Iodine azide reaction

The iodine-azide reaction is used to detect sulfide by reacting with iodine / azide in qualitative inorganic analysis. Pure solutions of sodium azide (NaN ₃ ) and iodine (I ₂ ) are stable together for a long time. However, they are catalytically decomposed by the action of S ²⁻ (also sparingly soluble heavy metal sulfides). Thiocyanates (SCN ^- ) react analogously.

${\displaystyle \mathrm {S^{2-}+I_{2}\longrightarrow S+2\ I^{-}} }$

Sulphide anions and iodine react to form sulfur and iodide. (Discoloration)

${\displaystyle \mathrm {S+2\ N_{3}^{-}\longrightarrow S^{2-}+3\ N_{2}\uparrow } }$

Sulfur and azide ions react to form sulfide and molecular nitrogen. (Gas development)

Larger amounts of I ^- disrupt the reaction. In this case, adding a few drops of Hg (NO ₃ ) ₂ solution causes the formation of HgI ₄ ²⁻ . The latter has no effect on the described catalytic decomposition of iodine / azide.

literature

• Gerdes: Qualitative Inorganic Analysis, Springerverlag, 2nd edition, ISBN 978-3540670186

Web links

Wikibooks: Practical Course Inorganic Chemistry / Sulphide # Iodine-Azide Reaction  - Learning and teaching materials