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In chemistry, the noble metals are metals that are resistant to corrosion and oxidation in moist air (unlike most base metals). The short list of chemically noble metals (those elements upon which almost all chemists agree) comprises ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, and gold.〔A. Holleman, N. Wiberg, "Lehrbuch der Anorganischen Chemie", de Gruyter, 1985, 33. edition, p. 1486〕 More inclusive lists include one or more of mercury,〔(Die Adresse für Ausbildung, Studium und Beruf )〕〔"Dictionary of Mining, Mineral, and Related Terms", Compiled by the American Geological Institute, 2nd edition, 1997〕〔Scoullos, M.J., Vonkeman, G.H., Thornton, I., Makuch, Z., "Mercury - Cadmium - Lead: Handbook for Sustainable Heavy Metals Policy and Regulation",Series: Environment & Policy, Vol. 31, Springer-Verlag, 2002〕 rhenium〔The New Encyclopædia Britannica, 15th edition, Vol. VII, 1976〕 or copper as noble metals. On the other hand, titanium, niobium, and tantalum are not included as noble metals although they are very resistant to corrosion. While the noble metals tend to be valuable – due to both their rarity in the Earth's crust and their usefulness in areas like metallurgy, high technology, and ornamentation (jewelry, art, sacred objects, etc.) – the terms "noble metal" and "precious metal" are not synonymous. The term ''noble metal'' can be traced back to at least the late 14th century〔http://dictionary.reference.com/browse/noble+metal〕 and has slightly different meanings in different fields of study and application. Only in atomic physics is there a strict definition. For this reason there are many quite different lists of "noble metals". In addition to this term's function as a compound noun, there are circumstances where "noble" is used as an adjective for the noun "metal". A "galvanic series" is a hierarchy of metals (or other electrically conductive materials, including composites and semimetals) that runs from ''noble'' to ''active'', and allows one to predict how materials will interact in the environment used to generate the series. In this sense of the word, graphite is more noble than silver and the relative nobility of many materials is highly dependent upon context, as for aluminium and stainless steel in conditions of varying pH.〔Everett Collier, "The Boatowner’s Guide to Corrosion", International Marine Publishing, 2001, p. 21〕 == Properties == Palladium, platinum, gold and mercury can be dissolved in aqua regia, a highly concentrated mixture of hydrochloric acid and nitric acid, but iridium and silver cannot. Silver is, however, soluble in pure nitric acid. Ruthenium can be dissolved in aqua regia only when in the presence of oxygen, while rhodium must be in a fine pulverized form. Niobium and tantalum are resistant to all acids, including aqua regia. 〔A. Holleman, N. Wiberg, "Inorganic Chemistry", Academic Press, 2001〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「noble metal」の詳細全文を読む スポンサード リンク
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