Azides of Nickel

The normal azide, Ni(N3)2, is a green, hygroscopic solid which dissolves readily in water upon standing or heating, hydrolyzed products are precipitated [135]. The compound is extremely sensitive to thermal or mechanical shock [54]. 

Two methods of preparation are known Nickel hydroxide is dissolved in an excess of strong hydrazoic acid to the green solution, alcohol and ether are added to precipitate the azide as a light green, sandy powder [135]. Or, a suspension of nickel carbonate in ethereal hydrazoic acid may be allowed to stand at room temperature for 3-4 days until the suspension is dissolved [54]. 

Upon standing, aqueous solutions of nickel azide separate as green flakes which appear to be mixtures of the normal Ni(N3)2 and the basic (HO)Ni(N3) [62]. The pure basic nickel azide has been established by X-ray studies [160], but its preparation was not described. 

Potassium hexaazidonickelate(II), K4[Ni(N3)e] , is a yellow-green solid which dissolves to some degree in water and is insoluble in alcohol. The salt deflagrates in a flame test but is not sensitive to mechanical shock [161]. It was obtained by mixing solutions of nickel azide and a tenfold excess potassium azide. A solution of nickel azide was first made by dissolving basic nickel carbonate in hydrazoic acid. The green solution, which was 0.2 M with respect to Ni, was then poured into the potassium azide solution (concentration, 25 g KN3 in 100 ml water). Within a week the complex salt separated as a mass of fine crystals that were washed with ice-cold water and alcohol [161]. 

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