Ammonium chloride (NH4Cl)

Preparation of Ammonium chloride:

• Ammonium chloride can be prepared by the reaction of ammonia (NH₃) with hydrochloric acid (HCl).
• The chemical reaction is as follows:

NH3 + HCl → NH4Cl

Properties of Ammonium chloride:

• Physical Appearance: White crystalline solid.
• Solubility: Soluble in water and has a cooling, salty taste.
• Nature: Ionic compound.
• Melting Point: 338°C (640°F).
• Chemical Nature: Weak acid, capable of undergoing reactions with bases.

Uses

1. Expectorant: Used in cough medicines to help clear mucus from the respiratory tract.
2. Buffering Agent: Employed in the pharmaceutical industry to maintain the pH of solutions.
3. Fertilizer Production: Used in the production of fertilizers, particularly for rice and wheat cultivation.
4. Industrial Applications: Utilized in electroplating, soldering flux, and metal recovery processes.

Storage

• Conditions: Should be stored in a cool, dry place, away from heat and direct sunlight.
• Container: Keep in a tightly closed container to minimize exposure to air and moisture.
• Avoid Contact: Store away from strong acids, bases, and oxidizing agents to prevent chemical reactions.

Assay (Determination of Concentration/Purity):

Common Method – Acid-Base Titration:

1. Prepare a Standard Solution:

   • Dissolve a known amount of a strong base (e.g., sodium hydroxide, NaOH) in water to create a standard solution of known concentration.

2. Take the NH₄Cl Sample:

   • Accurately weigh a sample of NH₄Cl and dissolve it in a known volume of water.

3. Add an Indicator:

   • Add a pH indicator (e.g., phenolphthalein) to the NH₄Cl solution. The indicator changes color when the solution reaches neutrality.

4. Titrate:

   • Slowly add the NaOH standard solution to the NH₄Cl solution while stirring.
   • The NH₄Cl reacts with NaOH, forming water and ammonium hydroxide (NH₄OH).
   • The endpoint is indicated by the color change of the indicator, signaling the neutralization of the solution.

5. Calculate the Concentration:

   • Measure the volume of NaOH used in the titration.
   • Use the stoichiometry of the reaction and the volume of NaOH to calculate the concentration or purity of the NH₄Cl sample.

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