Toxicology: opium identification: practice question

A Forensic Medicine question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Forensic Medicine · Toxicology: opium identification

Sample item

A forensic chemist wants to confirm that a brown gummy sample is opium and not pure morphine. Which test is characteristic of opium?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Meconic acid with ferric chloride giving a red colour

Meconic acid is present in opium but not in pure morphine, and it gives a blood-red colour with ferric chloride that is not bleached by dilute hydrochloric acid. Morphine itself is identified by other reactions. The result establishes the sample as opium rather than a morphine alkaloid alone.

Option by option

  • A. Marquis reagent giving a yellow colour

    The Marquis reagent colour reaction is not specific for opium.

  • B. Fehling's test giving a brick-red precipitate

    Fehling's test detects reducing sugars and not meconic acid.

  • C. Meconic acid with ferric chloride giving a red colour (correct)

    Correct. The red meconate complex is specific to opium.

  • D. Bromine water decolourisation

    Bromine water decolourisation is a general test for unsaturation.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Forensic Medicine question

What is the answer to this Forensic Medicine question?

The best answer is C, Meconic acid with ferric chloride giving a red colour. Meconic acid is present in opium but not in pure morphine, and it gives a blood-red colour with ferric chloride that is not bleached by dilute hydrochloric acid.

Why is "Marquis reagent giving a yellow colour" not the answer?

The Marquis reagent colour reaction is not specific for opium.

Why is "Fehling's test giving a brick-red precipitate" not the answer?

Fehling's test detects reducing sugars and not meconic acid.

Why is "Bromine water decolourisation" not the answer?

Bromine water decolourisation is a general test for unsaturation.

What concept does this question test?

It tests Toxicology: opium identification in Forensic Medicine. Morphine itself is identified by other reactions. The result establishes the sample as opium rather than a morphine alkaloid alone.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Toxicology: opium identification?

Learn postmortem changes with their timelines, and toxicology as poison, sign, test and antidote. Then use the flashcards and the other Forensic Medicine questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.