The fragrance of flowers is due to the presence of some steam volatile organic compounds called essential oils. These are generally insoluble in water at room temperature but are miscible with water vapour in the vapour phase. A suitable method for the extraction of these oils from the flowers is:

We need to identify the suitable method for extracting essential oils from flowers.

Key Concept: The essential oils are (i) steam-volatile organic compounds, (ii) insoluble in water at room temperature, and (iii) miscible with water vapour in the vapour phase.

Option A: Crystallisation is used for purifying solid compounds, not for extracting volatile oils from plant material, so it is not suitable.

Option B: Distillation under reduced pressure is used for liquids that decompose at or below their boiling points. While it could work for some applications, it is not the standard method for extracting essential oils from flowers.

Option C: Simple distillation separates miscible liquids with significantly different boiling points. Since essential oils are insoluble in water, simple distillation is not the ideal method.

Option D: Steam distillation is the correct method. In steam distillation, steam is passed through the plant material. The essential oils, being volatile, vaporize along with the steam at a temperature below their normal boiling point. The mixed vapours of water and oil are then condensed. Since the oils are immiscible with water at room temperature, the condensed mixture separates into two layers, allowing the essential oil to be easily separated. This method is specifically designed for compounds that are steam-volatile but water-insoluble—exactly matching the properties described in the question.

The correct answer is Option D.