Assay of Potassium Chloride (Mohr’s Method)

Molecular formula: KCl 

Molecular weight: 74.55 

Principle: It is a direct precipitation titration of potassium chloride with silver nitrate.  Potassium chromate is used as an indicator. At the endpoint, the excess silver nitrate reacts with the indicator to give a brick-red-colored precipitate. 

Preparation of 0.1M AgNO3 solution:  Dissolve 17 gm of silver nitrate in sufficient water and make up a volume of up to 1000 mL with water.  Standardization of 0.1M AgNO3 solution:  Weigh accurately about 0.1 g of sodium chloride, previously dried at 110°C for 2 hours, and dissolved in 5 mL of water. Add 5 mL of acetic acid, 50 mL of methanol, and 0.15 mL of eosin solution. Stir, preferably with a magnetic stirrer, and titrate with the silver nitrate solution.  Store the solution in a well-closed container protected from light. 


NaCl + AgNO3 → AgCl ↓ + NaNO3 

Factor calculation: 

1 Mole of AgNO3 ≅ 1 mole of sodium chloride 

1000 mL of 1M AgNO3 ≅ 58.44 g of NaCl 

1 mL of 0.1 M AgNO3 ≅ 0.005844 g of NaCl

Make sure you also check our other amazing Article on : Assay of Ethosuximide
Sharing Is Caring:

Leave a Comment