The technique used for purification of steam volatile water immiscible substance is :

We need to determine the correct purification technique used for a substance that is steam volatile and immiscible with water.

Statement (A): Fractional distillation. Fractional distillation is used to separate a mixture of miscible liquids whose boiling points are close to each other (typically a difference of less than $$25 \text{ K}$$). It relies on repeated vaporization and condensation within a fractionating column. This is FALSE.

Statement (B): Fractional distillation under reduced pressure. This technique (also known as vacuum distillation) is used for purifying liquids that have very high boiling points or those that tend to decompose at or below their normal boiling points. This is FALSE.

Statement (C): Distillation. Simple distillation is used to separate a volatile liquid from non-volatile impurities, or to separate two miscible liquids with a large difference in their boiling points (typically greater than $$25 \text{ K}$$). This is FALSE.

Statement (D): Steam distillation. Steam distillation is a specialized separation process specifically designed for purifying liquids that are steam volatile and completely immiscible with water. Passing steam through the mixture lowers the effective boiling temperature of the organic compound below its normal boiling point, protecting it from thermal decomposition. This matches the criteria perfectly. This is TRUE.

The appropriate technique for a steam volatile, water-immiscible substance is steam distillation.

Answer: Option D — Steam distillation