テルル

外観

銀灰色の粒状

性質

にんにく臭がするテルル化合物が多いですが、テルル単体は無臭です。金属テルルの融点は449.51°C、沸点は988°Cであり、比重は6.232です。

化学的性質は、硫黄やセレンに似ています。空気中で青緑炎を上げて燃えて、二酸化テルル (TeO₂) が生じます。酸化力が強い酸に溶解し、ハロゲンと激しく反応してハロゲン化物を生成可能です。

テルルは弱酸性酸化物であり、酸化数は6、5、4、2、-2を取ります。

溶解性

[塩酸3 + 硝酸1(体積比)]に溶ける。

解説

Te．原子番号52の元素．電子配置[Kr]4d105s25p4の周期表16族非金属元素．原子量127.60(3)．質量数105～132の同位体が知られているが，120，122～126，128(31.74(8)％)，130(34.08(62)％)の8種が安定で，それ以外は放射性同位体である．1782年オTe．原子番号52の元素．電子配置[Kr]4d105s25p4の周期表16族非金属元素．原子量127.60(3)．質量数105～132の同位体が知られているが，120，122～126，128(31.74(8)％)，130(34.08(62)％)の8種が安定で，それ以外は放射性同位体である．地殻中の存在度0.01 ppm(深度20マイルまでの平均元素存在度)．カルコゲン中で存在量は最少で，硫化物中にテルル化物などとして存在する．銅，鉛などの電解精錬の副産物として得られる．六方晶系に属する銀白色のもろい半金属．融点449.5 ℃，沸点990 ℃．密度6.24 g cm－3(20 ℃)．酸化数－2，4，6．第一イオン化エネルギー9.009 eV．亜テルル酸(テルル(Ⅳ)酸H2TeO3)を二酸化硫黄で還元すると灰色の無定形テルルが得られる．水とは反応しないが，空気中で徐々に酸化され，熱すると青い炎をあげてTeO2になる．

主な性質

1. テルルは半金属であり、空気や酸素の存在下で燃える。
2. 水と塩酸には反応しないが、硝酸には反応する。
3. テルルは硫黄やセレンに類似している（より金属的で塩基性が高い）
4. 金属テルルを０．０１～１．０％添加すると快削性、強靭性、耐食性が改良される（快削鋼、特殊合金の添加剤として使用）

構造

金属テルルは銀白色の結晶で、六方晶構造を取っています。電子配置は、[Kr] 4d¹⁰ 5s² 5p⁴です。天然には、元素鉱物としてテルル単体やテルル金銀鉱物のほか、テルル銅鉱物やテルル鉛鉱物として、数多く存在します。

毒性

テルル単体やテルル化合物には、毒性があります。テルルは化合物を作って環境中に露出し、体内にも入りやすいです。体内でテルルは代謝され、生じたジメチルテルリド (英: dimethyltelluride) はニンニクに似た悪臭を持っています。

テルル化合物によって、鉱山労働者などに症状が多く報告されています。その場合には、暴露から遠ざけると改善可能です。具体的には、食欲不振、口渇、頭痛、悪心、傾眠、発汗停止、呼吸困難などの症状が報告されています。それ以外にも、体に青黒い斑点が現れ、発疹を生じるほか、口に金属味を感じます。

主な用途

1. 快削鋼の成分（自動車部品、精密機械部品）
2. 感光体（乾式複写機）
3. 化学工業添加剤
4. ターゲット材（光ディスクメモリ）
5. 熱電変換素子（金属間化合物、電子冷蔵庫、電子魔法瓶、赤外線センサ、太陽電池）

使用上の注意

不活性ガス封入

説明

Tellurium is one of the rarest elements on earth similar to selenium, and was discovered in Transylvania in 1782 by Franz-Joseph Muller von Reichenstein. The name derived from the Latin word for earth. Tellurium is occasionally found naturally, more often as telluride of gold, calaverite.

化学的特性

Tellurium is a grayish or silvery white, lustrous, crystalline, semimetallic element. It may exist in a hexagonal crystalline form or an amorphous powder.Soluble in sulfuric acid, nitric acid, potassium hydroxide, and potassium cyanide solutions; insoluble in water. Imparts garlic-like odor to breath, can be depilatory. It is a ptype semiconductor and its conductivity is sensitive to light exposure. It is found in sulfide ores and is produced as a by-product of copper or bismuth refining.

