cadmium

Cd. Atomic number 48. Electron configuration [Kr]4d ¹⁰ 5s ^2. Atomic weight 112.411(8). Eight stable isotopes with mass numbers 106 (1.25%), 108 (0.89%), 110 (12.49%), 111 (12.80%), 112 (24.13%), 113 (12.22%), 114 (28.73%), and 116 (7.49%) are known, as well as numerous radioactive isotopes ranging from 95 to 131. In the early 19th century, zinc oxide was used as a medicine, but Friedrich Stromeyer, a professor at the University of Göttingen who also served as a medicines inspector, analyzed samples brought in for testing purposes and confirmed that it was a new element. In 1817, he named it cadmium, after the Latin name for the zinc mineral calamine, cadmia. Cadmia comes from the Greek place name καδμεια [kadmeia]. In his book Shamitsu Kaisō, published in 1837, Udagawa Yoan transliterated this to Kadomitsu Umo (cadmium).
Abundance in the earth's crust is 0.098 ppm. Trace amounts are found in zinc minerals and coal. The largest reserves of cadmium are in China, the United States, Canada, and Kazakhstan, in that order, but in 2006 China (4,500 t), South Korea (2,800 t), and Japan (2,400 t) produced cadmium. The main raw material is zinc electrolyte slag from zinc smelting using sphalerite, which is treated with sulfuric acid to convert it into cadmium sulfate, which is then electrolytically extracted and distilled to refine it. A bluish silvery-white metal. Hexagonal crystal system. The structure is a hexagonal close-packed lattice. Density is 8.65 g cm ^-3 (25 °C). Melting point is 320.9 °C, boiling point 765 °C. Vapor density measurements show that it is a monoatomic molecule in gas form. It is highly malleable. Molar heat capacity at constant pressure is 26.04 JK ^-1 mol ^-1 (25 °C). Coefficient of linear expansion // c -axis 0.526× ¹⁰⁻⁴ K ⁻¹ . ⊥ c- axis 0.214× ¹⁰⁻⁴ K ⁻¹ (20 to 100 °C). Thermal conductivity 96.8 W m ⁻¹ K ⁻¹ (27 °C). Heat of fusion 6.11 kJ mol ⁻¹ (321 °C). Heat of vaporization 99.8 kJ mol ⁻¹ (767 °C). Electrical resistivity 6.83× ¹⁰⁻⁶ Ω cm (0 °C). Standard electrode potential (Cd2 ⁺ /Cd) -0.403 V. First ionization energy 867.6 kJ mol ⁻¹ (8.993 eV). Oxidation number 2. Easily forms amalgams with mercury. In air, it forms an oxide film on the surface, but the inside is not affected. When heated, it produces a red flame and brown smoke and becomes an oxide. It does not react directly with hydrogen, carbon, or nitrogen. It reacts with halogens at high temperatures. It dissolves easily in dilute nitric acid and slowly in hot hydrochloric acid.
It has excellent properties as a plating material to prevent corrosion of steel and other materials. It has many uses due to its unique physical and chemical properties, such as a low melting point and low coefficient of friction, but its use is decreasing due to environmental concerns. As a by-product of zinc smelting, cadmium production tends to increase when zinc production increases. Its main use worldwide was in nickel-cadmium batteries, but nickel-metal hydride batteries and lithium-ion batteries are gradually replacing it. It is also used as an alloy for low-melting-point solder, fuses, and bearings. It is also used in nuclear reactor control rods. Its use as a sulfide pigment is becoming increasingly restricted. According to the EU (European Union) Restriction of Hazardous Substances Directive, which came into force on July 1, 2006, electrical and electronic equipment sold within the EU is not permitted to contain cadmium, with some exceptions such as electrical contacts and cadmium plating. However, the Battery Directive, which requires batteries to be marked and collected, takes precedence. It is highly toxic and can cause kidney damage (renal tubular dysfunction). Itai-itai disease is a severe form of cadmium poisoning that occurs when high concentrations of cadmium are ingested for many years. The Food Sanitation Act stipulates that brown rice should not contain more than 1.0 ppm (1.0 mg of cadmium per kg of brown rice). As a specific Class 1 designated chemical substance under the PRTR Act, brown rice is designated as carcinogenic class 1 (carcinogenic to humans), oral class 2 (water quality standard value 0.01 mg L ^-1 or less), inhalation class 1 (air quality standard 0.001 mg m ^-3 or less), and work environment class 1 (gas 0.1 mg m ^-3 or less, particulate matter 0.01 mg m ^-3 or less). Furthermore, water quality laws and regulations stipulate strict standards such as an environmental standard for human health of 0.01 mg L ^-1 or less, a tap water quality standard of 0.01 mg L ^-1 or less, and a wastewater standard of 0.1 mg L ^-1 or less. [CAS 7440-43-9]

