Laboratory Preparation of Ammonia gas:

Principle: When finally crushed mixture of dry solid Ammonium Chloride and Calcium Hydroxide (slaked lime) is heated in the ratio of 2:1, the react with each other to release Ammonia gas

\(\rm 2NH_{4}Cl\) + \(\rm Ca(OH)_{2}\) → \(\rm CaCl_{2}\) + \(\rm 2H_{2}O\) + \(\rm 2NH_{3}\)

Requirements:

Apparatus: hard glass test tube, a spirit lamp, a bunsen burner, a delivery tube, a lime tower, a gas jar, corks,  stand and clamp

Chemicals: ammonium chloride(\(\rm NH_{4}Cl\)), calcium hydroxide [\(\rm Ca(OH)_{2}\)]

Procedure

1. A mixture of ammonium Chloride and slaked lime(2:1) is taken in a hard glass test tube.

2. The hard glass test tube is clamped on a stand in an inclined position.

3. A delivery tube is fitted in a cork that is adjusted in the test tube.

4. The free end of the delivery tube is taken in a lime tower filled with quicklime. The quick lime absorbs the moisture.

5. Now the delivery tube is taken in an inverted dry gas are as shown in the figure. Then the test tube is heated gently.

On heating the mixture, ammonia is released from the mixture. The formed materials are passed into the lime tower containing quicklime. The lime tower is used to obtain dry ammonia. The released ammonia is collected by the downward displacement of air in the jar.

Precautions:

1. The apparatus must be made airtight.
2. The hard glass tube should be fixed in an inclined position towards its mouth in order to prevent it from cracking.
3. Heat should be provided uniformly.
4. The gas jar should be dried.