Platinum - Hackin

Pt. Atomic number 78. Platinum group element, or precious metal in group ¹⁰ of the periodic table ^, with electron configuration [Xe] ^4f145d96s1 . Atomic weight 195.084(9). There are five stable isotopes with mass numbers 190 (0.014(1)%), 192 (0.782(7)%), 194 (32.967(99)%), 195 (33.832(10)%), 196 (25.242(41)%), and 198 (7.163(55)%), and radioactive isotopes with mass numbers from 166 to 202. It was used in ornaments by ancient Egyptians and the Incas in South America (present-day Ecuador), but was only introduced to the West in the 16th century. The element's name comes from the fact that 17th century Spanish conquistadors called the silvery-white free platinum that is mined along with gold platina, meaning "little silver" (plata). In his book Shamitsu Kaishu, published in 1837, Udagawa Yoan referred to it as Platinum.
In nature, platinum exists in a free state (placer platinum) along with its homologous elements, but in South Africa platinum deposits are produced as sulfides, tellurides, and ferroplatinum alloys. Russia was once famous for its placer platinum in the Urals, but now, along with Canada, it produces a lot of arsenides. Ores include platinumite (PtS), arsenite (PtAs _{2 )} , and blagite (Pt,Pd,Ni)S. It is a mineral resource with a marked uneven distribution, with South Africa accounting for 90% of the world's total reserves and minable reserves, followed by Russia at 9%, and then Canada. The platinum content per ton of ore is said to be 3-8 g. Of the world's supply of 207 tonnes in 2007, South Africa supplied 162 tonnes. After crushing the ore, the platinum group metals are concentrated using flotation and gravity settling methods, and then smelted in an electric furnace, where the copper, nickel, etc. are magnetically separated. This is dissolved in aqua regia and separated from the insoluble silicates of osmium, iridium, rhodium, etc., and then treated with ammonium chloride to produce ammonium hexachloroplatinate(IV), (NH ₄ ) ₂ Pt ^Ⅳ Cl ₆ , from which palladium is separated. Alternatively, after concentrating the platinum group metals, it is treated with an aqueous HCl-Cl ₂ solution to produce [PtCl ₆ ] ^2-, which is then extracted with methyl isobutyl ketone, tri- n -octylamine, etc., and treated with ammonium chloride to precipitate (NH ₄ ) ₂ Pt ^Ⅳ Cl _6. This is then fired to produce platinum sponge. It is further refined by repeated re-dissolution and firing, or by electrolysis in a concentrated hydrochloric acid solution. A silvery-white metal. Cubic close-packed structure. Hardness 4.3. Highly ductile. Density 21.45 g cm ^-3 (20 °C). Melting point 1772 °C, boiling point 3830 °C. Oxidation numbers 2-6. Standard electrode potential Pt ²⁺ /Pt 1.188 V. First ionization energy 8.61 eV. Insoluble in any solvent except aqua regia, but reacts with chlorine and fluorine when red-hot. Attacked by molten NaOH. In reducing environments, it also reacts with P, Si, Pb, As, Sb, S, and Se. Like palladium, it adsorbs hydrogen. This tendency becomes more pronounced when it is red-hot, and platinum powder absorbs more than 100 times its volume of hydrogen. It also absorbs a considerable amount of oxygen and a small amount of helium. The absorbed hydrogen and oxygen are activated, so platinum powder, which has a large surface area, is often used as a catalyst (platinum catalyst). Its largest use as a catalyst is in automobile exhaust gas purification catalysts, with global demand in 2005 at 119 tons, accounting for 57% of total demand. Next is decorative items at 61.1 tons (29%). In Japan, 18.7 t (45%) was used in automobiles and 15.9 t (39%) was used in ornaments (total demand 40.9 t). Total imports were 61.3 t, of which 49 t (80%) came from South Africa. In addition to ornaments, due to its chemical stability, it is also used in crucibles (for high-grade glass such as LCDs), resistance thermometers, thermocouples, electrical contacts, etc. The prototype kilogram is an alloy of 90% platinum and 10% iridium. "Platinum and its water-soluble salts" are "dangerous and harmful substances whose names, etc. must be notified" under the Industrial Safety and Health Act, and "platinum and its compounds" are "harmful air pollutants" under the Air Pollution Control Act. [CAS 7440-06-4][See alternative terms] Platinum compounds

