Question

Castor oil is a

• A. Volatile oil
• B. Wax
• C. Oleo-resin
• D. Fixed oil

Hint:

Fixed oils, like castor oil, do not evaporate and are typically derived from seeds.

Answer 1

The Correct Option is D

Castor oil is a triglyceride, mainly of ricinoleic acid, extracted from the seeds of Ricinus communis. It does not evaporate on standing and leaves a permanent greasy translucent mark on paper, unlike a volatile (essential) oil, which evaporates and leaves no residue. It is also not a wax (an ester with a fatty alcohol rather than glycerol) or an oleo-resin (an oil-resin mixture). Because it is a stable glyceride that stays oily at room temperature, it is classed as a fixed oil.

Answer 2

A simple lab test that pharmacognosy students use is the paper-stain test, so let's apply that logic to each option.

1. Volatile oil: A drop of a true volatile oil placed on paper evaporates fully after a while, leaving no permanent mark, since these oils are made of small, evaporable terpenoid/aromatic molecules.
2. Wax: Waxes are generally solid or waxy-soft at ordinary room temperature rather than free-flowing liquids, so they behave quite differently to a liquid oil in this kind of test.
3. Oleo-resin: These are thick, often partly solidifying mixtures of oil and resin, again behaving differently from a clear, free-flowing glyceride oil.
4. Fixed oil: A drop of castor oil placed on paper leaves a permanent, translucent, greasy patch that never disappears, exactly what is expected of a triglyceride fixed oil, because these larger, non-volatile fatty molecules do not evaporate away.

Castor oil's behaviour, permanent stain, liquid at room temperature, glyceride chemistry, matches the fixed oil category precisely.

Therefore, the correct answer is Fixed oil.