Answer reviewed 27 February 2023
Ammonium thiocyanate is a hygroscopic and deliquescent substance, which means that it can absorb water from the air to the extent that it will dissolve and form a solution. Ammonium thiocyanate has the GHS classifications Acute toxicity Category 4, Eye damage/irritation Category 2, and Harmful long term to the aquatic environment Category 3.1
Ammonium thiocyanate which has liquefied should be stored for collection by a licenced chemical waste disposal contractor. It should remain stored segregated from incompatible chemicals.
You could consider purchasing potassium thiocyanate instead of the ammonium salt for experiments which call for the thiocyanate ion, as the potassium salt is not hygroscopic and therefore has a longer storage timeframe.
We have previously answered related questions which have additional information that you may find helpful:
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Hazardous waste disposal regarding general information
1 ChemSupply Australia website, (2023), Safety Data Sheet: Ammonium thiocyanate. Please search the product information page on the website for the current SDS for ammonium thiocyanate https://shop.chemsupply.com.au/