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Blue Bronze
In chemistry, molybdenum bronze is a generic name for certain mixed oxides of molybdenum with the generic formula where A may be hydrogen, an alkali metal cation (such as lithium, Li+, sodium, Na+, potassium, K+), and thallium, Tl+. These compounds form deeply coloured plate-like crystals with a metallic sheen, hence their name. These bronzes derive their metallic character from partially occupied 4d bands. The oxidation states in K0.28MoO3 are K+1, O2−, and Mo+5.72. MoO3 is an insulator, with an unfilled 4d band. These compounds have been much studied since the 1980s due to their markedly anisotropic electrical properties, reflecting their layered structure. The electrical resistivity can vary considerably depending on the direction, in some cases by 200:1 or more. They are generally non-stoichiometric compounds. Some are metals and some are semiconductors. Preparation The first report of a "molybdenum bronze" was by Alfred Stavenhagen and E. Engels in 1895. They repor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hepatizon
''Hepatizon'' (Greek etymology: , English language, English translation: "liver"), also known as black Corinthian bronze, was a highly valuable metal alloy in classical antiquity. It is thought to be an alloy of copper with the addition of a small proportion of gold and silver (perhaps as little as 8% of each), mixed and treated to produce a material with a dark purplish patina, similar to the colour of liver. It is referred to in various ancient texts, but few known examples of hepatizon exist today. Of the known types of bronze or brass in classical antiquity (known in Latin as ''aes'' and in Greek as χαλκός), hepatizon was the second most valuable. Pliny the Elder mentions it in his ''Naturalis Historia, Natural History'', stating that it is less valuable than Corinthian bronze, which contained a greater proportion of gold or silver and as a result resembled the precious metals, but was esteemed before bronze from Delos and Aegina. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
