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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. In general, alums are formed more easily when the alkali metal atom is larger.
Aluminium (or aluminum in North American English) is a chemical element; it has symbol Al and atomic number 13. Aluminium has a density lower than that of other common metals, about one-third that of steel. It has a great affinity towards oxygen, forming a protective layer of oxide on the surface when exposed to air.
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 .
How the Metal Was Discovered. Scientists and technologies associated with the first attempts to produce pure aluminium; the beginning of the industrial production of the metal and birth of aluminium manufacturing in different countries of the world; use of cryolite; deployment of aluminium in the 19th century; first machine-made aluminium products.
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The Spanish language is one of many major languages with limited use in science and technology. The main cause of this is the proliferation of English in scientific writing, which has been ongoing since English displaced French and German as the languages of science in the first half of the 20th century. [9]
Early coinage made from metal came into use during the Axial Age in the Greek world, in northern India, and in China, as coins became a widespread embodiment of money. [2] Bronze, gold, silver and electrum (a naturally occurring pale yellow mixture of gold and silver that was further alloyed with silver and copper) were used.
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