What Is an Antidote for Cyanide Poisoning

The high toxicity of cyanide-containing substances requires the immediate application of a medical antidote. What simple chemical principles dictate both the toxicity of this species and the efficacy of suitable antidotes  

The basis for the toxicological activity of this substance is the reaction of cobalt ion with cyanide ion to form a relatively nontoxic and stable ion complex. The hexacyanocobaltate ion contains a Co2+ central metal ion with six cyanide ions as ligands. This coordination complex involves six coordinate covalent bonds whereby each cyanide ion supplies a pair of electrons to form each covalent bond with the central cobalt ion. The formation constant for the hexacyanocobaltate ion is even larger than for dicobalt EDTA,3 and thus the cobalt ion preferentially exchanges an EDTA ligand for six cyano ligands  

The exchange of EDTA for the CN ion reduces the concentration of cyanide ion in the body, making the cobalt ion an effective scavenger of toxic cyanide ions. 

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