Hydrazinium azide

Hydrazinium azide or hydrazine azide is a chemical compound with formula or. It is a salt of the hydrazinium cation and the azide anion. It can be seen as a derivative of hydrazine and hydrazoic acid. It is an unstable solid.

The compound is of scientific interest because of its high nitrogen content (93% nitrogen by weight) and explosive properties.

Structure
The solid undergoes structural phase transition to a different crystalline arrangement at a pressure of 13 GPa.

Chemistry
Hydrazinium azide decomposes explosively into hydrazine, ammonia, and nitrogen gas:


 * 12 → 3  + 16  + 19

Crystallization with an equimolar amount hydrazine yields the solid hydrazinium azide hydrazinate, ·, or, as monoclinic crystals. This compound is less hygroscopic and less volatile than pure hydrazinium azide. It decomposes explosively into nitrogen, hydrogen, and ammonia.

At pressure of 40 GPa, hydrazinium azide decomposes yielding a linear nitrogen allotrope or N≡$+ N$−$− N$−N=N−$− N$−$+ N$≡N, that decomposes to ε-N2 below 25 GPa.

Reaction of hydrazinium azide with sulfuric acid gives quantitative yields of pure hydrazinediium sulfate and hydrazoic acid:
 * [][] + H2SO4 →  [][] + HN3