Potassium ferrocyanide  -  K4Fe(CN)63H2O

 

 

Potassium ferrocyanide, also called potassium hexacyanoferrate (II) is a common compound. Although this compound contains cyanide groups, it is only marginally toxic. The cyanide groups are coordinated to the iron very tightly and are released only on strong heating, strong UV-radiation or in fairly concentrated acids.