イリジウム 化学特性,用途語,生産方法
外観
灰色～銀灰色, 粉末
性質
銀白色の金属。硬くてもろく、加工性に乏しい。イリジウムは，硬いことと融点が高いことでは白金族中オスミウムに次ぐ。またその比重は実存する物質中もっとも大きい。質量数185から198にわたり多くの放射性同位体が存在する。典型的な貴金属で、塊状のものはすべての酸に不溶で、王水にさえおかされない。粉状にして初めて王水に溶ける。空気中で800℃から酸化し始めるが、高温では酸化物が分解するので、1140℃以上では酸化されない。水酸化アルカリとは融解状態でも反応しないが、融解した二硫酸カリウムや硝酸カリウムには溶ける。赤熱状態でフッ素、塩素と容易に反応する。化合物中では1、3、4その他多くの酸化状態をとる。
溶解性
通常の酸、アルカリ、水にほとんど溶けない。王水にも溶けにくい。
解説
Ir．原子番号77の元素．電子配置[Xe]4f 145d76s2の周期表9族(白金族)貴金属元素．元素名は，イリジウム化合物の多彩な色彩から虹の女神を意味するギリシア語Ιριζ"(Iris)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，意利胄母(イリヂュウム)としている．原子量192.217(3)．質量数191(37.3(2)％)，193(62.7(2)％)の安定同位体のほか，質量数164～198の放射性同位体が知られている．1804年，S. Tennantが発見．白金鉱中に単体あるいは合金として存在する．地殻中の存在度0.0001 ppm．ニッケルや銅の製造の際に副産物として得られる．銀白色のもろい金属．融点2410 ℃，沸点約4130 ℃．密度22.67 g cm－3(20 ℃)．硬さ6.5．標準電極電位 Ir3＋/Ir 1.156 V．第一イオン化エネルギー9.02 eV．酸化数1～4．ロジウム同様耐酸性が大きく，粉末にしないと王水にも溶けない．イリジウム海綿は水素を吸収する．高温では酸化物は揮発性を示す．Irの多い地層は宇宙物質起源のものを含むと考えられている．白金族元素との合金として利用される．オスミウムとの合金イリドスミンは万年筆のペン先に利用されている．石油改質触媒に白金とともに用いられる．半導体結晶生成用のるつぼ材，自動車用点火プラグ材料に用いられる．192Ir は非破壊検査用γ線源．白金との合金はかつてメートル原器に用いられた．森北出版「化学辞典（第2版）
用途
合金材料、水素貯蔵合金研究、触媒研究用。
用途
純イリジウムは分析用、高温反応用るつぼ、高溶融点ガラスの押し出し用ダイスなど特別の用途がある。主要な需要は白金との合金で、装身具、外科手術用の針、旋回軸、電気接点などに用いられる。メートル原器も10％イリジウム合金である。オスミウムとの合金は万年筆のペン先として普及している。
用途
イリジウムやイリジウムを用いた合金は、その硬度や融点の高さから耐熱性や耐摩耗性が求められる用途で使用されることが多い。
LEDなどの原料として使用する人工サファイアの単結晶を製造するための工業用のるつぼは非常に高い耐熱性が求められるため、イリジウムはるつぼの材料[7]として欠かせない存在となっており、イリジウムの用途として最も一般的である。
耐食性?耐摩耗性に優れていることから高級万年筆のペン先の材料としてオスミウムなどと共に用いられることもある。
白金とイリジウムの合金(Pt-10Ir)は、キログラム原器やメートル原器の材料として使われていることでも知られている。
人工的に作った放射性同位体のイリジウム192(192Ir)は、非破壊検査の際の線源として利用されている。
イリジウムは、白金の割り金として使用されることが多く、指輪やネックレスなどの多くの宝飾品に用いられている。
また、近年ではイリジウムそのものが結婚指輪などの材料として用いられることもある。
化学的特性
Black Powder
物理的性質
Iridium is a hard, brittle, white, metallic substance that is almost impossible to machine.It is neither ductile nor malleable. Iridium will only oxidize at high temperatures and is themost corrosive-resistant metal known. This is why it was used to make the standard meter barthat is an alloy of 90% platinum and 10% iridium.
At about the time of the French Revolution, it was decided to determine the length ofthe meter bar by first calculating the distance from the North Pole to the equator runningthrough Paris. This distance was then divided into equal lengths of 1/10,000,000. A singleunit of this distance was then called a “meter” (“measure” in Greek). This platinum-iridiummeter bar, currently preserved in France, was for many years the standard unit of lengthin the metric system that is based on the decimal system. However, this metal bar is nolonger used as the standard meter. Instead, the meter is now defined by scientists in termsof the length of the path traveled by light in a vacuum at the time of 1/299,792,458 of asecond.
Iridium is highly resistant to attack by other chemicals and is one of the most dense elementsfound on Earth. Its melting point is 2,410°C, its boiling point is 4,130°C, and itsdensity is 22.560 g/cm
3.
