Preparation of Mohr’s Salt

Mohr’s salt ((NH₄)₂Fe(SO₄)₂·6H₂O), can be prepared through a reaction between ferrous sulfate (FeSO₄) and ammonium sulfate ((NH₄)₂SO₄) in the presence of water. Here’s a simple method for the preparation:

Materials Required

• Ferrous sulfate (FeSO₄·7H₂O)
• Ammonium sulfate ((NH₄)₂SO₄)
• Distilled water
• Glassware (flasks, beakers, stirring rod)
• Heat source

Procedure of Preparation

The steps to prepare Mohr’s Salt is mentioned below:

Step 1: Calculate the necessary quantities of ammonium and ferrous sulfates. These two compounds have a molar ratio of 1:2.

Step 2: Dissolve the measured amount of ferrous sulfate in a suitable volume of distilled water. Stir the solution until the compound is completely dissolved.

Step 3: Similarly, dissolve the measured amount of ammonium sulfate in another container with distilled water. Stir until the ammonium sulfate is fully dissolved.

Step 4: Now, combine the two solutions into a single container, and stir thoroughly. This mixing will lead to the formation of Mohr’s salt.

Step 5: Allow the solution to cool. During cooling, Mohr’s salt will begin to crystallize. The crystals can be separated from the solution through filtration.

Step 6: Wash the crystals with a small amount of cold water to remove any impurities.

Step 7: Dry the crystals by air-drying. Once dried, Mohr’s salt can be stored in a dry place.

Chemical Reaction

The chemical reaction involved in the preparation of Mohr’s Salt is as follows:

FeSO₄ + (NH₄)₂SO₄ + 6H₂O → Fe(NH₄)₂(SO₄)₂.6H₂O

Mohr’s Salt is named after the German chemist Karl Friedrich Mohr, who synthesized it in 1855. In analytical chemistry, Mohr’s salt is frequently used as a primary standard to standardize solutions of other substances, especially when titrating permanganate solutions. In addition, it finds use as a fertilizer in agriculture and various laboratory applications. In this article, we will discuss the various concepts related to Mohr’s Salt.