バリウム 化学特性,用途語,生産方法
歴史
今日、重晶石bariteとよばれる硫酸バリウムの鉱石は、17世紀初めイタリアのボローニャで発見されている。比重4.5で、通常塩類の鉱石の2倍ぐらい重いので、「重い」のギリシア語barysにちなんで名づけられた。一方、スウェーデンのK・W・シェーレは1774年に、軟マンガン鉱MnO2の中に酸化バリウム（barytaとよばれた）が含まれることをみいだしている。1808年、イギリスのH・デービーは、酸化水銀と酸化バリウムの湿った混合物を電解してバリウムのアマルガムを得、蒸留によって水銀を除去して金属バリウムを単離することに成功した。水銀をまったく含まない純粋なものは、1901年、ガンツA. A. Guntzによって水素化バリウムの熱分解を通して初めて得られた。元素としての名称バリウムは、バライトbariteあるいはバライタbarytaの成分であることに由来している。
性質
銀白色の軟らかい金属で、体心立方格子の構造をとる。アルカリ土類金属中でもっとも高い沸点をもっている。化学的性質はカルシウム、ストロンチウムとよく類似しているが、それらよりは活性である。空気中で熱すれば燃焼して酸化バリウムと少量の過酸化バリウムを生ずる。窒素に対する親和力はアルカリ土類金属元素中もっとも大きく、空気中の燃焼生成物にもかならず窒化物が含まれる。純粋な窒素気流中で熱すればBa3N2の組成の窒化物が生成する。加熱により水素と直接化合し、かなり安定な水素化物BaH2を与える。水と激しく反応して水酸化バリウムを与え、水素を発生する。また、アルコールとも反応し、バリウムアルコラートを生ずる。
Ba+2H2O→Ba(OH)2+H2
Ba+2C2H5OH→Ba(C2H5O)2+H2黄緑色の炎色反応を示す。
製法
金属バリウムを電解法で直接的に得ることは困難であるので、主として蒸留冶金(やきん)によって製造される。すなわち、酸化バリウムを真空中約1200℃でアルミニウムやフェロシリコンで還元する。バリウムは蒸気となって出てくるので、これを冷却、凝縮させ、アルゴン気流中で再溶融する。塩化バリウムの水溶液を電解する方法もあるが、この場合でも陰極に水銀を用い、アマルガムの形で取り出す。これを減圧蒸留して大部分の水銀を除去したのち、水素気流中で加熱して水素化バリウムに変え、これを加熱分解して純粋な金属を得る。
主な性質
- バリウムは最も重いアルカリ土類金属で性質はカルシウムやストロンチウムに似る（反応性はそれよりも強い）
- 空気中では常温でも表面が酸化される（高温では酸化バリウムと窒化バリウムを生ずる）。水と激しく反応し水素を発生して溶ける
解説
Ba．原子番号56の元素．電子配置1s22s22p63s23p63d104s24p64d105s25p66s2の周期表2族元素．原子量137.33．7種の安定同位体(138Ba，137Ba，136Ba，135Ba，134Ba，132Ba，130Ba)と13種の放射性同位体が知られている．1809年H. Davy(デイビー)が電解によりアマルガムとして得たが，1901年A.A. Guntzにより水素化バリウムを分解してはじめて金属が遊離された．1774年K.W. Scheele(シェーレ)は鉱物BaSO4を“Schwerspaterde”とよんだが，密度の高いことからギリシア語の“重い”βαρυζ (barys)からbaryte(日本語名：重晶石)と名称がかわり，Davy提案の元素名bariumのもととなった．天然には，重晶石BaSO4，毒重石BaCO3などの形で産出する．地殻中の存在度250 ppm．酸化バリウムをアルミニウムで真空中1200 ℃ で還元すると得られる．銀白色の軟らかい金属．体心立方格子構造．格子定数a ＝ 0.501 nm．密度3.5 g cm－3(20 ℃)．融点725 ℃，沸点1640 ℃．炎色反応は緑色．化学的性質はカルシウム，ストロンチウムに似るが作用はよりはげしい．水とはげしく反応して水素と水酸化バリウムを生じる．高温では水素，酸素，窒素と直接化合する．またハロゲン，炭素，ケイ素，ホウ素とも直接化合する．二酸化炭素とは高温で反応し炭素と炭化物を生じる．高温ではガラス，磁器を侵す．酸と反応して水素を発生し，その酸の塩を生じる．バリウムイオンは体内で有毒である．金属の脱酸剤，特殊合金として真空管のゲッター，車両用の軸受などに用いられる．化合物中ではつねに酸化数2の陽イオンとして存在する．おもな化合物には，水素化物，ハロゲン化物，水酸化物，酸化物，過酸化物，過塩素酸塩，硫酸塩，炭酸塩，硝酸塩などがあり，一般に無色のイオン結晶で，水に難溶のものが少なくない．硫酸塩は水に難溶で Ba2＋ の検出や定量分析に利用され，クロム酸塩，シュウ酸塩，炭酸塩も水に難溶．硫酸塩以外は酸に溶ける．可溶性の塩は潮解性も吸湿性もない．
森北出版「化学辞典（第2版）
用途
アルミニウムまたはマグネシウムの合金として真空管のゲッターに、ニッケルの合金として自動車の点火栓に、またカルシウム‐鉛の合金として車両用の軸受に使用される。なお、バリウムイオンは生体内では有毒であるから取扱いに注意を要する。また、X線造影剤として用いられるバリウム塩は硫酸バリウムである。
主な用途
- 管球光学ガラス（テレビブラウン管、パソコンモニター）
- コンデンサ、フェライト
- 塗料、顔料用増量材（インク、塗料、顔料）
- 印刷インキ（配合剤）
- ゴム充填材（食料用白色ゴム）
- 摩擦材（自動車用ブレーキパッド）
化学的特性
Barium is a silvery-white metal. It exists in nature only in ores containing mixtures of elements. The important combinations are peroxide, chloride, sulfate, carbonate, nitrate, and chlorate. The pure metal oxidizes readily and reacts with water, emitting hydrogen. It combines with other chemicals such as sulfur or carbon and oxygen to form barium compounds. Barium compounds are used by the oil and gas industries to make drilling muds. Barium attacks most metals with the formation of alloys; iron is the most resistant to alloy formation. Barium forms alloys and intermetallic