Iridium Sesquisulphate, Ir2(SO4)3.xH2O, is obtained by dissolving the hydrated sesquioxide in dilute sulphuric acid and allowing it to crystallise in the absence of air.
Unless special precautions are taken, the product has a violet colour due to the presence of iridium in a higher state of oxidation. By effecting the preparation of the salt in vacuo yellow crystals of sesquisulphate are obtained, which dissolve in water to a bright yellow solution. Exposure to air causes the solution to turn violet immediately, particularly if the solution is dilute. |