<prompt> Fatal close of potassium cyanide is?5 mg10 mg20 mg200 mg  <response>: 200 mg REF: Textbook Of Forensic Medicine and Toxicology: Principles and Practice by Vij page 695 Fatal dose of cyanide: HCN gas - 100-200 ppm in air HCN liquid- 50-60 mg KCN, NaCN- 150-300 mg 200 mg as per Parikh 