Potassium thiocyanate

Uses

Chemical synthesis

Aqueous KSCN reacts almost quantitatively with Pb(NO3)2 to give Pb(SCN)2, which has been used to convert acyl chlorides to isothiocyanates.

KSCN converts ethylene carbonate to ethylene sulfide. For this purpose, the KSCN is first melted under vacuum to remove water. In a related reaction, KSCN converts cyclohexene oxide to the corresponding episulfide and KOCN.

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KSCN is also the starting product for the synthesis of carbonyl sulfide.

Special effects

Dilute aqueous KSCN is occasionally used for moderately realistic blood effects in film and theatre. It can be painted onto a surface or kept as a colorless solution. When in contact with ferric chloride solution (or other solutions containing Fe3+), the product of the reaction is a solution with a blood red colour, due to the formation of the thiocyanatoiron complex ion. Thus this chemical is often used to create the effect of 'stigmata'. Because both solutions are colorless, they can be placed separately on each hand. When the hands are brought into contact, the solutions react and the effect looks remarkably like stigmata.

Laboratory

The reaction with Fe3+ mentioned above is used as a test for Fe3+ ions in the laboratory.

Law enforcement

Approximate cocaine purity can be determined using 1 mL 2% cupric sulphate pentahydrate in dilute HCl, 1 mL 2% potassium thiocyanate and 2 mL of chloroform. The shade of brown shown by the chloroform is proportional to the cocaine content. This test is not cross sensitive to heroin, methamphetamine, benzocaine, procaine and a number of other drugs but other chemicals could cause false positives.

References

References

1. "Potassium thiocyanate [NF]".
2. Smith, P. A. S.. (1973). "2a-Thiohomophthalimide".
3. Searles, S.. (1973). "Ethylenesulfide".
4. van Tamelen, E. E.. (1963). "Cyclohexenesulfide".
5. (1 April 1983). "Semiquantitative screening test for cocaine". Analytical Chemistry.