同位体
There are 55 isotopes of iridium, two of which are stable and account for theelement’s total existence on Earth. Those two are Ir-191, which makes up 37.3% of theamount in the Earth’s crust, and Ir-193, which constitutes 62.7% of iridium’s existenceon Earth. All the other 53 isotopes of iridium are radioactive with half-lives ranging froma few microseconds to a few hours or days and up to a few hundred years. Theseunstable isotopes are all artificially produced.
名前の由来
The name iridium comes from the Latin word iris, meaning “rainbow,”
because of the element’s highly colored salts.
天然物の起源
Iridium is the 83rd most abundant element and is found mixed with platinum, osmium,and nickel ores. The minerals containing iridium are found in Russia, South Africa, Canada,and Alaska.
Iridium metal is separated from its other metal ores when the combined minerals aredissolved with a strong acid know as aqua regia, which is a mixture of 25% nitric acid and75% hydrochloric acid. Aqua regia is the only acid that will dissolve platinum and gold.Once the platinum and other metals are dissolved, the iridium, which is insoluble in thisstrong acid, becomes the residue. The refined iridium ends up in the form of either powderor crystals.
An interesting story as to how most of the iridium appeared on Earth was explainedrecently by scientists who discovered a thin layer of iridium in the sediments that were laiddown in the Earth’s crust at the end of the Cretaceous period. This was a period about 65 millionyears ago when meteors and asteroids crashed into the Earth. These extraterrestrial bodiescontained a high percentage of iridium. Dust from the impact spread around the Earth andblocked the sun for months, resulting in the extinction of many plants and animals, includingthe dinosaurs. This extensive dust cloud also deposited a thin coat of the element iridium thatwas contained in the fiery bolides.
特性
Iridium is one of the so-called platinum group of 6 transition elements (Ru, Rh, and Pd ofperiod 5 and Os, Ir, and Pt of period 6). It is resistant to strong acids, including aqua regia.It is the only metal that can be used in equipment that must withstand temperatures up to2,300°C or 4,170°F. Iridium can be poured into casts after it becomes molten. As it cools, itbecomes crystalline and, while in this state, can be pulled into wires and formed into sheets.Unlike steel, which becomes more malleable (less brittle) after annealing (a process of heatingfollowed by slowly cooling), iridium is just the opposite—it becomes more brittle and impossibleto work into shapes after cooling.
使用
Iridium’s most common use is as an alloy metal that, when added to platinum, makes itharder and more durable. It is also mixed with other metals to make electrical contacts, thermocouples(two dissimilar metals joined to form a special type of thermometer), and instrumentsthat will withstand high temperatures without breaking down. It is also used to makespecial laboratory vessels because iridium will not react with most chemical substances. Analloy of iridium and platinum is used as the standard kilogram weight because it is noncorrosiveand will not oxidize and, thus, change its weight over long periods of time.
The radioisotope, iridium-192, is used to treat cancer and to take X-ray pictures of metalcastings to detect flaws. Iridium is also used as a catalyst for several chemical reactions.
定義
iridium: Symbol Ir. A silvery metallictransition element; a.n. 77; r.a.m. 192.20;r.d. 22.42; m.p. 2410°C; b.p. 4130°C.It occurs with platinum and ismainly used in alloys with platinumand osmium. The element forms arange of iridium(III) and iridium(IV)complexes. It was discovered in 1804by Smithson Tennant (1761–1815).
危険性
The elemental metal form of iridium is almost completely inert and does not oxidizeat room temperatures. But, as with several of the other metals in the platinum group,several of iridium’s compounds are toxic. The dust and powder should not be inhaled oringested.
工業用途
Iridium (symbol Ir) is a grayish-white metal ofextreme hardness. It is insoluble in all acids andin aqua regia. The melting point is 2447°C, andthe specific gravity is 22.50. It occurs naturallywith the metal osmium as an alloy, known asosmiridium, 30 to 60% osmium, used chieflyfor making fountain-pen points and instrumentpivots.
Iridium is employed as a hardener for platinum,the jewelry alloys usually containing10%. With 35% iridium the tensile strength ofplatinum is increased to 965 MPa. Iridium wireis used in spark plugs because it resists attackof leaded aviation fuels.
Because of its scarcity and high cost, applications of iridium are severely limited. Although iridium metal and many of its complex compounds are good catalysts, no large-scale commercial application for these has been developed. In general, other platinum metals have superior catalytic properties. Platinum-iridium alloys are used for electrodes in spark plugs that are unusually resistant to fouling by antiknock lead additives. Iridium rhodium thermocouples are used for high-temperature applications, where they have unique stability.
純化方法
Iridium is a silver white hard solid which oxidises on the surface in air. Scrape the outer tarnished layer until silver clear and store it under paraffin. It is stable to acids but dissolves in aqua regia. [Gilchrist Chem Rev 32 277 1943.]
Structure and conformation
The space lattice of Ir belongs to the cubic system, and its face-centered cubic lattice has a lattice
constant of a=0.38312 nm and Ir–Ir=0.2709 nm (18℃).
イリジウム 上流と下流の製品情報
原材料
準備製品