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性質
ルビジウムは、銀白色の柔らかくて、非常に軽い金属です。炎色反応で、カリウムと似た暗赤色を示します。融点が低く、39°Cです。沸点は688 °Cで、気体は青色です。
特性は他のアルカリ金属に似ています。非放射性のアルカリ金属元素の中で電気陰性度が2番目に小さく、イオン化エネルギーも406 kJ/molととても低いです。
化合物中の原子価は+1です。ルビジウムイオンは、カリウムイオンと同様に、植物や動物の細胞に取り込まれます。
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反応
ルビジウムの反応性は、他のアルカリ金属と似ています。ただし、カリウムやナトリウムよりも反応性があります。空気中でルビジウムは自然発火し、すぐに酸化して過酸化物のRb2O2や超酸化物のRbO2を生成可能です。
また、ハロゲン元素とも激しく反応します。さらに、水と反応すると水素が生じ、水素を点火するために十分な量の反応熱も得られるため、爆発的に反応が進行します。
そのほか、カリウム、ナトリウム、セシウム、カルシウム、金などと合金を生成可能です。水銀に溶けると、アマルガムを形成します。
2. 天然のルビジウム
地殻中にルビジウムは、23番目に多く存在します。白榴石 (英: Leucite) 、カーナライト(英: Carnallite) 、ポルサイト(英: Pollucite) 、チンワルド雲母 (英: Zinnwaldite) のような鉱石に、酸化物として最大1%程度含まれます。リチア雲母 (英: Lepidolite) はルビジウムを0.3〜3.5%含有しているため、商用ベースのルビジウム源に使用可能です。
海水は、平均125μg/Lのルビジウムを含んでいます。同族元素と比べると、カリウムより大幅に少なく、セシウムより大幅に多いです。ルビジウムの主要な産出源は、イタリアにあるエルバ島のルビジウム微斜長石とカナダにあるバーニック湖のポルサイト鉱床です。
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解説
ルビジウム，原子番号37の元素．電子配置1s22s22p63s23p63d104s24p65s1の周期表1族アルカリ金属元素．原子量85.47．1種類の安定同位体と14種類の放射性同位体がある．天然には，非放射性の85Rb(72.165％)と放射性の87Rb(27.835％)が存在する．1861年R.W.E. Bunsen(ブンゼン)とG.R. Kirchhoffが分光分析により発見した．天然には，紅雲母(リチア雲母，鱗雲母)などの鉱石や鉱泉中に少量見いだされる．地殻中の存在度32 ppm．金属は塩化ルビジウムを真空中でカルシウムと熱し，還元すると得られる．
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主な性質
- ルビジウムの単体は銀白色の柔らかい金属であり、蒸気は青色を示す
- ルビジウムはセシウムと共に電子を放出して＋１価のイオンになりやすい
- ルビジウムは、空気に触れると直ちに酸素と結合して燃える（空気中ではごく短時間しか金属の形をしていない）
- ガラス中の炭酸ルビジウムは電気伝導性を低下させたり、安定性を増す（特殊ガラスや光学ガラス繊維に添加される）
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構造
体心立方格子構造．格子定数a ＝ 0.562 nm．金属結合半径2.47 Å．
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化学的性質
化学的性質はカルシウムに似ているが，より活性が高い．空気中でただちに酸化されて表面がくもるが，高温では超酸化物RbO2を生じる．水素，ハロゲンと直接化合する．水とはげしく反応して水素と水酸化物を生じる．水銀とアマルガムをつくり，ほかのアルカリ金属とは固溶体をつくる．化合物中ではつねに酸化数1の陽イオンとして存在する．
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生産
ルビジウム化合物は、年間2〜4トンほど生産されます。カリウムから、ルビジウムやセシウムを分離可能です。例えば、ルビジウムセシウムミョウバンから分別晶出により、純粋なルビジウムミョウバンが生成します。
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主な用途
- 光学ガラス（カメラのレンズ、光学機器部品）
- 触媒（石油化学用）
- 血液造影剤（医療）
- 電子機器部品（磁力計など）
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化学的特性
Rubidiumis a soft, silvery white metallic element. It is solid at room temperature, but melts easily at 39.3°C. Similar to the other group 1metals, rubidium reacts exothermically in water, forming corrosive rubidium hydroxide (RbOH) and hydrogen gas, Easily oxidized in air.High heat capacity and heat transfer coefficient. Soluble in acids and alcohol.
