リチウム

外観

銀白色～灰褐色、粒状

歴史

リチウムを含む鉱石、葉長石とリチア輝石は、1790年から1800年にかけて、スウェーデンのウテUtö島でアンドラダJose de Andradaによって発見されている。この葉長石の中に新しいアルカリ金属元素が含まれていることをみいだしたのはスウェーデンのアルフェドソンJohan August Arfvedson（1792―1841）で、1817年であった。リチウムの名は、ギリシア語の石lithosにちなんで、アルフェドソンの指導者ベルツェリウスによって提案された。ナトリウムやカリウムが植物関連物質からみいだされたのに対し、リチウムが鉱石からみいだされたことに基づいている。1818年W・TブランデBrandéとH・デービーは酸化リチウムを電解して少量のリチウム金属を単離しているが、物性の測定ができるほどの量を初めて得たのは、ドイツのブンゼンとイギリスのマチーセンAugustus Mathiessen（1831―1870）で、塩化リチウムの融解電解によって1855年に成功している。［鳥居泰男］

主な性質

1. 全ての金属の中で一番軽く、水に浮く銀白色の金属（大気中では黒色の錆びを生成する）

2. リチウムは液体で存在する温度領域が極めて広い。融点と沸点が１，２００℃近くも離れている

3. イオン化傾向が最も大きく、電気化学的に最も卑な金属である

4. 常温での反応性には、アルカリ金属に属するにもかかわらず·窒素と反応する ·水と穏やかに反応する ·炭化物を作る·化合物の水への溶解度はマグネシウムに類似する、など特異な性質である

5. 溶融状態の金属リチウムは極めて活性であり、水とは爆発的に反応し、多くの金属や耐火物を激しく侵す

6. リチウムは中性子吸収断面積が大きく、遅い中性子の放射を受けるとトリウムを発生する

7. アルミニウムーリチウム合金は、低比重、高剛性が特徴で、高速回転や航空機材に使われる

存在

リチウムは，岩石や天然水の中に微量ではあるが広く分布している。動植物界たとえば海藻、タバコ、コーヒー、牛乳、血液などにも存在が認められる。工業資源として重要な鉱石はリチア輝石AlLi(SiO3)2、紅雲母(うんも)AlKLi2(FeOH)2(Si4O10)、葉長石AlLi(Si2O5)2、アンブリゴ石AlPO4・LiFなどである。天然塩水で数百ppmを含むものがアメリカのカリフォルニア州、ネバダ州などでみいだされており、資源として注目される。

溶解性

水及び希塩酸に溶ける。水と激しく反応して、水素を発生し水酸化リチウムになるが、その反応性はアルカリ金属の中では最も穏やかである。

解説

Li．原子番号3の元素．電子配置1s22s1の周期表1族元素．原子量6.94．安定同位体 6Li，7Li，ほかに3種類の放射性同位体がある．1817年J. Berzelius(ベルセリウス)の弟子J.A. Arfwedsonがペタル石(petalite，LiAlSi4O10)中に発見し，Berzeliusがギリシア語の岩石λιθοζ"(lithos)から命名した．宇田川榕菴は天保8年(1837年)出版の「舎密開宗」で，利知烏母(リチウム)と記載している．1855年R.W.E. Bunsen(ブンゼン)とA. Mathiessenが塩化物の融解電解によりはじめて金属を遊離した．天然には，リチア雲母，ペダル石，リチア石などの鉱石や岩石中に広く分布する．地殻中の存在度13 ppm．最大資源国はボリビアで推定埋蔵量540万t．次いでチリ300万t．おもに炭酸リチウムとして輸入され，2006年度の輸入量は14000 t で，約1万t がチリから．塩化リチウムの融解電解で得られる．真空蒸留により精製する．銀白色の軟らかい金属．体心立方格子構造．格子定数a ＝ 0.350 nm(20 ℃)．融点180.5 ℃，沸点1350 ℃．密度0.534 g cm－3(20 ℃)．第一イオン化エネルギー5.390 eV．炎色反応は深紅色．常温，乾いた空気中では酸化されない．高温では酸素，窒素，水素，ハロゲン，硫黄，炭素，ケイ素などと直接化合する．常温の水や酸と反応して水素を発生し，水酸化物や塩を生じる．化合物においてはつねに酸化数1をとる．リチウムやリチウム化合物の化学的性質は，マグネシウムに似ている点が多い．これは Li＋ が Mg2＋ とほぼ同じ大きさをもつためである．重合触媒(アルミニウム-リチウム合金)，合金添加物，リチウムイオン電池用電極材，半導体材料，脱酸剤として用いられる．リチウムイオン電池用が最大·最重要用途である．森北出版「化学辞典（第2版）