物理的性質

Tellurium is a silver-white, brittle crystal with a metallic luster and has semiconductorcharacteristics. It is a metalloid that shares properties with both metals and nonmetals, andit has some properties similar to selenium and sulfur, located just above it in group 16 of theperiodic table.
There are two allotropic forms of tellurium: (1) the crystalline form that has a silvery metallicappearance and a density of 6.24 g/cm³, a melting point of 499.51°C, and a boiling point of988°C; and (2) the amorphous allotrope that is brown in color and has a density of 6.015g/cm³and ranges for the melting and boiling point temperatures similar to the crystalline form.

同位体

There are a total of 48 isotopes of tellurium. Eight of these are consideredstable. Three of the stable ones are actually radioactive but have such long half-livesthat they still contribute to the natural abundance of tellurium in the crust of the Earth.The isotope Te-123 (half-life of 6×10⁺¹⁴ years) contributes 0.89% of the total telluriumfound on Earth, Te-128 (half-life of 7.7×10⁺²⁴ years) contributes 31.74% to the naturalabundance, and Te-130 (half-life of 0.79×10⁺²¹ years) contributes 34.08% to the telluriumin the Earth’s crust. The other five stable isotopes and the percentage of theirnatural abundance are as follows: Te-120 = 0.09%, Te-122 = 2.55%, Te-124 = 4.74%,Te-125 = 7.07%, and Te-126 = 18.84%. The other 40 isotopes are all radioactive withshort half-lives.

名前の由来

The name “tellurium” is derived from the Latin word for Earth, tellus.

天然物の起源

Tellurium is the 71st most abundant element on Earth. It makes up a small portion ofigneous rocks and is sometimes found as a free element, but is more often recovered fromseveral ores. Its major ores are sylvanite (AgAuTe₄), also known as graphic tellurium, calaverite,sylvanite, and krennerite, all with the same general formula (AuTe₂). Other minor ores arenagyagite, black tellurium, hessite, altaite, and coloradoite. In addition, it is recovered fromgold telluride (AuTe₂). Significant quantities are also recovered from the anode “slime” of theelectrolytic refining process of copper production.

特性

The pure form of tellurium burns with a blue flame and forms tellurium dioxide (TeO₂).It is brittle and is a poor conductor of electricity. It reacts with the halogens of group 17, butnot with many metals. When it reacts with gold, it forms gold telluride. Tellurium is insolublein water but readily reacts with nitric acid to produce tellurous acid. If inhaled, it produces agarlic-like odor on one’s breath.

使用

Tellurium is a common constituent of ores that contain silver, gold, lead, antimony, and bismuth, and it is often present in small amounts in coal. Tellurium is widely used in metallurgy because it improves the properties of copper, tin, lead-based alloys, steel, and cast iron. It is used in rubber manufacturing to increase heat resistance and to retard the aging of rubber hoses and cable coatings. Small amounts are used in the electronics industry for lasers and photoreceptors. Tellurium is not an essential micronutrient; therefore, it is not found in nutritional supplements.
As coloring agent in chinaware, porcelains, enamels, glass; reagent in producing black finish on silverware; in manufacture of special alloys of marked electrical resistance; in semiconductor research.

定義

tellurium: Symbol Te. A silvery metalloidelement belonging to group16 (formerly VIB) of the periodictable; a.n. 52; r.a.m. 127.60; r.d. 6.24(crystalline); m.p. 449.5°C; b.p.989.8°C. It occurs mainly as telluridesin ores of gold, silver, copper,and nickel and it is obtained as a byproductin copper refining. There areeight natural isotopes and nine radioactiveisotopes. The element is usedin semiconductors and smallamounts are added to certain steels.Tellurium is also added in smallquantities to lead. Its chemistry issimilar to that of sulphur. It was discoveredby Franz Müller (1740–1825)in 1782.

調製方法

Elemental tellurium (Te) has some metallic properties, although it is classed as a nonmetal or metalloid. The name is derived from the Latin word for earth, tellus. Tellurium is occasionally found naturally, more often as telluride of gold, calaverite. The elemental form has a bright luster, is brittle, readily powders, and burns slowly in air. Tellurium exists in two allotropic forms, in the form of powder and hexagonal crystalline (isomorphous) with gray selenium. The concentration in the earth’s crust is about 0.002 ppm. It is recovered from anode muds during the refining of blister copper. It is also found in various sulfide ores along with selenium and is produced as a by-product of metal refineries. The United States, Canada, Peru, and Japan are the largest producers.
Tellurium’s industrial applications include its use as a metallurgical additive to improve the characteristics of alloys of copper, steel, lead, and bronze. Increased ductility results from its use in steel and copper alloys. Addition of tellurium to cast iron is used for chill control, and it is a basic part of blasting caps. It is used in some chemical processes as a catalyst for synthetic fiber production, and as a vulcanizing agent and accelerator in the processing of rubber.

