Sodium azide is a highly toxic chemical, which exists as an odorless white solid. Its solution in water is slowly hydrolyzed into a very toxic gas, hydrogen azide (HN3), which also forms when NaN3 reacts with a strong acid. It may react with heavy metal ions such as copper, silver or lead to form metal azides which are very unstable, easily synthesized, and highly explosive. When pure, it is a white crystalline solid, odorless, and easily soluble in water. It is slightly soluble in ethanol and starts to decompose vigorously to sodium metal and nitrogen gas at approximately 300 °C. It is very toxic to the aquatic environment, and so the disposal of this substance should be carefully regulated. It should be destroyed by oxidation or reduction before being released to the environment.