用途

金属還元剤·合金添加·リチウム電池

製法

原鉱を硫酸、炭酸ナトリウム、塩酸などで処理して塩化リチウムとし、これに塩化カリウムを加えて融解電解することによって製造される。ピリジン、エタノール（エチルアルコール）、アセトンなどの中で塩化リチウムを電解する方法も行われる。

性質と用途

銀白色の軟らかい金属で、全金属元素中もっとも軽い。アルカリ金属元素の典型的な性質をもっていると同時に、ナトリウム以下とはかなり異なった性格を示し、むしろ、周期表で対角関係にあるマグネシウムに似た点も多い。乾燥空気中では安定でほとんど酸化されないが、熱すれば強い光を放って反応し酸化物Li2Oを与える（一般のアルカリ金属は過酸化物、超酸化物を与える）。

4Li+O2→2Li2O

2Li+2H2O→2LiOH+H2

金属として原子炉材料、有機合成の重合触媒などに用いられるほか、各種合金の添加剤、鋼材、合金の脱酸剤などとして最近その重要性が増している。

効能

躁病薬

主な用途

2. 航空機部材（Al－Li合金）

4. ブラウン管（テレビ、パソコンモニター）

6. 弾性表面フィルター（テレビ、携帯電話など）

8. リチウムイオン電池正極材（２次電池）

10. 水冷媒吸収剤（吸収式冷凍機）

12. 溶接用フラックス（溶接棒）

14. 除湿材（空調機）

16. 耐熱ガラス、陶磁器うわぐすり（耐熱ガラス製品）

18. 合成ゴム重合触媒（合成ゴム製造用）

20. グリース（潤滑材）

22. 電解質（リチウム·イオン電池など、１次、２次電池）

使用上の注意

不活性ガス封入

説明

Lithium is an alkali metal with physiologic actions similar to potassium and sodium. Lithium was discovered as a salt in 1817 by Johan August Arfwedson. It does not occur in nature as a free metal but is found in minerals such as spodumene, petalite, and eucryptite. It is the 27th most abundant element in Earth’s crust. Lithium was used to treat gout, as a salt substitute, and as a major constituent of the soft drink 7-Up before 1950.

化学的特性

Lithium is a silvery to grayish-white metal that turns yellow on exposure to air and/or moisture.

物理的性質

In the metallic state, lithium is a very soft metal with a density of 0.534 g/cm³. When asmall piece is placed on water, it will float as it reacts with the water, releasing hydrogen gas.Lithium’s melting point is 179°C, and it has about the same heat capacity as water, with aboiling point of 1,342°C. It is electropositive with an oxidation state of +1, and it is an excellent conductor of heat and electricity. Its atom is the smallest of the alkali earth metals andthus is the least reactive because its valence electron is in the K shell, which is held closest toits nuclei.

同位体

There are two stable lithium isotopes: Li-6.015, which makes up 7.5% of all lithium atoms, and Li-7.016, which makes up 92.5% of lithium atoms found in the Earth’scrust. Less prevalent isotopes of lithium are Li-4, Li-5, Li-8, Li-9, Li-10, and Li-11. Theyare unstable with short half-lives and make up only a very small fraction of Lithium’stotal averaged atomic weight.

名前の由来

The name lithium comes from the Greek word lithos, meaning “stone” because it was found in rocks on Earth.

天然物の起源

Lithium ranks 33rd among the most abundant elements found on Earth. It does not existin pure metallic form in nature because it reacts with water and air. It is always combinedwith other elements in compound forms. These lithium mineral ores make up only about0.0007%, or about 65 ppm, of the Earth’s crust.Lithium is contained in minute amounts in the mineral ores of spodumene, lepidolite, andamblygonite, which are found in the United States and several countries in Europe, Africa, andSouth America. High temperatures are required to extract lithium from its compounds and byelectrolysis of lithium chloride. It is also concentrated by solar evaporation of salt brine in lakes.Metallic lithium is produced on a commercial scale by electrolysis of molten lithium chloride (LiCl) that is heated as a mixture with potassium chloride (KCl). Both have a rather highmelting point, but when mixed, the temperature required to melt them (400°C) is severalhundred degrees lower than their individual melting points. This liquid mixture of LiCl andKCl becomes the electrolyte. The anode is graphite (carbon) and the cathode is steel. Themolten liquid positive lithium cations collect at the cathode while negative chlorine anionscollect at the anode, and the potassium chloride remains in the electrolyte. Each positive ion oflithium that collects at the cathode gains an electron, thus producing neutral atoms of moltenlithium metal, which is then further purified.

