Potassium thiocyanate is the chemical compound with the molecular formula KSCN.
In a related reaction, KSCN converts cyclohexene oxide to the corresponding episulfide and KOCN.
Dilute aqueous KSCN is occasionally used for moderately realistic blood effects in film and theatre.
When the hands are brought into contact, the solutions react and the effect looks remarkably like stigmata.
This test is not cross sensitive to heroin, methamphetamine, benzocaine, procaine and a number of other drugs but other chemicals could cause false positives.