Na3[IrCl6] + 4HNO3 + H2O → IrO2 + NO2 + 3NaNO3 + 6HCl
Sodium hexachloridoiridate(III) react with nitric acid and water to produce iridium(IV) oxide, nitrogen dioxide, sodium nitrate and hydrogen chloride. Nitric acid - concentrated solution. The reaction takes place in a boiling solution.