反応

塩酸，希硫酸に不溶，酸化力のある酸，王水，水酸化ナトリウム溶液に可溶．テルルは硫黄，セレンに似ているが，より金属的で塩基性も示す両性物質である．硫黄やセレンほど反応性は高くないが，濃アルカリ溶液でテルル化物と亜テルル酸塩となり，酸性にするとテルルが析出する．硫黄やセレンに相当する化合物が多いが，テルル酸H6TeO6は硫酸やセレン酸に比較して弱酸である．テルルは活性金属との反応により硫化物に似たテルル化物をつくるが，硫化物より不安定である．水素とは反応しないが，ハロゲンとは直接反応してハロゲン化物をつくる．陽性元素とは－2の酸化数の，陰性元素とは2，4，6の酸化数の化合物をつくる．また，Te42＋，Te62＋ などのポリ陽イオンもできる．

一般的な説明

Grayish-white, lustrous, brittle, crystalline solid; dark-gray to brown, amorphous powder with metallic characteristics. Used as a coloring agent in chinaware, porcelains, enamels, glass; producing black finish on silverware; semiconductor devices and research; manufacturing special alloys of marked electrical resistance. Improves mechanical properties of lead; powerful carbide stabilizer in cast iron, Tellurium vapor in "daylight" lamps, vulcanization of rubber. Blasting caps. Semiconductor research.

反応プロフィール

Tellurium is attacked by chlorine fluoride with incandescence. When Tellurium and potassium are warmed in an atmosphere of hydrogen, combination occurs with incandescence [Mellor 11:40. 1946-47]. Burning Tellurium produces toxic Tellurium oxide gas. Avoid solid sodium, halogens, interhalogens, metals, hexalithium disilicide. Reacts with nitric acid; reacts with concentrated sulfuric acid forming a red solution. Dissolves in potassium hydroxide in the presence of air with formation of deep red solution; combines with halogens. Avoid antimony and chlorine trifluoride; chlorine trifluoride reacts vigorously with Tellurium producing flame. Fluorine and Tellurium react with incandescence. Lithium silicide attacks Tellurium with incandescence. Reaction with zinc is accompanied by incandescence (same potential with cadmium, only hazard is less). A vigorous reaction results when liquid Tellurium is poured over solid sodium [EPA, 1998].

危険性

All forms of tellurium are toxic in gas form. The vapors of all the compounds of the dustand powder forms of the element should not be inhaled or ingested. When a person is poisonedwith tellurium, even in small amounts, the breath will smell like garlic.

健康ハザード

Although tellurium in elemental form haslow toxicity, ingestion can produce nausea,vomiting, tremors, convulsions, and centralnervous system depression. In addition,exposure to the metal or to its compoundscan generate garlic-like odor in breath, sweat,and urine. Such odor is imparted by dimethyltelluride that is formed in the body. Oralintake of large doses of the metal or itscompounds can be lethal. Clinical symptomsare similar for most tellurium salts,which include headache, drowsiness, lossof appetite, nausea, tremors, and convulsions.High exposure can produce metallictaste, dry throat, chill and other symptoms.Inhalation of dust or fume of the metalcan cause irritation of the respiratory tract.Chronic exposure can produce bronchitis andpneumonia.

火災危険

A finely divided suspension of elemental Tellurium in air will explode. Insoluble in water. Burning Tellurium produces toxic Tellurium oxide gas. Avoid solid sodium, halogens, interhalogens, metals, hexalithium disilicide. Reacts with nitric acid; reacts with concentrated sulfuric acid forming a red solution. Dissolves in potassium hydroxide in the presence of air with formation of deep red solution; combines with halogens. Avoid antimony and chlorine trifluoride; chlorine trifluoride reacts vigorously with Tellurium producing flame. Fluorine and Tellurium react with incandescence. Lithium silicide attacks Tellurium with incandescence. Reaction with zinc is accompanied by incandescence (same potential with cadmium, only hazard is less). A vigorous reaction results when liquid Tellurium is poured over solid sodium.

