Platinum Metals Review - Volume 18, Issue 3, 1974

Iridium is used extensively as a material for crucibles containing oxide melts during single crystal growth because of good chemical compatibility with them in slightly oxidising atmospheres. With care, iridium crucibles can be used in this way for long periods.

Rhodium-platinum gauzes used as catalysts in nitric acid plants operating at various pressures have been examined by microscopy and by X-ray diffraction. Some gauzes possess low conversion efficiency and these are usually covered with deposits that can frequently be traced to sources of contamination. Gauzes operated at pressures of four or more atmospheres also possess coatings of rhodium oxide that are difficult to remove by fusion or pickling. The suggested cause of formation of this oxide shows that it cannot be avoided but that methods exist for cleaning gauzes from higher pressure plants.