Which of the following will act as antiseptic as well as disinfectant?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Phenol
The same substance can act as an antiseptic or a disinfectant depending on its concentration. A 0.2 per cent solution of phenol is an antiseptic (safe on living tissue), while its 1 per cent solution is a disinfectant (for floors, drains, instruments).
Why the other options are incorrect
Option (1) Boric acid — Incorrect. A weak antiseptic used in dilute aqueous solution for eyes; not used as a disinfectant.
Option (2) Iodoform — Incorrect. Used as an antiseptic for wounds; not a disinfectant.
Option (3) Sulphur dioxide — Incorrect. Used in low concentration as a disinfectant (and food preservative), not as an antiseptic on the body.
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Antiseptics and Disinfectants – …
