Preparation of alkali-metal azides

In a process for the preparation and purification of alkali-metal azide by contacting with water a dilute two component slurry having a solid insoluble component of alkali-metal azide/alkali-metal hydroxide double salt and a single phase liquid component consisting essentially of substantially anhydrous liquid ammonia to effect solution of at least a portion of said azide double salt and thereafter separating alkali-metal azide from the resultant solution;

• the improvement which comprises:
• settling from said dilute slurry a layer of said double salt having a double salt concentration greater than said dilute slurry, separating said settled layer from supernatant slurry components excluded from the settled layer, then dissolving said layer in water to form a solution and thereafter recovering purified alkali-metal azide from said solution by crystallization.