使用用途

金属テルルは、加工性や耐硫酸性の向上のために、耐酸性合金や鋼の合金添加剤に用いられます。テルル化合物は、特殊な着色剤 (や陶磁器の着色) 、酸化剤、熱電素子に使用可能です。

特に、電子冷凍装置の熱電対として多く使用されます。また、乾式コピー用感光ドラムに高純度の金属間化合物 (Se-Te) が使用されており、回収・再使用率も高いです。

さらに、金属テルルを鉄鋼に0.01～1.0％添加すると、快削性、強靭性、耐蝕性が改善されます。そのため、 (切削性に優れた鋼) は、自動車部品や精密機械部品などに使用されています。

産出

テルルの環境中の存在量は少ないです。ただし、単体の自然テルルとして、極まれに産出します。一般的にはテルル化物として硫化鉱中に少量混在し、金や銀のテルル化物としてわずかに存在します。

テルルの埋蔵量が多い国は、上位からアメリカ合衆国、ペルー、カナダの順です。年間生産量が多い国は、上位からカナダ、ベルギー、アメリカ合衆国、ペルー、日本であり、上位5ヶ国だけで生産量の82.3%に達します。

日本国内では、静岡県の河津鉱山や北海道の手稲鉱山で、マックアルパイン石や手稲石からテルル鉱物が得られます。工業的には、や鉛の電解精錬工場からのアノード泥が主原料です。ソーダ灰などと熱処理して可溶性のテルル酸塩とした後、中和して亜テルル酸 (TeO₂・nH₂O) として分離します。

同位体

テルルの同位体は、30種類知られています。天然に存在する¹²⁸Teや¹³⁰Teは放射性同位体であり、二重ベータ崩壊を起こします。¹²⁸Teの半減期は2.2×10²⁴年であり、知られている放射性同位体の中で最も長いです。

テルルはアルファ崩壊が起こる元素の中で、最も軽いです。¹¹⁰Teの0.003%がアルファ崩壊し、¹⁰⁶Snに変わり、それ以外は電子捕獲によって¹¹⁰Sbになります。質量数が109以下のテルルの同位体も、アルファ崩壊を起こします。

安定同位体の¹³⁰Teの中性子捕獲によって、人工放射性核種の¹³¹Teを生成可能です。¹³¹Iを人工的に得るときに使用されています。

安全性プロファイル

Poison by ingestion and intratracheal routes. An experimental teratogen. Exposure causes nausea, vomiting, tremors, convulsions, respiratory arrest, central nervous system depression, and garlic odor to breath. Aerosols of tellurium, tellurium dioxide, and hydrogen telluride cause irritation of the respiratory system and may lead to the development of bronchitis and pneumonia. Experimental reproductive effects. Under the proper conditions it undergoes hazardous reactions with halogens (e.g., chlorine, fluorine), interhalogens (e.g., bromine pentafluoride, chlorine fluoride, chlorine trifluoride), metals (e.g., cadmium, potassium, sodium, platinum, tin, zinc), hexalithium disilicide, silver bromate, silver iodate. When heated to decomposition it emits toxic fumes of Te. See also TELLURIUM COMPOUNDS.

職業ばく露

The primary use of tellurium is in the vulcanization of rubber and as an additive in ferritic steel production. It is also used as a carbide stabilizer in cast iron, a chemical catalyst; a coloring agent in glazes and glass; a thermocoupling material in refrigerating equipment; as an additive to selenium rectifiers; in alloys of lead, copper, steel, and tin for increased resistance to corrosion and stress, workability, machinability, and creep strength; and in certain culture media in bacteriology. Since tellurium is present in silver, copper, lead, and bismuth ores, exposure may occur during purification of these ores.

環境運命予測

Metals are recalcitrant to degradation; therefore, no biodegradation studies have been performed on tellurium. No aquatic bioaccumulation data exist for tellurium; however, based on its density and low water solubility, it is unlikely to present a concern for bioaccumulation in the water column. No environmental monitoring data are available on the levels of tellurium in sediment or sediment-dwelling organisms. Therefore, it is unclear whether tellurium has the potential to bioaccumulate in this compartment. In humans, tellurium accumulates in the bones. Based on this, it may be assumed that tellurium has the potential to bioaccumulate in vertebrates.

輸送方法

UN3288 Toxic solids, inorganic, n.o.s., Hazard Class: 6.1; Labels: 6.1-Poisonous materials, Technical Name Required.

純化方法

Purify it by zone refining and repeated sublimation to an impurity of less than 1 part in 108 (except for surface contamination by TeO2). [Machol & Westrum J Am Chem Soc 80 2950 1958.] Tellurium is volatile at 500o/0.2mm. It has also been purified by electrode deposition [Mathers & Turner Trans Amer Electrochem Soc 54 293 1928].

不和合性

Finely divided powder or dust may be flammable and explosive. Violent reaction with halogens, interhalogens, zinc and lithium silicide; with incandescence. Incompatible with oxidizers, cadmium; strong bases; chemically active metals; silver bromate; nitric acid.