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性質
生理的にストロンチウムは、カルシウムに近い挙動を示し、骨格にも含まれています。ストロンチウムの融点は777°C、沸点は1,382°Cです。空気中で灰白色の酸化物被膜を生成します。水と激しく反応して、水素と水酸化ストロンチウムが生じます。
アルミニウムを用いて酸化ストロンチウムを還元すると、ストロンチウムを生成可能です。塩化ストロンチウムの溶融塩電解などによっても、金属単体が製造可能で、蒸留で精製できます。
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主な性質
- 単体ストロンチウムは銀白色の色調を持つ軽い金属である
- ストロンチウムは炎色反応で赤色を示す
- Ｓｒ９０はγ線を放出せず、β線のみ放出するので、β線厚み測定の標準物質に利用される
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解説
ストロンチウム，原子番号38の元素．電子配置1s22s22p63s23p63d104s24p65s2の周期表2族元素．原子量87.62．4種類の安定同位体(84Sr，86Sr，87Sr，88Sr)と14種類の放射性同位体の存在が知られている．銀白色の軟らかい金属．密度2.63 g cm－3(20 ℃)．面心立方格子構造．格子定数a ＝ 0.605 nm．融点770 ℃，沸点1384 ℃．炎色反応は紅赤色．化学的性質はカルシウムおよびバリウムに似てその中間の性質を示す．空気中では常温で表面が酸化皮膜で覆われる．高温で酸素，ハロゲン，炭素，ケイ素，窒素，硫黄と直接化合する．水素とは常温で水素化物をつくる．水銀とアマルガムをつくり，多くの金属と合金をつくる．酸に溶けてストロンチウム塩を生じる．水とはげしく反応して水素と水酸化ストロンチウムを生じる．特殊合金，真空管のゲッター，鋳物の品質改良に添加される．90Srは半減期28 y で核分裂生成物の一つである．β線源としてβ線厚み計に利用される．
森北出版「化学辞典（第2版）
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用途
ストロンチウム化合物は、少量が真空管、ブラウン管、永久磁石、特殊合金、花火などに使用されている。
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構造
ストロンチウムは、温度や圧力などの条件によって、3種類の結晶構造を取ります。常温常圧で安定な結晶構造は、面心立方格子構造 (α-Sr) です。213°C〜621°Cでは六方最密充填構造 (β-Sr) が、621°C〜769°Cでは体心立方格子 (γ-Sc) が最も安定しています。室温付近での密度は2.64g/cm3で、融点での液体密度は2.375g/cm3です。
ストロンチウムの電子配置は、[Kr] 5s2です。カルシウムと電子配置が似ているため、カルシウムの代わりに鉱物中へ入る場合もあります。
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製法
1790年A. Crawfordが鉱石中に炎色反応により見いだしたが，1808年H. Davy(デイビー)が電解によりはじめて単離した．Crawfordが炎色反応を観測した鉱石は，スコットランドのStrontian近くの鉛鉱山で見いだされたSrCO3鉱物で，strontianite(ストロンチアン石)と命名され，これをもとにDavyが元素名strontiumを1808年に提案した．重要な鉱石としては，天青石(セレスタイト)SrSO4，ストロンチアン石SrCO3などがある．地殻中の存在度260 ppm．酸化物のテルミット法によるか，塩化物の融解電解により得られる．蒸留により精製する．
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主な用途
- カラーTV（カラーテレビのブラウン管ガラス、パソコンのモニター）
- フェライト磁石材料（自動車用小型モーター、スピーカー、テープレコーダー）
- 花火（花火の火薬成分）
- 光学ガラス（カメラ、望遠鏡レンズ）
- 電着装置防錆剤（塗料の成分）
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説明
Strontium has the symbol Sr, the atomic number 38 and an atomic weight of 87.623 g/mol. As an alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. Due to its extreme reactivity with oxygen and water, this element occurs naturally only in compounds with other elements. The metal turns yellow when exposed to air. It occurs naturally in the minerals Celestine(SrSO4) and strontianite(SrCO3). The isotope, 90Sr, is present in radioactive fallout and has a half-life of 28.90 years. The following table presents the abundance of strontium. Strontium commonly occurs in nature, the 15th most abundant element on earth, averaging 0.034% in all igneous rock. It is found chiefly as the form of the sulfate mineral Celestite(SrSO4) and the carbonate Strontianite (SrCO3). Of the two, Celestite occurs much more frequently in sedimentary deposits of sufficient size to make the development of mining facilities attractive. Strontianite is more useful of the two common minerals because strontium is used most often in the carbonate form, but few deposits have been discovered that are suitable for development.
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化学的特性
Strontium is a silvery-white alkaline-earth metal that rapidly
assumes an oxide film and yellow color on exposure to air.
