Potassium thiocyanate, KCNS

The Potassium thiocyanate, KCNS, is formed by fusing potassium cyanide with sulphur, or a mixture of potassium ferrocyanide and potassium carbonate with the same reagent. The colourless, deliquescent crystals melt1 at 161.2° or 172.3° C., their density being 1.886. At 430° C. the salt develops a blue colour, but becomes white again on cooling. The heat of formation from the elements is 50.5 Cal., and at 20° C. the solubility is 217 grams per 100 grams of water. Sulphur dioxide reacts with it in aqueous solution to form a complex derivative. Sodium hypobromite reacts energetically with potassium thiocyanate, evolving heat and forming potassium cyanate and sulphate.