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

Pt．原子番号78の元素．電子配置[Xe]4f ¹⁴5d⁹6s¹の周期表10族貴金属または白金族元素．原子量195.084(9)．質量数190(0.014(1)％)，192(0.782(7)％)，194(32.967(99)％)，195(33.832(10)％)，196(25.242(41)％)，198(7.163(55)％)の5種の安定同位体と，質量数166～202の放射性同位体がある．古代エジプトや南米インカ(現在のエクアドル)で装飾品に使われていたが西欧に知られたのは16世紀．元素名は17世紀のスペイン征服者が金とともに産出する銀白色の遊離白金を“小さな銀”(plata)を意味するplatinaとよんだところから命名された．宇田川榕菴は天保8年(1837年)に出版した「舎密開宗」で，布刺知紐母(プラチニュム)としている．
天然には同族元素とともに遊離の状態(砂白金)で存在するが，南アフリカの白金鉱床は，硫化物，テルル化物，フェロ白金合金として産出する．ロシアは，かつてはウラルの砂白金が有名であったが，現在は，カナダとともにヒ化物を多く産出する．鉱石には硫白金鉱PtS，ヒ白金鉱PtAs₂，ブラグ鉱(Pt,Pd,Ni)Sなどがある．偏在のいちじるしい鉱物資源で，世界の全埋蔵量・可掘埋蔵量ともに南アフリカ90％，ロシア9％，ついでカナダである．鉱石1 t 当たりのPt含有率は3～8 g とされる．2007年度の世界の供給量207 t 中，南アフリカの供給量は162 t．鉱石を粉砕後，浮遊選鉱法，重力沈降法で白金族金属を濃縮して電気炉で製錬し，磁気的に銅，ニッケルなどを分離する．これを王水に溶かし，不溶のオスミウム，イリジウム，ロジウムなどのケイ酸塩と分離し，塩化アンモニウム処理によりヘキサクロロ白金(Ⅳ)酸アンモニウム(NH₄)₂Pt^Ⅳ Cl₆としてパラジウムと分離する．あるいは白金族金属濃縮後，HCl-Cl₂水溶液で処理して [PtCl₆]^2－ としてメチルイソブチルケトン，トリ-n-オクチルアミンなどで溶媒抽出し塩化アンモニウム処理で(NH₄)₂Pt^Ⅳ Cl₆を沈殿させる．これを焼いて白金海綿とする．再溶解，焼成の繰り返しや，濃塩酸溶液の電気分解でさらに精製する．銀白色の金属．立方最密構造．硬度4.3．展延性に富む．密度21.45 g cm^－3(20 ℃)．融点1772 ℃，沸点3830 ℃．酸化数2～6．標準電極電位 Pt^2＋/Pt 1.188 V．第一イオン化エネルギー8.61 eV．王水以外に溶けないが，赤熱状態では塩素，フッ素と反応する．溶融NaOHには侵される．還元的環境では，P，Si，Pb，As，Sb，S，Seなどとも反応する．パラジウムと同様に水素を吸着する．赤熱するとこの傾向はいちじるしくなり，微粉白金は容積の100倍以上の水素を吸収する．また，かなりの量の酸素，少量のヘリウムを吸収する．吸収された水素，酸素は活性化されるので，表面積の大きい微粉白金は触媒(白金触媒)として多用される．触媒としての最大の用途は自動車排気ガス浄化触媒で，2005年の世界の需要は119 t で全需要の57％ を占める．ついで装飾品用で61.1 t(29％)．わが国では，自動車用が18.7 t(45％)，装飾品用15.9 t(39％)であった(全需要量40.9 t)．全輸入量は61.3 t，うち南アフリカから49 t(80％)．装飾品の他，科学的に安定なことから，るつぼ(LCD用など高級ガラス用)，抵抗温度計，熱電対，電気接点などにも用いられる．キログラム原器は白金90％，イリジウム10％ の合金である．「白金及びその水溶性塩」は労働安全衛生法の「名称等を通知すべき危険物及び有害物」，「プラチナ及びその化合物」は大気汚染防止法の「有害大気汚染物質」である．[CAS 7440-06-4][別用語参照]白金化合物

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