Chlorinated Lime (Calcium Hypochlorite, Ca(ClO)₂)

Preparation of Chlorinated Lime:

• Prepared by passing chlorine gas through slaked lime (calcium hydroxide):

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:
     • 2S₂O₃^2- + I₂ → 2I^– + S₄O₆^2-
     • 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.

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