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The anhydrous form is a deep-blue powder; hygroscopic; density 1.872 g/cm³; melts at 280°C; insoluble in water. The dihydrate is pink to reddish brown powder or needles; insoluble in water and acids; soluble in sodium or potassium cyanide solutions, ammonium hydroxide, and hydrochloric acid.

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The compound has limited commercial applications. It is used as a catalyst and in the preparation of cyanide complexes.

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The trihydrate salt is obtained as a reddish brown precipitate by adding potasium cyanide to a cobalt salt solution:
CoCl₂ + KCN + 3H₂O → Co(CN)₂3H₂O + 2KCl
This on dehydration yields anhydrous Co(CN)₂. The Co(CN)₂3H₂O precipitate formed above redissolves when excess KCN is added, forming a red solution of potassium cobalt(II) cyanide, K₄Co(CN)₆. Stoichiomtric amount of KCN should, therefore, be used in the preparation of cobalt(II) cyanide.

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The compound is highly toxic by ingestion and possibly through other routes of exposure.

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