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Rhodium


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Atomic Number:45Atomic Symbol:Rh
Atomic Weight:102.9055Electron Configuration:2-8-18-16-1
Shells:2,8,18,16,1Filling Orbital:4d8
Melting Point:1966oCBoiling Point:3727oC
Description:Hard silvery white metal
Uses:Used as a coating to prevent wear on high quality science equipment and with platinum to make thermocouples. Also used for headlight reflectors.

History

(Gr. rhodon, rose). William Wollaston of England discovered rhodium in 1803-4 in crude platinum ore he presumably obtained from South America.

Sources

Rhodium occurs native with other platinum metals in river sands of the Urals and in North and South America. It is also found with other platinum metals in the copper-nickel sulfide area of the Sudbury, Ontario region. Although the quantity occurring here is very small, the large tonnages of nickel processed make the recovery commercially feasible. The annual world production of rhodium is only 7 or 8 tons.

Properties

  • The metal is silvery white and at red heat slowly changes in air to the resquioxide.
  • At higher temperatures it converts back to the element.
  • Rhodium has a higher melting point and lower density than platinum.

Uses

  • Its primary use is as an alloying agent to harden platinum and palladium.
  • Such alloys are used for furnace windings, thermocouple elements, bushings for glass fiber production, electrodes for aircraft spark plugs, and laboratory crucibles.
  • It is useful as an electrical contact material as it has a low electrical resistance, a low and stable contact resistance, and is highly resistant to corrosion.
  • Plated rhodium, produced by electroplating or evaporation, is exceptionally hard and is used for optical instruments.
  • It has a high reflectance and is hard and durable.
  • Rhodium is also used for jewelry, for decoration, and as a catalyst.

Handling

Exposure to rhodium (metal fume and dust, as Rh) should not exceed 1 mg/m^3 (8-hour time-weighted average, 40-hour week).

Costs

Rhodium costs about $1,000/troy oz.

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