Potassium thiocyanate

Potassium thiocyanate is the potassium salt of thiocyanic acid, with the formula KSCN and a molar mass of approximately 97.18 g/mol. It is supplied as colourless to white crystals that readily absorb moisture from the air. It dissolves in water very easily, and the process is strongly endothermic, so the solution cools noticeably. It is also soluble in polar organic solvents such as ethanol and acetone.

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What is potassium thiocyanate used for?

In analytical chemistry, KSCN is a classic qualitative reagent for iron(III), producing intensely red thiocyanato-iron complexes. It is also used in thiocyanate-based titrations, such as the Volhard method for halides. In biochemistry and molecular biology, the thiocyanate ion acts as a chaotropic agent that disrupts protein structure and hydrogen bonding. In synthesis, it is a source of the thiocyanate group for preparing organic thiocyanates and isothiocyanates. Further applications include textile processing and photographic chemistry.

Which grades and documentation should buyers look for?

KSCN is offered in technical, laboratory and reagent grades, including ACS reagent grade. Purchasers should check the assay, heavy-metal limits, chloride and sulfate content, and iron content, which is particularly critical for colorimetric work. A batch-specific CoA and a current SDS should accompany each delivery. Because the salt is hygroscopic, it should be stored in tightly sealed containers in a dry place.

What are the main safety and regulatory considerations?

Under GHS, potassium thiocyanate is typically classified as harmful if swallowed, in contact with skin or if inhaled. It is also classified as harmful to aquatic life with long-lasting effects. It carries the supplementary EU hazard statement EUH032: contact with acids liberates very toxic gas. It must therefore be kept away from acids and strong oxidising agents. Always confirm the current classification and the supplier's REACH registration status against the SDS.

Related concepts

Related substances and topics include sodium thiocyanate and ammonium thiocyanate, which serve similar roles. Guanidinium thiocyanate is another important chaotropic salt, widely used for nucleic acid extraction. Further related topics are iron(III) chloride, the Volhard titration and the Hofmeister series of ions.