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物理的性質
Rubidium is a silvery-white lightweight solid at room temperature, but it melts at just 38.89°C (102°F), which is just over the human body's normal temperature. It's boiling point is 686°C, it's density is 1.532 g/cm3, and it has an oxidation state of +1.
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同位体
There are 30 isotopes of rubidium, ranging from Rb-75 to Rb-98. Rb-85 is theonly stable form of rubidium and constitutes 72.17% of all rubidium isotopes found inthe Earth’s crust. Rb-87 is radioactive (a half-life of 4.9×1010 years) and makes up about27.83% of the remainder of rubidium found in the Earth’s crust. All the other 28 isotopes make up a tiny fraction of all the rubidium found on Earth and are radioactive withvery short half-lives.
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名前の由来
Rubidium is named for the Latin word rubidus, meaning “reddish.
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天然物の起源
Rubidium does not exist in its elemental metallic form in nature. However, in compoundforms it is the 22nd most abundant element on Earth and, widespread over most land areasin mineral forms, is found in 310 ppm. Seawater contains only about 0.2 ppm of rubidium,which is a similar concentration to lithium. Rubidium is found in complex minerals and untilrecently was thought to be a rare metal. Rubidium is usually found combined with other Earthmetals in several ores. The lepidolite (an ore of potassium-lithium-aluminum, with traces ofrubidium) is treated with hydrochloric acid (HCl) at a high temperature, resulting in lithiumchloride that is removed, leaving a residue containing about 25% rubidium. Another processuses thermochemical reductions of lithium and cesium ores that contain small amounts ofrubidium chloride and then separate the metals by fractional distillation.
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特性
Rubidium is located between potassium and cesium in the first group in the periodic table.It is the second most electropositive alkali element and reacts vigorously and explosively in airor water. If placed on concrete on a sunny day, it would melt and then react violently withmoist air to release hydrogen with enough heat to burn the hydrogen. If a chunk of rubidiummetal is left on a table exposed to the air, it combusts spontaneously. Rubidium must be storedin oil, such as kerosene.
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使用
Because rubidium is a much larger atom than lithium or sodium, it gives up its outer valence electron easily, thus becoming a positive ion (oxidation state = Ru+). Rubidium forms numerous compounds, but only a few are useful. One of the main uses for rubidium is as a getter in vacuum tubes used in early radios, TVs, and cathode-ray tubes. When rubidium gas is placed in sealed glass cells along with an inert gas, it becomes a rubidium-gas cell clock. Because of the consistent and exact frequency (vibrations) of it atoms, it is a very accurate timekeeper. Rubidium and selenium are used in the manufacture of photoelectric cells, sometimes called electric eyes. Rubidium is a very caustic alkali (base) with a high pH value that makes it an excellent reducing agent (highly electropositive) in industry and chemical laboratories. A unique use is its ability to locate brain tumors. It is a weak radioisotope able to attach itself to diseased tissue rather than healthy tissue, thus making detection possible.
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定義
rubidium: Symbol Rb. A soft silvery white metallic element belonging togroup 1 (formerly IA) of the periodictable; a.n. 37; r.a.m. 85.47; r.d. 1.53;m.p. 38.89°C; b.p. 688°C. It is foundin a number of minerals (e.g. lepidolite)and in certain brines. The metalis obtained by electrolysis of moltenrubidium chloride. The naturally occurringisotope rubidium–87 is radioactive(see rubidium–strontiumdating). The metal is highly reactive,with properties similar to those ofother group 1 elements, ignitingspontaneously in air. It was discoveredspectroscopically by Robert Bunsenand Gustav Kirchhoff in 1861.
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製造方法
Although rubidium metals have been prepared by fused salt electrolysis, the highly reactive nature of the metals complicates the collection step and favors the use of other preparative methods where the metals can be removed in vapor form from the reaction mixture. The oxides, hydroxides, carbonates, halides, sulphates, chromates and nitrates of rubidium have been reduced to the metals by strong reducing metals such as sodium, calcium, magnesium, barium, iron, zirconium, aluminum or silicon at moderately high temperatures. The preferred method, however, involves the reduction of the anhydrous metal chlorides with calcium metal under vacuum. Anhydrous rubidium chloride is mixed with a large excess of calcium chips and heated under vacuum at 700- 800°C. As the chloride is reduced, metal vapors issue from the reaction mixture and are led under the vacuum to a cooler portion of the vessel where they condense and drop into a collection vessel.
