Tetraiodine nonoxide is an iodine oxide with the chemical formula I4O9.
Preparation Tetraiodine nonoxide can be produced by reacting ozone and iodine in carbon tetrachloride at −78 °C:
It can also be produced by heating iodic acid and phosphoric acid together:
Properties Tetraiodine nonoxide is a light yellow solid that can easily hydrolyze. It decomposes above 75 °C:
Like diiodine tetroxide, tetraiodine nonoxide contains both I(III) and I(V), and disproportionates to iodate and iodide under alkaline conditions:
It reacts with water to form iodic acid and iodine:
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