特性

While classified as an alkali metal, lithium also exhibits some properties of the alkali earthmetals found in group 2 (IIA). Lithium is the lightest in weight and softest of all the metalsand is the third lightest of all substances listed on the periodic table, with an average atomicweight of about 7. (The other two are hydrogen and helium.) Although it will float on water,it reacts with water, liberating explosive hydrogen gas and lithium hydroxide (2Li + 2H₂O →2LiOH + H₂?). It will also ignite when exposed to oxygen in moist air (4Li + O₂ → 2Li₂O).It is electropositive and thus an excellent reducing agent because it readily gives up electrons inchemical reactions. Lithium is the only metal that reacts with nitrogen at room temperature.When a small piece of the metal, which is usually stored in oil or kerosene, is cut, the newsurface has a bright, shiny, silvery surface that soon turns gray from oxidation.

使用

In production of organometallic alkyl and aryl lithium compounds; in production of high-strength, low-density aluminum alloys for the aircraft industry; extremely tough, low-density alloys with aluminum and magnesium used for armour plate and aerospace components. In polymerization catalysts for the polyolefin plastics industry; manufacture of high-strength glass and glass-ceramics. As anode in electrochemical cells and batteries; as chemical intermediate in organic syntheses. Lithium stearate as thickener and gelling agent to transform oils into lubricating greases.

生物学の機能

For more than 40 years, Li⁺ has been used to treat mania. While it is relatively inert in individuals without a mood disorder, lithium carbonate is effective in 60 to 80% of all acute manic episodes within 5 to 21 days of beginning treatment. Because of its delayed onset of action in the manic patient, Li⁺ is often used in conjunction with low doses of high-potency anxiolytics (e.g., lorazepam) and antipsychotics (e.g. haloperidol) to stabilize the behavior of the patient. Over time, increased therapeutic responses to Li⁺ allow for a gradual reduction in the amount of anxiolytic or neuroleptic required, so that eventually Li⁺ is the sole agent used to maintain control of the mood disturbance.
In addition to its acute actions, Li⁺ can reduce the frequency of manic or depressive episodes in the bipolar patient and therefore is considered a mood-stabilizing agent. Accordingly, patients with bipolar disorder are often maintained on low stabilizing doses of Li⁺ indefinitely as a prophylaxis to future mood disturbances. Antidepressant medications are required in addition to Li⁺ for the treatment of breakthrough depression.

一般的な説明

A soft silvery metal that is normally grayish white due to oxide formation. Spontaneous ignition is likely if heated to melting point.

空気と水の反応

Highly flammable. Is readily ignited by and reacts with most extinguishing agents such as water, carbon dioxide, and carbon tetrachloride [Mellor 2, Supp 2:71. 1961]. Reacts with water to form caustic Litium hydroxide and hydrogen gas (H2). Litium is spontaneously flammable in air if heated to 180°C if the surface of the metal is clean.

反応プロフィール

Burns in air, oxygen, nitrogen, hydrogen, and carbon dioxide. The reactions can become extremely violent at higher temperatures. The disposition to ignite of surfaces of molten Litium exposed to any of these gases is increased by the presence of Litium oxides and nitrides. Litium reacts avidly with water to generate gaseous hydrogen and a solution of Litium hydroxide (a caustic). Contact with halogenated hydrocarbons can produce extremely violent reactions, especially on impact [Haz. Chem. Data 1966]. Boron trifluoride reacts with incandescence when heated with Litium [Merck 11th ed. 1989]. Maleic anhydride decomposes explosively in the presence of Litium [Chemical Safety Data Sheet SD-88. 1962, Chem. Haz. Info. Series C-71. 1960]. Chlorine vapors and Litium react producing a luminous flame [Mellor 2, Supp. 1:380. 1956]. The product of the reaction between Litium and carbon monoxide, Litium carbonyl, detonates violently with water, igniting the gaseous products [Mellor 2, Supp. 2:84. 1961]. The reaction of Litium and ferrous sulfide starts around 260°C with subsequent rise in temperature to 950° C [Mellor 2, Supp. 2:80. 1961]. A truck, which was carrying Litium batteries, sodium dithionite and derivatives of cyanide, caught fire; multiple explosions occurred as the cargo was exposed to the air.

