Editing Azide (section)

=== Purification of molten sodium ===
Sodium azide {{Chem2|NaN3}} is used to purify metallic sodium in laboratories handling molten sodium used as a coolant for [[fast-neutron reactor]]s.<ref name="Weber1951">{{Cite journal | last1=Weber | first1=C. E. | date=July 1948 – January 1951| title=Problems in the use of molten sodium as transfer fluid. OSTI declassified document | journal=Journal of Metallurgy and Ceramics | issue= 1 – 6 | page=291 | url=https://www.osti.gov/servlets/purl/4302453#page=202}}</ref>

As hydrazoic acid, the [[Protonation|protonated]] form of the azide anion, has a very low reduction potential (''E''°<sub>red</sub> = −3.09&nbsp;V), and is even a stronger [[Reducing agent|reductant]] than lithium (''E''°<sub>red</sub> = −3.04&nbsp;V), dry solid [[sodium azide]] can be added to molten metallic sodium (''E''°<sub>red</sub> = −2.71&nbsp;V) under strict anoxic conditions (''e.g.'', in a special anaerobic glovebox with very low residual {{O2}} {{Nowrap|(< 1 ppm vol.)}} to reduce {{Chem2|Na+}} impurities still present into the sodium bath. The reaction residue is only gaseous {{chem2|N2}}.

As ''E''°<sub>ox</sub> = −''E''°<sub>red</sub>, it gives the following series of oxidation reactions when the redox couples are presented as reductants: 
*{{Chem2|2 HN3 ⇌ 3 N2(g) + 2 H+ + 2 e-}} (''E''°<sub>ox</sub> = +3.09&nbsp;V)
*{{Chem2|Li ⇌ Li+ + e-}} (''E''°<sub>ox</sub> = +3.04&nbsp;V)
*{{Chem2|Na ⇌ Na+ + e-}} (''E''°<sub>ox</sub> = +2.71&nbsp;V)