in contact with excess of salt boils at 101.392° C. under a pressure of 760 mm. of mercury. The aqueous solution of the salt has a neutral reaction.
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