compounds with lead, potassium, platinum, magnesium, silicon, zinc, aluminum, and mercury. Barium compounds exhibit close relation-ships with the compounds of calcium and strontium, which are also alkaline earth metals. Doctors sometimes use barium sulfate to perform medical tests and to take x-rays of the gastrointestinal tract. Twentyive barium isotopes have been identii ed. 138Ba is the most abundant; the others are unstable isotopes with half-lives ranging from 12.8 days for 140Ba to 12 sec for 143Ba. Two of these isotopes, 131Ba and 139Ba, are used in research as radioactive tracers. The general population is exposed to barium through air, drinking water, and food.
物理的性質
Barium is the fifth element in group 2 (IIA) of the alkali earth metals and has most of theproperties and characteristics of the other alkali earth metals in this group. For example, theyall are called alkaline earths because, when first discovered, they exhibited both characteristicsof alkaline (basic) substances and characteristics of the earth from which they came. Ancienthumans did not know they were metals because their metallic forms do not exist in nature.Barium is a silvery metal that is somewhat malleable and machineable (can be worked on alathe, stretched and pounded). Its melting point is 725°C, its boiling point is about 1640°C,and its density is 3.51 g/cm
3. (The accurate figures for its properties are difficult to determinebecause of barium’s extreme activity—the pure metal will ignite when exposed to air, water,ammonia, oxygen, and the halogens.
同位体
Naturally occurring barium is a mixture of seven stable isotopes: barium-138 (71.66%), barium-137 (11.32%), barium-136 (7.81%), barium-135 (6.59%), barium-134 (2.42%), barium-130 (0.101%), and barium- 132 (0.097%). About six times this many radioactive isotopes have been prepared with mass numbers ranging from 114 to 153. Of the 40 isotopes known, most are highly radioactive and have half-lives in the several milliseconds to a few days range. The only notable exceptions are
133Ba with a half-life of 10.51 years,
128Ba (2.43 days),
141Ba (11.50 days) and
140Ba (12.75 days).
名前の由来
The name barium is derived from the Latin word barys, which means
“heavy.
天然物の起源
Barium is the 17th most abundant element in the Earth’s crust, making up about 0.05%of the crust. It is found in the minerals witherite, which is barium carbonate (BaCO
3), andbarite, known as barium sulfate (BaSO
4). Pure barium metal does not exist on Earth—only ascompounds or in minerals and ores. Barium ores are found in Missouri, Arkansas, Georgia,Kentucky, Nevada, California, Canada, and Mexico.It is produced by the reduction of barium oxide (BaO), using aluminum or silicon ina high-temperature vacuum. It is also commercially produced by the electrolysis of moltenbarium chloride (BaCl
2) at about 950oC, wherein the barium metal is collected at the cathodeand chlorine gas is emitted at the anode.
