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From 1889 to 1960, the meter was defined as the length of a platinum-iridium (90:10) alloy bar, known as the international prototype meter. The previous bar was made of platinum in 1799. Until May 2019, the kilogram was defined as the mass of the international prototype of the kilogram, a cylinder of the same platinum-iridium alloy made in 1879 ...
The most notable examples are the Platinum cat, [8] and Platinum Noble by the Isle of Man, Canadian Platinum Maple Leaf, [9] Chinese Platinum Panda and Australian Platinum Koala. [citation needed] The minting of a trillion-dollar platinum coin was proposed as a solution to the 2023 United States debt-ceiling crisis.
The seven metals known since Classical times in Europe were associated with the seven classical planets; this figured heavily in alchemical symbolism. The exact correlation varied over time, and in early centuries bronze or electrum were sometimes found instead of mercury, or copper for Mars instead of iron; however, gold, silver, and lead had ...
[9] [10] The design was based on the concept that the high melting point of platinum would allow it to operate at high temperatures and that the evacuated chamber would contain fewer gas molecules to react with the platinum, improving its longevity. Although it was an efficient design, the cost of the platinum made it impractical for commercial ...
The best known precious metals are the precious coinage metals, which are gold and silver. Although both have industrial uses, they are better known for their uses in art , jewelry , and coinage. Other precious metals include the platinum group metals: ruthenium , rhodium , palladium , osmium , iridium , and platinum , of which platinum is the ...
The oldest known iron objects used by humans are some beads of meteoric iron, made in Egypt in about 4000 BC. The discovery of smelting around 3000 BC led to the start of the Iron Age around 1200 BC [ 16 ] and the prominent use of iron for tools and weapons. [ 17 ]
Some explanations of Black Friday claim that the holiday references a 19th-century term for the day after Thanksgiving, during which plantation owners could buy slaves at discount prices.
Naturally occurring platinum and platinum-rich alloys were known by pre-Columbian Americans for many years. [5] However, even though the metal was used by pre-Columbian peoples, the first European reference to platinum appears in 1557 in the writings of the Italian humanist Julius Caesar Scaliger (1484–1558) as a description of a mysterious metal found in Central American mines between ...