|Name: palladium||Group number: 10|
|Symbol: Pd||Group name: Precious metal or Platinum group metal|
|Atomic number: 46||Period number: 5|
|Atomic weight: 106.42 (1) g||Block: d-block|
|CAS Registry ID: 7440-05-3||Voice: |
|Standard state: solid at 298 K||Colour: silvery white metallic|
|Classification: Metallic||Availability: |
This sample is from The Elements Collection, an attractive and safely packaged collection of the 92 naturally occurring elements that is available for sale.
Palladium is a steel-white metal, does not tarnish in air, and is the least dense and lowest melting of the platinum group metals. When annealed, it is soft and ductile. Cold working increases its strength and hardness. It is used in some watch springs.
At room temperatures the metal has the unusual property of absorbing up to 900 times its own volume of hydrogen. Hydrogen readily diffuses through heated palladium and this provides a means of purifying the gas.
IsolationHere is a brief summary of the isolation of palladium.
It would not normally be necessary to make a sample of palladium in the laboratory as the metal is available commercially. The industrial extraction of palladium is complex as the metal occurs in ores mixed with other metals such as platinum. Sometimes extraction of the precious metals such as platinum and palladium is the main focus of a partiular industrial operation while in other cases it is a byproduct. The extraction is complex and only worthwhile since palladium is the basis of important catalysts in industry.
Preliminary treatment of the ore or base metal byproduct with aqua regia (a mixture of hydrochloric acid, HCl, and nitric acid, HNO3) gives a solution containing complexes of gold and platinum as well as H2PdCl4. The gold is removed from this solution as a precipitate by treatment with iron chloride (FeCl2). The platinum is precipitated out as (NH4)2PtCl6 on treatment with NH4Cl, leaving H2PdCl4 in solution. The palladium is precipitated out by treatment with ammonium hydroxide, NH4OH, and HCl as the complex PdCl2(NH3)2. This yields palladium metal by burning.