特性
When barium burns in air, it produces barium oxide (2Ba + O
2 → 2BaO). When metallicbarium burns in water, it forms barium hydroxide [Ba + 2H
2O → Ba(OH)
2 + H
2↑]. Severalbarium compounds burn with a bright green flame, which make them useful for fireworks.Barium is more reactive with water than are calcium and strontium. This is a result of thevalence electrons’ being further from the positive nucleus. Therefore, barium is more electronegative than the alkali earth metals with smaller nuclei.In powdered form, it will burst into a bright green flame at room temperature.
使用
Pure barium metal has few commercial uses because of it reactivity with air and water.Nevertheless, this property makes it useful as a “getter” or scavenger to remove the last tracesof gas from vacuum tubes. Barium metal is used to form alloys with other metals. One alloy isused to make sparkplugs that easily emit electrons when heated, thus improving the efficiencyof internal combustion engines.Its compounds have many practical uses. For example, when the mineral barite is groundup into a fine powder, it can be used as a filler and brightener for writing and computer paper.It is also used (along with zinc sulfide) as a pigment, called lithopone, for white paint. Bariumcompounds are also used in the manufacture of plastics, rubber, resins, ceramics, rocket fuel,fireworks, insecticides, and fungicides and to refine vegetable oils.A major medical use is a solution of barium sulfide (with flavoring) that is ingested bypatients undergoing stomach and intestinal X-ray and CT scan examinations. Barium sulfideis opaque to X-rays, and thus it blocks the transmission of the rays. The organs appear in contrast against a background, which highlights any problems with the digestive system.
定義
A dense, low-melting reactive metal; the fifth member of group 2 (formerly IIA) of the periodic table and a typical alkaline-earth element. The electronic configuration is that of xenon with two additional outer 6s electrons. Barium is of low abundance; it is found as witherite (BaCO3) and barytes (BaSO4). The metal is obtained by the electrolysis of the fused chloride using a cooled cathode which is slowly withdrawn from the melt. Because of its low melting point barium is readily purified by vacuum distillation. Barium metal is used as a ‘getter’, i.e., a compound added to a system to seek out the last traces of oxygen; and as an alloy constituent for certain bearing metals.
Barium has a low ionization potential and a large radius. It is therefore strongly electropositive and its properties, and those of its compounds, are very similar to those of the other alkaline-earth elements calcium and strontium.
一般的な説明
Barium alloy, pyrophoric is mixture of barium and other metals or nonmetallic elements to improve the specific usefulness of barium. Barium alloys are a solid and can ignite spontaneously in contact with air. Barium is toxic and products given off in fire could be very toxic.
空気と水の反応
Finely divided metal powder is pyrophoric, ignites spontaneously in air [Bretherick 1979 p. 170-171]. Alloys containing a substantial proportion of barium rapidly decomposed water. The heat of the reaction is sufficient that the evolved hydrogen may ignite [Lab. Govt. Chemist 1965].
反応プロフィール
Alloys containing a substantial amount of barium react violently with acids [Lab. Gov. Chemist 1965].
危険性
Barium metal, in powder form, is flammable at room temperature. It must be stored in anoxygen-free atmosphere or in petroleum.
Many of barium’s compounds are toxic, especially barium chloride, which affects the functioningof the heart, causing ventricular fibrillation, an erratic heartbeat that can lead to death.Several of barium’s compounds are explosive as well as toxic if ingested or inhaled. Care shouldbe used when working with barium and other alkali metals in the laboratory or in industry.
火災危険
Flammable/combustible material. May ignite on contact with moist air or moisture. May burn rapidly with flare-burning effect. Some react vigorously or explosively on contact with water. Some may decompose explosively when heated or involved in a fire. May re-ignite after fire is extinguished. Runoff may create fire or explosion hazard. Containers may explode when heated.
工業用途
Barium (symbol Ba) is a metallic element thatoccurs in combination in the minerals witheriteand barite, which are widely distributed. Themetal is silvery white in color and can beobtained by electrolysis from the chloride, butit oxidizes so easily that it is difficult to obtainin the metallic state. Its melting point is 850°C,and its specific gravity 3.78. The most extensiveuse of barium is in the form of its compounds.The salts that are soluble, such as sulfide andchloride, are toxic. An insoluble, nontoxic bariumsulfate salt is used in radiography. Bariumcompounds are used as pigments, in chemicalmanufacturing, and in deoxidizing alloys of tin, copper, lead, and zinc. Barium is introducedinto lead-bearing metals by electrolysis toharden the lead.Barium is also a key ingredient in ceramicsuperconductors.