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

Cd．原子番号48の元素．電子配置[Kr]4d¹⁰5s²の周期表12族典型元素．原子量112.411(8)．質量数106(1.25％)，108(0.89％)，110(12.49％)，111(12.80％)，112(24.13％)，113(12.22％)，114(28.73％)，116(7.49％)の8種の安定同位体と，95～131に及ぶ多数の放射性同位体が知られている．19世紀初頭，酸化亜鉛鉱は薬剤として用いられていたが，医薬品検査官を兼ねていたゲッチンゲン大学教授のFriedrich Stromeyerが，検査目的でもち込まれた試料を分析して新元素として確認し，1817年に亜鉛鉱物calamineのラテン名cadmiaにちなんでcadmiumと命名した．cadmiaはギリシアの地名καδμεια[kadmeia]に由来する．宇田川榕菴は天保8年(1837年)に出版した「舎密開宗」で，これを音訳して嘉度密烏母(カドミウム)としている．
地殻中の存在度0.098 ppm．亜鉛鉱物，石炭中などに微量含まれる．カドミウムとしての埋蔵量は中国，アメリカ，カナダ，カザフスタンの順であるが，2006年の産出量は中国(4500 t)，韓国(2800 t)，日本(2400 t)となっている．主原料は，せん亜鉛鉱を原料とする亜鉛精錬の際の亜鉛電解液滓で，硫酸で処理して硫酸カドミウムに変換後，電解採取して蒸留で精製する．青味を帯びた銀白色の金属．六方晶系．構造は六方最密格子．密度8.65 g cm^－3(25 ℃)．融点320.9 ℃，沸点765 ℃．蒸気密度の測定から，気体では一原子分子．展延性に富む．定圧モル熱容量26.04 J K^－1 mol^－1(25 ℃)．線膨張率//c軸0.526×10^－4 K^－1．⊥c軸0.214×10^－4 K^－1(20～100 ℃)．熱伝導率96.8 W m^－1 K^－1(27 ℃)．融解熱6.11 kJ mol^－1(321 ℃)．蒸発熱99.8 kJ mol^－1(767 ℃)．電気抵抗率6.83×10^－6 Ω cm(0 ℃)．標準電極電位(Cd^2＋/Cd)－0.403 V．第一イオン化エネルギー867.6 kJ mol^－1(8.993 eV)．酸化数2．水銀とアマルガムをつくりやすい．空気中で表面に酸化皮膜を生じ内部は侵されない．加熱すると赤色の炎と褐色の煙を生じ酸化物となる．水素，炭素，窒素とは直接反応しない．ハロゲンとは高温で反応する．希硝酸とは容易に，熱塩酸には徐々に溶ける．
鉄鋼などの腐食を防ぐためのめっき材料として，すぐれた性質をもっている．低融点，摩擦係数の低さなど，特色ある物理化学的性質のため多方面の用途があるが，環境面の問題から使用量は減少しつつある．亜鉛製錬の副産物であるため，亜鉛の生産量が増加するとカドミウム生産量も増加する傾向にある．ニッケル-カドミウム電池用が世界的におもな用途であったが，ニッケル-水素電池，リチウムイオン電池に代替が進みつつある．合金として低融点はんだ，ヒューズ，ベアリング用にも使用されている．原子炉制御棒としても用いられる．硫化物の顔料としての使用は厳しく制限されつつある．EU(欧州連合)が2006年7月1日に施行した有害物質規制RoHS指令によれば，EU内で販売される電気電子機器には，カドミウムの含有は，電気接点，カドミウムめっきなど一部の例外を除いて許されない．ただし，電池にはマーク付けと回収を義務づける電池指令が優先される．毒性が強く，腎臓障害(尿細管機能異常)を起こす．イタイイタイ病は重いカドミウム中毒で，高濃度のカドミウムを長年にわたって摂取した場合に起こる．食品衛生法にもとづく規格基準として，「玄米は，カドミウムを1.0 ppm(1 kg の玄米中に1.0 mg のカドミウム量)以上含んではならない」と定められている．PRTR法・特定第一種指定化学物質として，発がんクラス1(ヒトに対する発がん性あり)，経口クラス2(水質基準値0.01 mg L^－1 以下)，吸入クラス1(大気基準0.001 mg m^－3 以下)，作業環境クラス1(気体0.1 mg m^－3 以下，粒子状物質0.01 mg m^－3 以下)の指定を受けている．さらに，水質関係法令では，人の健康にかかわる環境基準0.01 mg L^－1 以下，水道水質基準0.01 mg L^－1 以下，排水基準0.1 mg L^－1 以下などの厳しい基準が定められている．[CAS 7440-43-9]

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