Palladium

1.02%

{ syn. }

11.14%

22.33 %

27.33 %

{ syn. }

26.46 %

{ syn. }

11.72 %

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Palladium is a chemical element with the chemical symbol Pd and atomic number 46 The rare silver-white transition metal is one of the platinum metals in the periodic table it is in the fifth period and the group 10 (formerly part of the 8th transition group) or nickel group. It is similar in chemical behavior very platinum.

History

Palladium was discovered in 1803 by William Hyde Wollaston. He named it in 1804 after two years earlier discovered asteroid Pallas. Wollaston found element 46 in the south american platinum ore due to low yields of platinum from dissolved in aqua regia samples.

2010, came to the attention of world public opinion: Three researchers were awarded the Nobel Prize in Chemistry for a method that enables as a catalyst by means of palladium -effective ways to connect carbon atoms to complex molecules.

Occurrence

Metallic palladium and palladium-containing alloys are mainly found in river sediments as a geological soaps in the Ural Mountains, Australia, Ethiopia, and in North and South America. However, they are largely exploited for decades.

Today it is mostly derived from nickel and copper ores. In 2011 came about 41 percent ( 85,000 kg ) of Russian extraction, followed by South Africa with about 37.5 percent ( 78,000 kg ). By far Canada followed with nearly 9 percent ( 18,000 kg ) and the United States with 6 percent (12,500 kg). In the " platinum group metal " (platinum, palladium, iridium, osmium, rhodium and ruthenium) with South Africa has 63 million kilograms of world reserves of about 66 million kg more than 95 percent of global reserves.

With the Altwagenentsorgung the proportion of recycled palladium from the catalytic converters will increase. About the possibility of recovery of palladium from spent fuel, see Synthesis precious metal. By di-n- hexylsulfid palladium can be separated selectively from other metals from hydrochloric acid solutions.

→ platinum metals / Tables and Charts

Properties

Physical Properties

Palladium is a metal and the second element of the group nickel. It has the elements of this group the lowest melting point and is also the most reactive. At room temperature, it does not react with oxygen. It retains its metallic luster in the air and does not tarnish. When heated to about 400 ° C due to the formation of an oxide layer of palladium (II ) oxide it runs on steel blue. At about 800 ° C, the oxide decomposes again, the surface is bare again. In the annealed condition, it is soft and ductile when cold deformation, the strength and hardness increases but quickly ( strain hardening ). It's a lot harder than platinum. At temperatures above 500 ° C. Palladium is sensitive to sulfur and sulfur compounds (e.g., gypsum). Is formed of palladium ( II ) sulphide, which leads to embrittlement of palladium and palladium alloys.

Chemical Properties

Palladium is a precious metal, although it is significantly more reactive than the related Element Platinum: It dissolves in nitric acid with palladium (II ) nitrate Pd ( NO3) 2 is formed. It also dissolves in aqua regia and in hot concentrated sulfuric acid. In hydrochloric acid it dissolves slowly on contact with air to form PdCl42 -. The noble character of palladium is that of the adjacent silver comparable: in hydrochloric acid it behaves due to the formation of slightly soluble palladium chloride compounds ignoble. In a humid atmosphere in the presence of sulfur, the surface of palladium is clouded.

Palladium has the highest absorbency of all elements hydrogen. This fundamental discovery goes back to Thomas Graham in 1869. At room temperature, it may be the 900 -fold, palladium black 1200 -fold and bind the colloidal palladium solutions, 3000 times its own volume. One can describe the uptake of hydrogen as a loosening of hydrogen in the metal lattice and the formation of a palladium hydride with the approximate composition Pd2H. At 30 ° C and atmospheric pressure corresponds to the maximum hydrogen - palladium ratio of the formula PdH0, 608

Usually it takes in the oxidation states 2 and 4. For compounds of the apparent oxidation state 3 is Pd (II) / Pd (IV) mixing compounds. Recent studies also hexavalent palladium could be shown. However, there are 0 [ Pd ( PR3 ) 4], 1 or 5 possible oxidation states.

Safety

In compact form is not combustible, but highly flammable as powder or dust.

Use

Finely divided palladium is an excellent catalyst for the acceleration of chemical reactions, especially hydrogenation reactions and dehydrogenation reactions (addition and removal of hydrogen), and the cracking of hydrocarbons.

Other applications:

  • Catalytic converters for gasoline engines. (Palladium displaces the more expensive platinum. )
  • Jewelry (especially in East Asia )
  • Damen-/Herrenuhren
  • White Gold ( palladium " discolored " Gold)
  • Platinum crucible (80 % Pt, 20 % Pd)
  • Feinstfolien. Similar to the gold leaf, palladium can be rolled to 0.01 micron thin films.
  • Palladium sheet by hot hydrogen diffuses virtually without resistance, whereby it can be used for the purification of hydrogen. In hot palladium hydrogen has a high diffusivity.
  • Contact materials for relay in communications systems
  • Dentures
  • Medical instruments
  • Electrode materials for fuel cells and spark plugs ( Aviation)
  • Pd / Ni alloys as a replacement for gold in the electronics industry ( for example in the electroplating of contact )
  • Nanotechnology ( acts as a catalyst to produce molecular weight compounds, for example )
  • Bullion coins, such as Palladium Maple Leaf
  • Springs for fountain pens
  • P-contact for galliumnitridbasierte semiconductor devices
  • Alloying of the material titanium, as Grade 7 - and 11- grade alloy
  • In GASFET sensors as gate
  • In printed circuit board coating: the plastic, sometimes even holes ( seeding ) is coated with palladium to it, apply a copper or brass layer.
  • 2011 was an extremely durable, amorphous material - so-called metallic glass - with the main component ( about 40 % ) of palladium produced, does not have the typical for this class of material brittleness.

Palladium Price

The name of palladium, which is traded on the stock exchange, XPD is. The International Securities Identification Number ISIN is XC0009665529.

Compounds

Most of the palladium compounds have a quadratic structure. A group of researchers at the University of Oldenburg has been able to connect Palladiumdisulfat, Pd ( S2O7 ) to synthesize with an octahedral structure. The special feature of this compound is the ferromagnetic property at low temperatures, which has not yet been observed in palladium compounds.

→ Category: palladium compound

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