PTL:Rhodium
From ChemEd Collaborative
Rhodium is a transition metal in Group VIIIB (Group 9) and the 5th period. It is one of the six platinum group elements: ruthenium, osmium, rhodium, iridium, palladium, and platinum.
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Discovered
The element was discovered in 1803 by W.H. Wollaston in the black residue left after dissolving crude platinum in aqua regia.
Name
He named the element after the Greek word for "rose" because of the color of aqueous solutions of rhodium(III).
Characteristics
Rhodium is exceedingly rare in the earth's crust (0.0001 ppm), about ten times less abundant than iridium. As a consequence, Rh is one of the most expensive elements, costing about $13,000 per 100 grams (in 1991).
Found
The most important sources of Rh are Ni-Cu-S ores in Canada and South Africa. It is only commercially feasible to extract the Rh from the nickel-bearing ore because so much of this ore is processed.
Because of its scarcity, only a 7-8 tons of Rh are produced each year. A great deal of the element is used in catalytic applications (e.,g., the control of automobile emissions).
Uses
However, its major use is in alloys with Pt and Pd, which gives a harder metal. These alloys are used in electrical furnace windings, [airplane sparkplugs and electrical contacts]. Plated Rh is exceptionally hard and highly reflective. These properties, combined with its resistance to corrosion, makes it ideal for optical instruments, as in [searchlight reflectors].
Emission Spectra
This is the emission spectra for Rhodium.
