Rhodium

Notable characteristics

Rhodium is a hard silvery white and durable metal that has a high sulfuric acid.

Applications

The primary use of this element is as an alloying agent for hardening electrodes for aircraft spark plugs, and laboratory crucibles. Other uses include:

• It is used as an electrical contact material due to its low electrical resistance, low and stable corrosion resistance.
• Plated rhodium, made by electroplating or evaporation, is extremely hard and is used for optical instruments.
• This metal finds use in jewelry and for decorations. It is electroplated on white gold and platinum to give it a reflective white surface. This is known as rhodium flashing in the jewelry business. It also may be used in coating sterling silver.
• It is also a highly useful Monsanto process). It is used to catalyse addition of hydrosilanes to a double bond, a process important in manufacture of certain silicone rubbers.
• The complex of a rhodium ion with menthol.
• It is also used as a filter in mammography systems because of the characteristic x-rays it produces.

History

Rhodium (Greek rhodon meaning "rose") was platinum ore that he presumably obtained from South America.

His procedure involved dissolving the ore in hydrogen gas.

Occurrence

Normal mining

The industrial extraction of rhodium is complex as the metal occurs in ores mixed with other metals such as minerals. It is generally difficult to determine if a rock sample contains platinum group elements. As of October 2007, rhodium cost approximately eight times more than gold, 450 times more than silver, and 27,250 times more than copper by weight. Rhodium's typical historical price is about $1,000/troy oz,^[5] but in recent years it has increased to about $6,150/troy oz.^[6]

As a fission product

It is also possible to extract rhodium from fission products of ²³⁵U contain 13.3 grams of ¹⁰³Rh. So as a typical used fuel is 3% fission products by weight it will contain about 400 grams of rhodium per ton of used fuel. The longest lived radioisotope of rhodium is ^102mRh which has a half life of 2.9 years, while the ground state (¹⁰²Rh)has a half life of 207 days.

Each kilo of fission rhodium will contain 6.62 ng of ¹⁰²Rh and 3.68 ng of ^102mRh. As ¹⁰²Rh decays by gamma ray photons with about 1 MeV are generated). If the fission occurs in an instant then 13.3 grams of rhodium will contain 67.1 MBq (1.81 mCi) of ¹⁰²Rh and 10.8 MBq (291 μCi) of ^102mRh. As it is normal to allow used nuclear fuel to stand for about five years before reprocessing, much of this activity will decay away leaving 4.7 MBq of ¹⁰²Rh and 5.0 MBq of ^102mRh. If the rhodium metal was then left for 20 years after fission, then the 13.3 grams of rhodium metal would contain 1.3 kBq of ¹⁰²Rh and 500 kBq of ^102mRh. At first glance the rhodium might be adding to the resource value of reprocessed fission waste, but the cost of the separation of the rhodium from the other metals needs to be considered.

 

Isotopes

Main article: isotopes of rhodium

Naturally occurring rhodium is composed of only one isotopes of rhodium.

The primary palladium.

Precautions

Rhodium metal is, as a noble metal, inert.

However, when rhodium is chemically bound, it is reactive. Rhodium compounds are not often encountered by most people and should be considered to be highly toxic and carcinogenic^{[citation needed]}. Lethal intake (LD50) for rats is 12.6 mg/kg of rhodium chloride (RhCl₃)^{[citation needed]}. Rhodium compounds can stain human skin very strongly. The element plays no biological role in humans. However, if used plainly, without compounds, the metal is harmless.

Symbolic uses

Rhodium has been used for honours, or to symbolize wealth, when more commonly used metals such as silver, gold, or platinum are deemed insufficient. In 1979 the Guinness Book of World Records gave Paul McCartney a rhodium-plated disc for being history's all-time best-selling songwriter and recording artist. Guinness has also noted items such as the world's "Most Expensive Pen" or "Most Expensive Board Game" as containing rhodium.

See also

• Rhodium compounds

References

1. ^ Rhodium: rhodium(I) fluoride compound data. OpenMOPAC.net. Retrieved on 2007-12-10.
2. ^ http://www.taxfreegold.co.uk/preciousmetalpricesindx.html
3. ^ Emsley, John (2001). Nature's Building Blocks, (Hardcover, First Edition), Oxford University Press, page 363. ISBN 0198503407. 
4. ^ WebElements - The History of Rhodium
5. ^ http://periodic.lanl.gov/elements/45.html
6. ^ KITCO Rhodium Price Charts