Production

The sulphate of potash or potassium sulphate is produced by several processes as follows:

1. Decantation Process or Langbeinite Process. Langbeinite is treated with concentrated solution of potassium chloride to yield precipitates of potassium sulphate.

K2SO4. 2Mg. 2Mg SO4 + 4K Cl = 3K2SO4 = 2MgCl2

The precipitates of potassium sulhate is separated from solution by decantation. As langbeinite is used, the process is termed Langbeinite process, and as decantation is involved in the process, it is also termed decantation process.

Note:  In Lieu of langbeinite, double sulphate of potassium and magnesium may be reacted with potassium chloride to yield potassium sulphate.

2. Glascrite Process. In this process sodium sulphate is reacted with potassium chloride to yield potassium sulphate.

• Na2SO4 + 2K Cl = K2SO4 + 2Nacl

This reaction occurs in two steps as follows:

FIRST STEP

Here, an intermediate compound, glaserite is formed

•  4Na2SO4 + 6KCl = Na2SO4. 3K2SO4 + 6NaCl

Glaserite

SECOND STEP

Here, potassium  chloride reacts with glascrite, to yield potassium sulphate.

• 2KCl + Na2SO4.3K2SO4 = 2Nacl + 4K2SO4

As glascrite is formed as an intermediate compound, this process is termed glaserite process.

3. Mannheim Process.

Sulphuric acid reacts with potassium chloride to yield potassium sulphate.

• H2 SO4 + 2K Cl = K2SO4 + 2HCl

4. Hargreaves Process.

Sulphur is burnt to yield sulphur dioxide

• S + O2 = SO2

Sulphur dioxide is reacted with air (O2), water vapour (H2O) and hot potassium chloride to yield potassium Sulphate.

• SO2 + 1/2O2 + H2O + 2KCl   = K2SO4 + 2HCl

Properties

• Its colour is white
• It is readuly soluble in water
• It contains 41.6 – 44.1% K (Or 50 – 53% K2O). It is usually 90 – 95% K2SO4.
  
• It is a neutral salt and neutral fertilizer.