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The only lighter metals are the metals of groups 1 and 2, which apart from beryllium and magnesium are too reactive for structural use (and beryllium is very toxic). [29] Aluminium is not as strong or stiff as steel, but the low density makes up for this in the aerospace industry and for many other applications where light weight and relatively ...
Aluminium (or aluminum) metal is very rare in native form, and the process to refine it from ores is complex, so for most of human history it was unknown. However, the compound alum has been known since the 5th century BCE and was used extensively by the ancients for dyeing .
The use of polished stone axes marks a significant advance, because a much wider variety of rocks could serve as tools. A late Bronze Age sword- or dagger-blade. The innovation of smelting and casting metals in the Bronze Age started to change the way that cultures developed and interacted with each other.
An electrolytic cell is made of a steel shell with a series of insulating linings of refractory materials. The cell consists of a brick-lined outer steel shell as a container and support. Inside the shell, cathode blocks are cemented together by ramming paste. The top lining is in contact with the molten metal and acts as the cathode.
Many trivalent metals are capable of forming alums. The general form of an alum is XY (SO 4) 2 · n H 2 O, where X is an alkali metal or ammonium, Y is a trivalent metal, and n often is 12. The most important example is chrome alum, KCr(SO 4) 2 ·12 H 2 O, a dark violet crystalline double sulfate of chromium and potassium, was used in tanning.
Smelting involves more than just melting the metal out of its ore. Most ores are the chemical compound of the metal and other elements, such as oxygen (as an oxide), sulfur (as a sulfide), or carbon and oxygen together (as a carbonate). To extract the metal, workers must make these compounds undergo a chemical reaction.
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The metals of antiquity are the seven metals which humans had identified and found use for in prehistoric times in Africa, Europe and throughout Asia: [1] gold, silver, copper, tin, lead, iron, and mercury. Zinc, arsenic, and antimony were also known during antiquity, but they were not recognised as distinct metals until later.