Aniline is purified by

steam distillation

The correct answer is option 1. steam distillation.

Aniline, an aromatic amine, is purified by steam distillation due to its physical and chemical properties. Here’s an explanation of why steam distillation is the preferred method:

Volatility and Boiling Point: Aniline has a relatively high boiling point (184°C) compared to water. Steam distillation allows the distillation to occur at a temperature lower than the boiling point of aniline. By passing steam through the mixture containing aniline, the aniline can vaporize at a lower temperature, reducing the risk of decomposition.

Separation from Non-Volatile Impurities: Many impurities present with aniline may have higher boiling points or are non-volatile. These impurities will not vaporize with the steam and will remain in the distillation flask, effectively separating them from the purified aniline.

Miscibility with Water: Aniline is partially miscible with water, meaning it can form an azeotrope. This allows aniline to be carried over with the steam during distillation, facilitating its separation from less volatile or non-volatile substances

Avoiding High Temperatures: Using steam distillation avoids the need to heat aniline to its boiling point, which can be energy-intensive and potentially hazardous. Lowering the distillation temperature helps in safely handling the purification process.

In summary, steam distillation is effective for purifying aniline because it leverages the compound's volatility at lower temperatures, efficiently separates it from non-volatile impurities, and avoids the high temperatures required for simple distillation.