Potassium and Sodium Selenocyanate

Potassium selenocyanate serves as a very useful starting material in the synthesis of a variety of organoselenium compounds. Selenocyanates find some use in photographic emulsions, in which they act as sensitizers. 

The potassium salt can be prepared in low yield by fusing a mixture of potassium hexacyanoferrate(II) and selenium. This salt can also be made by dissolving selenium in cold or warm aqueous potassium cyanide. However, this method is troublesome because it is difl cult to crystallize selenocyanates from water without decomposition. The procedure described here yields a very pure product and is easy to carry out even with large amounts of materials.  

Caution. This preparation and the subsequent purification should be carried out under a hood. Canvas or rubber gloves should be worn because the selenocyanate is readily decomposed, with the deposition of red selenium, on coming in contact with the skin. The selenium may be removed by swabbing the skin with dilute aqueous ammonium sulfide. 

A mixture of 210 g. (95 per cent) potassium cyanide and 240 g. commercial gray selenium is melted in a large 

Sodium selenocyanate can be prepared and purified by following the exact procedure outlined above except that a mixture of 200 g. of sodium cyanide and 320 g. of selenium 

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