Strontium salts impart a brilliant red color to a flame. The
finely divided metal ignites spontaneously in air; therefore,
the metal should be stored under oxygen-free liquid.
Naturally occurring isotopes include 88Sr (82.56%), 86Sr
(9.86%), 87Sr, and 84Sr (0.56%). In addition, at
least 11 strontium isotopes are produced by fission; of these,
the 89Sr and 90Sr isotopes are considered to be environmentally
significant. 89Sr emits b-particles with an average
energy of 583 keV (1.46 MeV maximum) and has a halflife
of 50.5 days. 90Sr is a long-range b-emitter (mean
energy 195.8 keV; maximum 540 keV) with a half-life of
28 years. At least 20 strontium salts are known.
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物理的性質
In its elemental state, strontium is a relatively soft, pale yellow metal somewhat similar toelemental calcium. When freshly cut, strontium has a silvery shine to its surface that soonturns grayish as it is oxidized by atmospheric oxygen (2Sr + O2 → 2SrO) and nitrogen (3Sr +N2 → Sr3N2), which prevents further oxidation. Strontium’s melting point is 769°C, its boiling point is 1348°C, and its density is 2.54 g/cm3.
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同位体
There are 29 isotopes of strontium, ranging from Sr-75 to Sr-102. The fournatural forms of strontium are stable and not radioactive. These stable isotopes are Sr-84, which constitutes 0.56% of the element’s existence on Earth; Sr-86, which makesup 9.86%; Sr-87, which accounts for 7.00% of the total; and Sr-88, which makes up82.58% of strontium found on Earth. The remaining isotopes are radioactive with halflives ranging from a few microseconds to minutes, hours, days, or years. Most, but notall, are produced in nuclear reactors or nuclear explosions. Two important radioisotopesare Sr-89 and Sr-90.
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名前の由来
Strontium was named after the town Strontian, located in Scotland in
the British Isles.
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天然物の起源
Strontium metal is not found in its elemental state in nature. Its salts and oxide compoundsconstitute only 0.025% of the Earth’s crust. Strontium is found in Mexico and Spain in the mineral ores of strontianite (SrCO3) and celestite (SrSO4). As these ores are treated with hydrochloricacid (HCl), they produce strontium chloride (SrCl2) that is then used, along with potassiumchloride (KCl), to form a eutectic mixture to reduce the melting point of the SrCl2, as a moltenelectrolyte in a graphite dish-shaped electrolysis apparatus. This process produces Sr cations collected at the cathode, where they acquire electrons to form strontium metal. At the same time,Cl- anions give up electrons at the anode and are released as chlorine gas Cl2↑.Two other methods of producing strontium are by thermal reduction of strontium oxideand by the distillation of strontium in a vacuum.
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特性
When strontium metal is exposed to water, it releases hydrogen, as do the other earth metals (Sr + 2H2O → Sr(OH)2 + H2↑). Strontium can ignite when heated above its melting point.When in a fine powder form, it will burn spontaneously in air. It must be stored in an inertatmosphere or in naphtha. Several of its salts burn with a bright red flame, making it usefulin signal flares and fireworks.
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来歴
Both strontium and Strontianite are named after Strontian, a village in Scotland near which the mineral was first discovered in the ores taken from the lead mines. In 1787, an intriguing mineral came to Edinburgh from a Lead mine in a small village on the shores of Loch Sunart, Argyll, in the western highlands of Scotland. At that time, the substance was thought to be some sort of Barium compound. It was 3 years later that Scott s Irish chemist, Adair Crawford, published a paper claiming that the mineral held a new species including a new chemical element. Other chemists later prepared a number of compounds with the element, noting that it caused the candle s flame to burn red, while barium compounds gave a green color. The new mineral was named Strontite in 1793 by Thomas Hope, another professor of medicine at the University of Glasgow. This element was eventually isolated by Humphrey Davy in 1808 during his studies of the electrolysis of various alkaline earths containing molten chloride such as SrCl2 and mercuric oxide. He announced his work in a lecture to the Royal Society on 30 June 1808. In keeping with the naming of the other alkaline earths, he changed the name to Strontium.
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使用
This soft, yellowish, metallic element was isolated by Sir
Humphry Davy in 1808. It was found in the minerals strontianite
and celestine. The strontium halides were used in the
making of collodion emulsions.
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定義
Metallic element of atomic number
38, group IIA of periodic table, aw 87.62,
valence = 2, radioactive isotopes strontium-89 and
strontium-90. There are four stable isotopes.
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危険性
As a powder, strontium metal may spontaneously burst into flames. Both its metal andsome of its compounds will explode when heated. Some of the compounds will explode ifstruck with a hammer.
Both the metal and some compounds will react with water to produce strontium hydroxide[Sr(OH)2] and release hydrogen gas. The heat from the exothermic reaction may cause thehydrogen to either burn or explode [Sr + 2H2O → Sr(OH)2 + H2↑].
