Which metal attacks gold
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Area of Expertise - General Chemistry
The precious metals include the elements gold, silver, mercury, rhenium and the platinum metals ruthenium, rhodium, palladium, osmium, iridium and platinum.
Precious metals are not oxidized in the air under normal conditions; only in exceptional cases do they form thin oxide layers, and in the presence of sulfur-containing organic material occasionally also sulfide deposits (e.g. blackening of silver cutlery). Due to their resistance to atmospheric oxygen and water (corrosion resistance), the precious metals are often dignified in nature, i.e. they can be found in elemental form, mercury and silver also as sulfide or chloride. Other, occasionally also native metals, such as copper, arsenic, antimony, bismuth are not counted as precious metals but as semiprecious metals.
All noble metals have a low electron affinity and a more positive standard potential than hydrogen (see electrochemical series), i.e. they are not dissolved by water or non-oxidizing acids such as hydrochloric acid with the formation of hydrogen. Correspondingly, from a chemical point of view, copper would also belong to the noble metals, but is traditionally usually not included. Only with the use of oxidizing acids can precious metals be brought into solution, e.g. silver with nitric acid, gold and platinum with aqua regia. The metal is oxidized on the surface and the oxide is then dissolved from the acid.
The oxides of the noble metals often decompose into the metal and oxygen at higher temperatures.
Due to their small proportion in natural occurrences, very specific processing methods are usually required for the representation of the precious metals. Many precious metals are produced as by-products in the electrolytic refining of other metals, e.g. copper, in the so-called anode sludge. The costly and cost-intensive recovery of precious metals is increasingly being replaced by recycling such as photochemicals, catalysts, galvanic baths or electrical or electronic components.
The main industrial areas of application for precious metals include catalytic converters, especially in exhaust gas catalytic converters, and their use in microelectronics. Precious metals have played a special role since ancient times as valuable jewelry and foreign exchange material (coins, gold bars).
Learning units in which the term is dealt with
Platinum in medical technology45 min.
chemistryInorganic chemistryChemistry of the elements
Heraeus manufactures important components from metals and alloys for medical technology. Read about the role of platinum as a pacemaker application and aneurysm treatment.
Precious metal catalysts for homogeneous catalysis30 min.
chemistryInorganic chemistryHomogeneous catalysis
Read about a selection of outstanding examples of homogeneously catalyzed processes with precious metals that are used on a large scale in industry.
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