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一般的な説明
A soft silvery metal. Shipped in very limited quantities sealed in a copper tube and over packed in a wooden box. Used in electronics.
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空気と水の反応
Tarnishes rapidly upon exposure to air. Reacts violently with water to form corrosive RUBIDIUM hydroxide and hydrogen, a flammable gas. The heat of the reaction usually ignites the hydrogen.
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反応プロフィール
RUBIDIUM METAL is a strong reducing agent. Burns spontaneously in dry oxygen [Mellor 2:468 1946-47]. Readily catches fire in air when molten or with a sulfur vapor [Mellor 2: 469 1946-47]. Causes explosive decomposition of maleic anhydride. [Chem Safety Data Sheet SD-88 1962; Chem. Haz. Info. Series C-71 1960] Burns in chlorine [Mellor 2, Supp. 1:380 1956]. Interaction with mercury is exothermic and may be violent, [Mellor, 1941, Vol. 2, 469].
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危険性
The major hazard is from fire and explosions of the elemental metallic form of rubidium.It must be stored in an inert atmosphere or in kerosene. When rubidium contacts skin, itignites and keeps burning and produces a deep, serious wound. Water and blood just make itreact more vigorously.
Many of the compounds of rubidium are toxic and strong irritants to the skin and lungs.It is one of the elements best left to experienced handlers.
Very small traces of rubidium are found in the leaves of tobacco, tea, and coffee, as well asin several edible plants, but these radiation traces are harmless when used in moderation.
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健康ハザード
Inhalation or contact with vapors, substance or decomposition products may cause severe injury or death. May produce corrosive solutions on contact with water. Fire will produce irritating, corrosive and/or toxic gases. Runoff from fire control may cause pollution.
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火災危険
Produce flammable gases on contact with water. May ignite on contact with water or moist air. Some react vigorously or explosively on contact with water. May be ignited by heat, sparks or flames. May re-ignite after fire is extinguished. Some are transported in highly flammable liquids. Runoff may create fire or explosion hazard.
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同位体
ルビジウムの同位体は、24種類知られています。天然に存在する同位体は、安定同位体の85Rbと放射性同位体の87Rbです。天然存在比は、それぞれ72.2%と27.8%です。
環境中に87Rbは広く存在します。87Rbの半減期は4.88×1010年です。87Rbはベータ崩壊によって安定な87Srに変わるため、年代測定に利用されています。
82Rbは天然には存在しませんが、82Srの崩壊によって生成します。82Rbの半減期は1.273分です。82Rbは心臓のポジトロン断層法に使用されます。
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使用用途
ルビジウムは、に添加すると、強度や電気絶縁性が高くなります。主に炭酸ルビジウム (Rb2CO3) としてガラスに混ぜられ、ブラウン管に利用可能です。
そのほか、原子時計にも使用可能です。ただし、ルビジウムの商業・工業用途は限られています。
それ以外にも、年代測定に利用されています。鉱物中などのルビジウム87と87の含有量比から、これらの物質が結晶化してから現在までの年代を算出可能です。
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安全性プロファイル
Moderately toxic by intraperitoneal route. A very reactive alkali metal (more reactive than potassium or cesium). In the body, rubidlum substitutes for potassium as an intracellular ion. The ratio of Rb/K intake is important in the toxicology of rubidium. A ratio above 40% is dangerous. In rats, a failure to gain weight is the first symptom, followed by ataxia and hyperirritabhty. Symptoms include: skin ulcers, poor hair coat, sensitivity, and extreme nervousness leading to convulsions and death.
hazard when exposed to heat or flame or by chemical reaction with oxidlzers. Igmtes on contact with air, oxygen, and halogens. A very dangerous fire and explosion
RUBIDIUM HYDROXIDE RPZOOO 121 5
Ignites spontaneously on contact with water. Reaction with water, moisture, or steam forms explosive hydrogen gas, whch then ignites. Explodes in contact with liquid bromine. Can react explosively with air, halogens, mercury, nonmetals, vanadium chloride oxide, moisture, acids, oxidizers. Violent reaction with vanadium trichloride oxide (at 60℃C), Cl202, P. Molten rubidium ignites in sulfur vapor and reacts vigorously with carbon. RbOH is more basic than KOH. Storage and handling: Keep under benzene, petroleum, or other liquids not containing gaseous O2. When heated to decomposition it emits toxic fumes of RbzO. See also SODIUM and SODIUM POTASSIUM ALLOY.
