Two oxides of iridium are known, namely the sesquioxide, Ir203, and the dioxide, Ir02, corresponding to which there are two series of salts, the sesqui-salts and the iridic salts; a third series of salts is also known (the iridious salts) derived from an oxide IrO.
It is a bluish-black powder which at high temperatures decomposes into the metal, dioxide and oxygen.
Iridium dioxide, Ir0 2, may be obtained as small needles by heating the metal to bright redness in a current of oxygen (G.
Potassium iridium sesquichloride, K 3 IrC1 6.3H 2 O, is obtained by passing sulphur dioxide into a suspension of potassium chloriridate in water until all dissolves, and then adding potassium carbonate to the solution (C. Claus, Jour.
We can prepare, in the laboratory, a white powder that proves to be calcium carbonate, that is, it appears to be wholly composed of carbon dioxide and lime.
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