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리튬 C화학적 특성, 용도, 생산

개요

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.

화학적 성질

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

물리적 성질

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.

Isotopes

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.

Origin of Name

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

출처

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.

Characteristics

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.

용도

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.

Biological Functions

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.

일반 설명

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

공기와 물의 반응

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.

반응 프로필

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.

위험도

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.

건강위험

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).

화재위험

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.

Pharmaceutical Applications

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.

공업 용도

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.

부작용

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.

잠재적 노출

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

환경귀착

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).

운송 방법

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

Purification Methods

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].

비 호환성

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

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