Question:medium
Which of the following substances acts as both a poison and an antidote?
Which of the following substances acts as both a poison and an antidote?
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Used in gastric lavage for phosphorus poisoning yet toxic itself.
Updated On: Jun 24, 2026
- Copper sulphate (CuSO4)
- Mercuric chloride (HgCl2)
- Arsenic trioxide (As2O3)
- Thallium arsenate
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The Correct Option is A
Solution and Explanation
Step 1: A handful of corrosive metallic salts are dangerous in their own right but find a therapeutic niche against a different toxin. Copper sulphate is the classic example combining both roles.
Step 2: Toxic side: swallowing the blue crystals produces intense stomach burning, repeated vomiting, and at high dose breakdown of red cells, dark urine, abnormal hemoglobin, liver injury and seizures, with fatal outcome from combined kidney and liver shutdown.
Step 3: Antidotal side: during stomach washing for phosphorus ingestion, copper sulphate reacts with the phosphorus to form an inert copper-coated compound, blocking absorption and oxidation of the phosphorus particles.
Step 4: The remaining options, mercuric chloride, arsenic trioxide and thallium arsenate, serve no antidotal purpose and are only poisons.
\[\boxed{\text{Copper sulphate (CuSO}_4\text{)}}\]
Step 2: Toxic side: swallowing the blue crystals produces intense stomach burning, repeated vomiting, and at high dose breakdown of red cells, dark urine, abnormal hemoglobin, liver injury and seizures, with fatal outcome from combined kidney and liver shutdown.
Step 3: Antidotal side: during stomach washing for phosphorus ingestion, copper sulphate reacts with the phosphorus to form an inert copper-coated compound, blocking absorption and oxidation of the phosphorus particles.
Step 4: The remaining options, mercuric chloride, arsenic trioxide and thallium arsenate, serve no antidotal purpose and are only poisons.
\[\boxed{\text{Copper sulphate (CuSO}_4\text{)}}\]
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