Potassium Sulfate - K₂SO₄

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What is Potassium Sulfate?

Potassium Sulfate can be described as an inorganic chemical compound having the chemical formula K2SO4. It can also be referred to as either dipotassium sulfate or Sulfuric acid dipotassium salt. This compound occurs naturally in salt lakes and volcanic lava. Its appearance is as a colourless white crystalline powder or simply crystals. It is purely odourless and has a hard, saline-like and bitter taste. This compound dissolves in water, but it is insoluble in ethanol

production'>Production of Potassium Sulfate

The required steps followed to obtain potassium sulfate are listed as follows.

  • Crushing the langbeinite mineral,

  • Washing the mineral,

  • Extracting it, and

  • Separating

After performing these, the product is treated with the required aqueous solution of potassium chloride to separate the two parts of the double salt from each other. The Potassium sulfate compound can also be produced synthetically, which can be possible by treating the potassium chloride with raw sulfuric acid.

Properties of Potassium Sulfate K2SO4

IUPAC name of K2SO4

Potassium sulfate


2.66 g/cm³

Molecular Weight or Molar Mass

174.259 g/mol

Boiling Point

1,689 °C

Melting Point

1,069 °C

Potassium Sulfate Structure K2SO4

The structure of K2SO4 is represented below.

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Production of Potassium Sulfate

In 1985, there was produced nearly 1.5 million tons of potassium sulfate, typically by the potassium chloride reaction with sulfuric acid, which is analogous to the Mannheim process to produce sodium sulfate. This process involves the intermediate formation of potassium bisulfate, which is an exothermic reaction that takes place at room temperature:

KCl + H2SO4 → HCl + KHSO4

The second step of the process is endothermic, required of the energy input:

KCl + KHSO4 → HCl + K2SO4

Reactions of Potassium Sulfate


Potassium hydrogen sulfate (which is also known as potassium bisulfate), is readily produced by reacting this compound with sulfuric acid. It produces rhombic pyramids that melt at 197 °C (387 °F) and dissolves in 3 parts of water at 0 °C (32 °F). This solution behaves much due to its 2 congeners, H2SO4 and K2SO4, existing in an uncombined manner side-by-side of each other, where an excess of ethanol precipitates normal sulfate (with a little bisulfate) with the excess acid remaining.

The fused dry salt behaviour is similar, and when heated to more than hundred degrees, it acts on titanates, silicates, and so on, similar to the sulfuric acid, heated beyond its natural boiling point does. Thus, it can be used frequently as a disintegrating agent in analytical chemistry.

K2SO4 Uses

  • The dominant use of the potassium sulfate compound can be given as a fertilizer. K2SO4 does not comprise chloride, which can result in harmful to a few of the crops. Potassium sulfate can be preferred for these crops, which include some fruits, vegetables, and tobacco. Crops with less sensitivity can still require potassium sulfate for optimal growth if the respective soil accumulates chloride from irrigation water.

  • The crude salt can also be used occasionally in glass manufacturing. This compound can be used as a flash reducer in artillery propellant charges. It also reduces flareback, muzzle flash, and blast overpressure.

  • Sometimes, it can be used as an alternative blast media same as the soda in soda blasting because it is harder and similarly water-soluble.

  • Potassium sulfate (K2SO4) is also used in pyrotechnics in combination with potassium nitrate to further generate a purple flame.

FAQ (Frequently Asked Questions)

Q1. Explain the Existence of Acid and Base in Potassium Hydrogen Sulfate?

Ans. Let us mix one equivalent of sulfuric acid with one equivalent of potassium hydroxide; the resultant stoichiometric equation can be given as follows.


Here, the base is hydroxide, whereas the acid is sulfuric acid. And, the potassium hydrogen sulfate or potassium bisulfate acts as salt.

Q2. How to Make Potassium Hydroxide from Potassium Sulfate?

Ans. Consider the below chemical equation.

K₂SO₄ + Ca(OH)₂ → CaSO₄(S) + 2KOH(l)

Here, potassium sulfate, which is more abundantly found than most salts, is concentration and temperature-dependent. So, we can recrystallize if the solution is saturated and cool enough. However, this method is defined as a cheaper alternative to Barium, and it is less toxic.

If the formed precipitate has allowed settling for a sufficient time, the potassium hydroxide solution can be drawn off because the filtration can be a laborious and also a painful process.

In addition, the vessel should be capped to prevent the formation of carbonate from the air.

Q3. Give the pH of Dilute Potassium Hydroxide and Explain How it is Stored.

Ans. Potassium hydroxide is a strong base and dissolves readily in water. It is commonly called caustic potash, having a pH of 12. KOH, potassium hydroxide, comes in pellet form. It is very hydrophilic, which means it is more soluble in water. If it is left open to the air, it directly absorbs the water out of the air and eventually forms a concentrated liquid solution, even in the unsealed jar, which is not much convenient anymore. Also, we should keep the KOH solution jar well sealed, for the same reason.

Q4. Explain if Potassium Sulfate is Soluble in Potassium Hydroxide Solutions?

Ans. Potassium hydroxide and Potassium sulfate have almost the same solubility in the water (which is about 120 g/L) at room temperature. Therefore, if the solution of potassium hydroxide is not saturated (which is having less than 120 g KOH /L), it would dissolve the potassium sulfate until saturation.