A young man who drank an industrial cleaning fluid is brought to casualty. There are yellowish-brown stains on his lips, chin and the front of his shirt, and the oral mucosa shows yellowish discolouration. Which acid produces this characteristic staining?

• A Sulphuric acid
• B Hydrochloric acid
• C Acetic acid
• D Nitric acid ✓

Explanation

Nitric acid is a strong oxidising agent that nitrates skin proteins, producing xanthoproteic reaction with a characteristic yellow staining of the skin, lips and mucosa. Sulphuric acid leaves dark brown or black charring, hydrochloric acid leaves greyish-white or brownish marks without yellow tinge, and acetic acid causes superficial burns without pigment change. Yellow staining therefore identifies nitric acid.

Reference: The Essentials of Forensic Medicine and Toxicology, Reddy, 34th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.