安全性プロファイル
Water and stomach
acids solubilize barium salts and can cause
poisoning. Symptoms are vomiting, colic,
diarrhea, slow irregular pulse, transient
hypertension, and convulsive tremors and
muscular paralysis. Death may occur in a
few hours to a few days. Half-life of barium
in bone has been estimated at 50 days. Dust
is dangerous and explosive when exposed to
heat, flame, or chemical reaction. Violent or
explosive reaction with water, CCh,
fluorotrichloromethane, trichloroethylene,
and C2Cl4. Incompatible with acids, C2CLF3,
C2H2FCl3, C2HCl3 and water, 1,1,2-
trichlorotrifluoroethane, and
fluorotrichloroethane. The powder may
ignite or explode in air or other oxidizing
gases. See also BARIUM COMPOUNDS.
職業ばく露
Metallic barium is used for removal of
residual gas in vacuum tubes and in alloys with nickel, lead,
calcium, magnesium, sodium, and lithium. Barium compounds
are used in the manufacture of lithopone (a white
pigment in paints), chlorine, sodium hydroxide, valves, and
green flares; in synthetic rubber vulcanization; X-ray diagnostic
work, glassmaking, papermaking, beet-sugar purification;
animal and vegetable oil refining. They are used in the
brick and tile, pyrotechnics, and electronics industries. They
are found in lubricants, pesticides, glazes, textile dyes and
finishes; pharmaceuticals; in cements which will be exposed
to saltwater; and barium is used as a rodenticide, a flux for
magnesium alloys, a stabilizer and mold lubricant in the rubber
and plastics industries, an extender in paints; a loader for
paper, soap, rubber, and linoleum; and as a fire extinguisher
for uranium or plutonium fires.
導入
バリウムはアルカリ土類金属のひとつである。単体では銀白色の柔らかい金属である。空気中では酸化され酸化被膜に覆われる。化学的性質はカルシウムやストロンチウムに似ているが、バリウムの方が、反応性が高い。バリウム塩類は、他のアルカリ土類よりも水に対する溶解度が低く、また熱的安定性に優れている。
特性
・アルカリ土類金属
・単体では銀白色の柔らかい
金属。空気中では酸化され酸
化被膜に覆われる。
・バリウム塩は、他のアルカリ
土類よりも水の溶解度が低く
熱的安定性が優れる。
用途
積層セラミックコンデンサー（MLCC）、塗料用体質顔料、光学ガラス等
世界的には石油やガス田の掘削用泥材への用途が圧倒的であるが、日本においては、本用途は少ない。MLCC.にはチタン酸バリウムが使用され、その原料として塩化バリウム、炭酸バリウム、水酸化バリウムが使用される。塗料用体質顔料には、重晶石の粉砕物と沈降性硫酸バリウムが使用される。光学ガラスには、炭酸バリウムや硝酸バリウムが使用される。その他の用途として、インキ、X 線造影剤、自動車ブレーキパッド、鉛蓄電池添加剤、樹脂安定剤、蛍光体、触媒等がある。
環境運命予測
Ingestion of toxic doses of barium affects the muscles, especially
the heart. Barium has a digitalis-type effect on the heart.
Ventricular fibrillation and slowed pulse rate are noted. This
may be related to barium’s tendency to displace potassium; the
resulting potassium deficiency causes muscle weakness.
輸送方法
UN1400 Barium, Hazard Class: 4.3; Labels:
4.3—Dangerous when wet material. UN1854 Barium alloys,
pyrophoric, Hazard Class: 4.2; Labels: 4.2—Spontaneously
combustible material. UN1564 Barium compound, n.o.s.,
Hazard Class: 6.1; Labels: 6.1—Poisonous materials.
純化方法
Barium is cleaned by washing with diethyl ether to remove adhering paraffin, then filed in an argon-filled glove box, washed first with ethanol containing 2% conc HCl, then with dry ethanol. It is dried in a vacuum and stored under argon [Addison et al. J Chem Soc 3868 1962]. It has also been purified by double distillation under 10mm of argon pressure.
Structure and conformation
The space lattice of Barium belongs to the cubic system, and its body-centered cubic lattice has a lattice constant of a=0.5009 nm.
不和合性
Barium powder may spontaneously
ignite on contact with air. It is a strong reducing agent and
Barium 337
reacts violently with oxidizers and acids. Reacts with water,
forming combustible hydrogen gas and barium hydroxide.
Reacts violently with halogenated hydrocarbon solvents,
causing a fire and explosion hazard.
廃棄物の処理
Barium in solution (see spill
handling) may be precipitated with soda ash and the sludge
may be landfilled.
バリウム 上流と下流の製品情報
原材料
準備製品