Blue line on gums seen in which poisoning?
Zinc
Mercury
Phenol
Oxalic acid
Ans. is 'b' i.e., Mercury * Burtonian line is blue line, which is seen on upper gums in lead poisoning.* Similar blue line (but not called burtonian line in these cases) is also seen in poisoning with Mercury (Hg), Copper (Cu), Silver (Ag), bismuth (Bi), and Iron (Fe).
Toxicology