危険性

Lithium metal is highly flammable, explosive, and toxic. It will ignite when exposed towater, acids, and even damp air. Metallic lithium is a reducing agent that readily gives up anelectron to active oxidizing agents that require an electron to complete their outer valenceshell—thus the violent chemical reaction that follows. Lithium will even burn in nitrogengas, which is relatively stable. In addition, many of its compounds also react violently whenexposed to water.
As an element (metal), it must be stored in oil or in some type of air and moisture-free container,given that many of its compounds will also burn when exposed to air or water. Lithiumfires are difficult to extinguish. If water is poured on the fire, lithium will just burn faster orexplode. A supply of special chemicals or even dry sand is required to extinguish such fires.
Solutions and powders of several lithium salts are very toxic to the human nervous system,thus requiring close observation by a physician when used as antidepressant drugs.

健康ハザード

Lithium can react with moisture on the skinto produce corrosive hydroxide. Thus, contactof this metal with the skin or eyes can causeburn. The fumes are irritating to the skin,eyes, and mucous membranes. Ingestion of lithium can cause kidney injury, especiallywhen sodium intake is limited (Merck 1996).

火災危険

Lithium is less active than sodium or potassium. Finely divided metal ignites spontaneously in air. The ignition of the bulk metal occurs when heated to its melting point. It burns with a carmine-red flame. Burning evolves dense white and opaque fumes. Vigorous reaction occurs when the metal is mixed with water. The heat of reaction, if not dissipated, can ignite or explode hydrogen that is liberated.
Violent explosive reactions occur with carbon tetrachloride; carbon tetrabromide; chloroform, bromoform, or iodoform (on heating); carbon monoxide in the presence of water; phosphorus (on heating); arsenic (on heating); and sulfur (molten). Among the substances that constitute high explosion hazards, the halogenated hydrocarbons are most significant. A number of compounds of this class in addition to those mentioned above form impact-sensitive products that can detonate on heating or impact.
Heating with nitric acid can cause fires. Lithium reacts with nitrogen at elevated temperatures to form lithium nitride, which can ignite on heating.

応用例（製薬）

Lithium inhibits GSK-3 and InsP, and both pathways have therefore been suggested to be involved in the treatment of BD and schizophrenia. The theory behind this hypothesis is that overactive InsP signalling in the brain of these patients potentially causes BD and this may be reduced by the inhibitory effect of lithium on such signalling.
It is believed that lithium potentially can protect against disease-induced cell death. GSK-3 has been implicated in the origins of schizophrenia, but with the availability of many antipsychotic drugs on the market, lithium ions are not in common use for the treatment of schizophrenia. There are also several direct roles of lithium in the treatment of Alzheimer’s disease. Alzheimer’s disease is a neurodegenerative brain disorder causing neuronal dysfunction and ultimately cell death.
Onset occurs with the accumulation of extracellular senile plaques composed of amyloid-β peptides and with the accumulation of intercellular neurofibrillary tangles.

工業用途

This lightest of all metals is found in more than 40 minerals, but is obtained chiefly from lepidolite, spodumene, and salt brines.
It is unstable chemically and burns in the air with a dazzling white flame when heated to just above its melting point. The metal is silvery white but tarnishes quickly in the air. The metal is kept submerged in kerosene. Lithium resembles sodium, barium, and potassium, but has a wider reactive power than the other alkali metals. It combines easily with oxygen, nitrogen, and sulfur to form low melting-point compounds that pass off as gases, and is thus useful as a deoxidizer and degasifier of metals.

