This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Biological Materials & Stains, Subject name: Forensic Medicine
Lee Jones test is used for - 
Select and explain. 
A. Carbolic acid, B. Arsenic, C. Cyanide, D. Lead
C: Cyanide
Answer: C: Cyanide 
Explanation: Ans. is 'c' i.e., Cyanide Lee Jones testo Few crystals of ferrous sulfate is added to 5 ml of the gastric content,o To it, 5 drops of sodium hydroxide is added,o The mixture is boiled and cooled,o To it, 10 drops of 10% hydrochloric acid is added.o Greenish blue colour indicates cyanide and purplish colour indicates salicylate.