The Iridium metal is not biologically useful and harmless because it does not react with biological tissues. Like most metals, the Iridium metal powder is dangerous. Such powders stimulate tissue and are easily burned in the air. Since the amount of iridium compound handled is generally low, little is known about its toxicity. However, soluble salts of iridium, such as various iridium halides, are toxic. Most of the iridium compounds are insoluble, so it is difficult to be absorbed by the body.
The chemical properties of Iridium are very stable. It is the most corrosion-resistant metal. Its chemical stability to acid is extremely high. It is insoluble in acid. Only sponge-like Iridium will dissolve slowly in hot aqua regia.
If Iridium metal is dense, even a boiling aqua regia, It can't be corroded ; however, in a closed reactor with high temperature and pressure, the Iridium is obviously corroded in the aqua regia above 250 °C; the mixed acid composed of 20 parts of concentrated hydrochloric acid and 1 part of concentrated nitric acid is at the above temperature Under pressure, the corrosiveness to Iridium is about 20 times that of aqua regia, so it is commonly used in chemical analysis to digest metal Iridium reagents.