The gold and the silver call noble metals no so much because they are scarce and beautiful, but because no oxidan, as the majority of the others metals, when being exposed to the air.
Sometimes the objects of silver deslustran; the cause of this is that they are attacked by the acid sulfhídrico that there is occasionally in the air, but no because oxiden frankly.
Another reason of his nobility is that it results very difficult to dissolve them; the only that dissolves to the gold is a mix of two very strong acids: the nitric acid and the acid clorhídrico. Each one of the two work very quickly on a lot of metals, but any of them attacks separately the gold, which only can be it by a mix of both; this mix has come calling during long regal water, because it could dissolve the real and noble metal, that is to say, the gold.
The gold and the silver are metals very beautiful to his way, but his utility is small compared with the enormous utility of the iron.
We have seen that the gold no oxida usually, neither exist special methods that attain it; instead the silver can be oxidada if it heats it to him to tall temperatures and exposes it to him to the air or to the oxygen.
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