The purification of alumina is called

Options

A. Baeyer's process
B. Bosch Process
C. Caster process
D. Hoop's Process.

Explanation

**Step-by-Step Solution:**

1. **Identify the Process**: The purification of alumina is known as Baeyer's process. This is the first step in answering the question.

2. **Understanding the Raw Material**: The raw material used in Baeyer's process is bauxite, which is an ore that contains aluminum oxide (Al2O3) along with impurities.

3. **First Step - Reaction with Sodium Hydroxide**: The bauxite ore is heated with concentrated sodium hydroxide (NaOH) at a temperature of about 150 to 200 degrees Celsius under pressure. This reaction results in the formation of sodium aluminate (NaAlO2).

4. **Second Step - Hydrolysis**: The sodium aluminate solution is then diluted with water and heated to a temperature of 50 to 60 degrees Celsius. During this hydrolysis reaction, aluminum hydroxide (Al(OH)3) is precipitated along with the remaining sodium hydroxide.

5. **Third Step - Calcination**: The aluminum hydroxide obtained is then dried and heated at a temperature of about 1100 degrees Celsius. This process removes water molecules, resulting in the formation of pure alumina (Al2O3).

6. **Conclusion**: Thus, the purification of alumina is called Baeyer's process.