Some compounds, such as strontium chromate and strontium fluoride, are carcinogensand toxic if ingested. Strontium-90 is particularly dangerous because it is a radioactivebone-seeker that replaces the calcium in bone tissue. Radiation poisoning and death mayoccur in people exposed to excessive doses of Sr-90. Strontium-90, as well as some otherradioisotopes that are produced by explosions of nuclear weapons and then transportedatmospherically, may be inhaled by plants and animals many miles from the source of thedetonation. This and other factors led to the ban on atmospheric testing of nuclear andthermonuclear weapons.
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使用用途
ストロンチウムは、主に用添加剤として利用されています。かつては、ブラウン管のチューブガラスが主要用途でした。現在は、ディスプレイや太陽光発電用ガラスの添加剤（炭酸ストロンチウムとして）への利用が多いです。
その他、小型モーターなどの、、などにも使用可能です。さらに、硝酸塩の炎色反応が赤色を示すことから、花火の赤色光や発煙筒にも用いられます。
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産出
ストロンチウムは天青石 (SrSO4) として産出されます。主要な産出国は、中国、スペイン、メキシコです。小規模な産出国の具体例として、アルゼンチンやモロッコも挙げられます。アメリカにもストロンチウム鉱床が広く存在していますが、1959年以降には採掘されていません。
採掘された大部分の天青石は、炭酸塩に変えられます。炭酸ナトリウム溶液によって、直接天青石を抽出可能です。石炭で焙煎すると硫化物が得られ、硫化ストロンチウムを含有した暗色の物質が生じます。黒灰 (英: black ash) は、水に溶解するため、濾過で除去可能です。硫化ストロンチウム溶液に二酸化炭素を加えると、炭酸ストロンチウムが沈殿します。
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同位体
ストロンチウムの同位体の中で、84Sr、86Sr、87Sr、88Srの4種類が天然に存在します。存在率は、それぞれ0.56%、9.86%、7.0%、82.58%です。
87Srは、宇宙の元素合成のときに、84Sr、86Sr、88Srとともに生じた以外にも、天然放射性同位体である87Rbの崩壊によって生じます。87Rbの半減期は4.88×1010年です。87Sr/86Srの存在比は、地質学でよく報告されています。鉱物や岩石の87Sr/86Srは、0.7から4.0以上です。
ストロンチウムの不安定同位体は、16種類知られています。高エネルギーの電子を放つ同位体の中でも、とくに寿命が長いのは90Srであり、半減期は28.78年です。90Srはベータ崩壊によって、電子や反ニュートリノを放出して、90Yに変わります。
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発がん性
The carcinogenicity of stable
(nonradioactive) strontium chromate was attributed solely
to intracellular soluble chromium. 90Sr has been examined
in long-term studies in four species, involving beagles,
mice, monkeys, and pigs. A summary of the findings of these
studies can be found in Ref.. Following intravenous
injection of 90Sr at doses ranging from 0.027 to
362×104 Bq/kg, the most prominent 90Sr -induced endpoint
was bone sarcoma. Neoplasms involving the soft tissues near
bone in the oronasopharynx and paranasal sinuses and bone
marrow dysplasia were also significantly elevated over controls.
Feeding studies in beagles extending from the in utero
period to age 540 days resulted in the development of the
same array of tumors, and, in addition, myeloproliferative
disorders. Inhalation exposure to 90Sr Cl2 was associated with multiple carcinogenic and non-neoplastic lesions in
dogs, with an excess of bone tumors reported as the major
finding. Interestingly, inhalation exposure of dogs to insoluble
forms of 90Sr was associated with lung tumors, but not bone
tumors. In an additional study in which beagle dogs were
injected with lowlevels of 90Sr (21.1 kBq/kg, or five times the
maximum permissible (retained) body burden), 90Sr was not
associated with a decrease in survival time in dogs. It has
been estimated that 90Sr is approximately two orders of
magnitude less toxic than radium. Two monkey studies
were also summarized by the Council on Radiation Protection
and Measurements. One of these studies involved
administration of single intravenous injections of 90Sr
(0.10–6.21 MBq) to rhesus monkeys. These monkeys had
no symptoms or disease attributable to 90Sr 20 years after
exposure. In another study, administration of 1.85 or 3.7 MBq
of 90Sr as a single oral dose resulted in bone sarcomas.
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環境運命予測
Most stable strontium and some radioactive strontium
compounds exist as dust in air, which eventually settles over
land and water. Stable strontium dissolves in water and moves
deeper in soil to underground water. The solid is found suspended
in water. Strontium is also found naturally in soil due
to the release of coal ash and industrial wastes. Soluble strontium
compounds, through chemical reactions, can transform to
insoluble and vice versa. The long half-life of strontium-90 (29
years) can allow airborne particles to move all around the
world.