副作用

The frequency and severity of adverse reactions associated with Li⁺ therapy are directly related to serum levels Since Li⁺ has a low therapeutic index (approximately 3) and a narrow therapeutic window (0.5–1.5 mEq/L), the frequent measurement of serum steadystate concentrations is standard practice in the treatment of bipolar patients.
Adverse reactions occurring at serum trough levels (12 hours after the last dose) below 1.5 mEq/L are generally mild, whereas those seen above 2.5 mEq/L are usually quite severe. Mild toxicity is usually expressed as nausea, vomiting, abdominal pain, diarrhea, polyuria, sedation, and fine tremor. If the serum concentration of Li⁺ progressively rises above 2 mEq/L, frank neurological toxicity appears, beginning with mental confusion and progressing to hyperreflexia, gross tremor, dysarthria, focal neurological signs, seizures, progressive coma, and even death.
Adverse effects sometimes seen during chronic maintenance of bipolar patients with Li⁺ include hypothyroidism (approximately 5%) and nephrogenic dia-betes insipidus.Both conditions are readily reversible by discontinuation of Li⁺. Routine laboratory monitoring includes TSH (thyroid-stimulating hormone) and serum creatinine measurements to detect hypothyroidism and any change in renal capacity to clear the drug.

職業ばく露

Lithium is used in inorganic syntheses; the manufacture of storage batteries; heat transfer liquids; and metal alloys.

特性

・金属中で最も軽い
・大気中で酸化されやすい
・ナトリウムに次いでやわら かいが、延性は乏しい
・ガラスや金属、コンクリート などに添加すると、物性を 著しく改善する

用途

軽くて大容量の電池として活躍
金属中最も軽く、イオン化傾向が大きいというエネルギー密度を活 かし、リチウムイオン電池（以下 LIB）は自動車のバッテリーやノートパ ソコンなどのモバイル用電源として欠かせない存在であり、電気自動 車(EV)の販売増を背景に需要が拡大している。大気中で容易に酸化 されるため、主に軽量合金として利用されてきたが、リチウム金属及び その化合物の用途は、電池以外でも耐熱ガラスなどのガラス用添加 剤、冷凍機の吸収剤などでも需要が増大し、また、アルミ・リチウム合 金は航空機の構造材としても使用されている。

環境運命予測

Lithium is a soft, silver-white metal that is highly reactive and flammable. It is typically stored in mineral oil. Lithium concentrations in the earth’s crust are estimated to be 20–70 ppm by weight. Lithium is widely distributed in nature. Some trace amounts can be found in many minerals, rocks, and soils and in many natural water sources. In air, lithium compounds exist as particulate but their ionic nature makes them nonvolatile and may be removed by wet and dry deposition. In soil, lithium compounds are expected to adsorb moderately to soils and sediments. A lithium ion would not undergo oxidation–reduction reactions and exists in its +1 oxidation or dissolved ions. Lithium ions may undergo precipitation, sorption, or ligand exchange reactions. In water, lithium compounds are not expected to adsorb to suspended solids and sediments. Volatilization and bioconcentration are insignificant.
Concentrations of lithium in surface waters are typically very low (<0.04 mg l^-1). Seepage into ground water and surface water from storage sites (e.g., the US Department of Energy’s Y^-12 plant) may lead to concentration much higher (0.15 mg l^-1).

輸送方法

UN1415 Lithium, Hazard Class: 4.3; Labels: 4.3-Dangerous when wet material. UN3089 Metal powders, flammable, n.o.s., Hazard Class: 4.1; Labels: 4.1- Flammable solid

純化方法

After washing with pet ether to remove storage oil, lithium is fused at 400o and then forced through a 10-micron stainless-steel filter with argon pressure. It is again melted in a dry-box, skimmed, and poured into an iron distillation pot. After heating under a vacuum to 500o, cooling and returning it to the dry-box for a further cleaning of its surface, the lithium is distilled at 600o using an all-iron distillation apparatus [Gunn & Green J Am Chem Soc 80 4782 1958].

不和合性

Violent reaction with water, forming flammable hydrogen gas and corrosive lithium hydroxide, a strong caustic solution. Heating may cause violent combustion or explosion. Finely divided particles or powdered form may ignite spontaneously in air. Contact with air forms corrosive fumes of lithium hydroxide. Violent reaction with oxidizers, acetonitrile, nitric acid; arsenic, bromobenzene, carbon tetrachloride; hydrocarbons, halogens, halons, sulfur, and many other substances. Forms impactand friction-sensitive mixtures with bromobenzene, carbon tetrabromide, chloroform (weak explosion), iodoform, halogens, halocarbons, methyl dichloride; methyl diiodide and other substances. Attacks plastics, rubber, ceramic materials; concrete, sand, and metal alloys: cobalt, iron, manganese, nickel