Sodium azide is usually readily available; however, potassium azide is sometimes required due to its enhanced solubility, especially in aprotic solvents such as DMSO [3], or greater thermal stability (mp KN3 350°C, while sodium azide decomposes just above 275°C). Following is a very simple means for quickly preparing both azides by diazotization of hydrazine hydrate in alcohol, avoiding work with the highly toxic and explosive hydrazoic acid. The yield is about 86% for potassium azide and over 90% for sodium azide based on hydrazine (the former yield is smaller due to the ~10% water content in commercial potassium hydroxide, which retains some of the azide in solution). The potassium azide precipitates more slowly than sodium azide and in larger crystals and, hence, is easier to purify.