Preparation:
Chlorinated Lime Prepared by passing chlorine gas through slaked lime (calcium hydroxide):
2Ca(OH)2 + 2Cl2 → Ca(ClO)2 + CaCl2 + 2H2O2
Properties:
White to grayish-white powder with a chlorine-like odor.
Soluble in water, forming a clear solution.
Strong oxidizing and bleaching agent.
Chemical formula: Ca(ClO)₂.
Uses:
As a disinfectant for water purification and swimming pools.
As an antiseptic for wound cleaning in dilute solutions.
Used for disinfecting surfaces in hospitals and households.
Storage:
Store in a cool, dry place away from organic materials and reducing agents.
Keep in a tightly closed, corrosion-resistant container.
Assay of Chlorinated Lime (Calcium Hypochlorite)
Purpose:
To determine the concentration or available chlorine content in chlorinated lime using iodometric titration.
Procedure:
1.Prepare a Standard Solution:
Dissolve a known amount of potassium iodide (KI) in water to create a standard solution.
2.Prepare the Sample:
Weigh an accurate amount of chlorinated lime and dissolve it in a known volume of water.
3.React with KI:
Add a known volume of KI solution to the chlorinated lime solution.
The available chlorine reacts with KI to produce iodine (I₂) and potassium chloride (KCl):
Cl2 + 2KI → I2 + 2KCl
4.Add Indicator:
Add a starch solution as an indicator, which forms a blue-black complex with iodine.
5.Titrate:
Slowly add a standard solution of sodium thiosulfate (Na₂S₂O₃) to the mixture while stirring.
Sodium thiosulfate reduces iodine to iodide:
2S2O32- + I2 → 2I- + S4O62-
The endpoint is reached when the blue-black color disappears, indicating all the iodine has reacted.
6.Calculate Available Chlorine Content:
Measure the volume of sodium thiosulfate used in the titration.
Use the stoichiometry of the reactions to calculate the available chlorine content or purity of the chlorinated lime sample.