For the first time in 1803 Rhodium was discovered. It was dissolved in aqua regia, and formed a black lagging. The chemical element Rhodium is a transition metal which is silver-white and hard. It is even tougher than platinum or gold, very elastic and tough. At best it can be processed by hammers. The element is preferably used in catalytic converters and used with nitrogen oxides. The production is very expensive since they can be difficult to separate. By auqa regia remains unsolved the element rhodium back. The residue is melted with sodium bisulfate, so that rhodium is separated from other elements.
At times, with a price of rhodium was about ten times more expensive than gold 10000 USD / Unze, now is the price back down to 1100 USD / Unze