ヨウ素

種類

ヨードは、主に研究開発用試薬製品や、産業用化学薬品などとして販売されている物質です。

1. 研究開発用試薬製品

ヨードは、研究開発用試薬製品としては、主に医薬原料、試液調製原料、有機合成原料などに用いられます。容量の種類には、5g、25g、100g、500gなどがあり、実験室で取り扱いやすい容量での提供が中心です。昇華性があることから、通常冷蔵で輸送・保管されることの多い物質です。

2. 産業用化学薬品

産業用化学薬品としては、ヨードは20kgファイバードラムや50kgファイバードラムなどの荷姿で提供されている物質です。工場などで取り扱いやすい、大型容量での提供が中心となっています。

主に、レントゲン造影剤、殺菌防カビ剤、液晶関連などの一般工業や、医薬・保健薬・分析用試薬・有機化合物安定剤・飼料などの用途を中心として想定されている製品です。

解説

ヨウ素，周期表第17族に属し、ハロゲン元素の一つ。俗称ヨード。1811年フランスのクールトアが海藻灰の浸出液から各種の塩を除いた母液に過剰の硫酸を加えたところ、赤紫色の蒸気が発生した。これを冷却して暗紫色の結晶が得られたが、彼はこれを新しい元素であると考えた。

用途

これは下式のように、ヨウ化物イオンとの反応が起こることによる。

性質

ヨウ素，常温で金属光沢のある黒紫色の結晶。結晶はI2からなる分子格子で、熱すると紫色の蒸気となって昇華する。気体は二原子分子I2からなり、I-Iの結合の長さは2.667オングストローム（Å）。特異臭がある。化学的反応性は臭素よりさらに弱い。水素とは高温で、とくに白金触媒の存在下で反応する。水にはわずかしか溶けないが（100グラムに0.34グラム溶ける：25℃）、ヨウ化カリウムの水溶液によく溶ける（褐色）。たとえば100グラムの水に100グラムのヨウ化カリウムを溶かした水溶液には153グラムのヨウ素が溶ける。

存在と製法

ヨウ素，天然に遊離の状態では存在せず、海藻、海産動物中に有機化合物として含まれるほか、海水および地下鹹水(かんすい)中に微量含まれ、チリ硝石中にヨウ素酸塩（約0.05～0.3％）として含まれる。生体に必須(ひっす)の元素の一つである。たとえばヨウ化物イオンとしての存在量は、海生植物中30～1500ppm、陸生植物中0.42ppm、海生動物中1～150ppm、陸生動物中0.43ppm、哺乳(ほにゅう)動物の血液中0.063ppmである。海藻灰にヨウ化カリウムとして含まれるので、古くはこれに硫酸と二酸化マンガンを加えてつくった。日本では工業的に、ヨウ化物を多く含む地下鹹水（たとえば房総半島の地下鹹水中には80～130ppm含まれている）を塩素により酸化してからイオン交換樹脂に吸着させる、あるいは塩素を吹き込んで分子状ヨウ素とし、放散して析出させるブローイングアウト法などが行われている。また、チリでは、チリ硝石中に含まれるヨウ素酸ナトリウムNaIO3その他を、亜硫酸水素ナトリウムNaHSO3で還元してつくっている。

説明

Iodine, (I), is a nonmetallic element of family seven, the halogens. It is heavy, grayish-black in color, has a characteristic odor, and is readily sublimed to a violet vapor. It has a vapor density of 4.98, which is heavier than air. It melts at 236°F (113.5°C), has a boiling point of 363°F (184°C), and is insoluble in water. Iodine is toxic by ingestion and inhalation, and is a strong irritant to eyes and skin. The TLV ceiling is 0.1 ppm in air. Iodine is used for antiseptics, germicides, x-ray contrast material, food and feed additives, water treatment, and medicinal soaps. The four-digit UN identification number for iodine is only for the compounds iodine monochloride and iodine pentafluoride, and they are 1792 and 2495, respectively. The DOT lists iodine monochloride as a Class 8 corrosive, and iodine pentafluoride carries an oxidizer and poison label. Iodine does not have an NFPA 704 designation.

化学的特性

Heavy, grayish-black plates or granules having a metallic luster; characteristic odor. Readily sublimed having a violet vapor.Soluble in alcohol, carbon disulfide, chloroform, ether, carbon tetrachloride, glycerol, and alkaline iodide solutions; insoluble

物理的性質

Iodine in its pure state is a black solid that sublimates (changes from a solid to a gas withoutgoing through a liquid state) at room temperature. It produces a deep purple vapor that is irritatingto the eyes, nose, and throat. Iodine tends to form nonmetallic diatomic molecules (I₂).It is the heaviest of the naturally occurring halogens. (Although astatine, the fifth element ingroup 17, is heavier than iodine, it is a synthetic element and does not occur in nature exceptas a very small trace.) Iodine is the least reactive of the five halogens.
Iodine’s melting point is 113.7°C, its boiling point is 184.4°C, and its density is 4.93g/cm³.

同位体

There are a total of 145 isotopes of iodine. Only one (I-127) is stable andaccounts for 100% of iodine’s natural abundance on Earth. All the other 146 isotopesare radioactive with half-lives ranging from a 150 nanoseconds to 1.57×10⁺⁷

名前の由来

The name originates from the Greek word iodes, meaning “violet-colored,” which is the color of iodine’s vapor.

天然物の起源

Iodine is the 64th most abundant element on Earth. It occurs widely over the Earth, butnever in the elemental form and never in high concentrations.
It occurs in seawater where some species of seaweed and kelp accumulate the elementin their cells. It is also recovered from deep brine wells found in Chile, Indonesia, Japan,and Michigan, Arkansas, and Oklahoma in the United States. The iodine is recovered fromcremated ashes of seaweed. The ashes are leached with water to remove the unwanted salts.Finally, manganese dioxide (MnO₂) is added to oxidize the iodine ions (I^1-) to produceelemental diatomic iodine (I₂). The following reaction takes place: 4I^1- + MnO₂ → MnI₂ +I₂ + 2O^2-.
Chilean saltpeter [potassium nitrate (KNO₃)] has a number of impurities, includingsodium and calcium iodate. Iodine is separated from the impurities and, after being treatedchemically, finally produces diatomic iodine. Today, iodine is mostly recovered from sodiumiodate (NaIO₃) and sodium periodate (NaIO₄) obtained from Chile and Bolivia.

特性

Iodine is the least reactive of the elements in the halogen group 17. Most people associateiodine with the dark-brown color of the tincture of iodine used as an antiseptic for minor skinabrasions and cuts. A tincture is a 50% solution of iodine in alcohol. Although it is still used,iodine is no longer the antibiotic of choice for small skin wounds. Since iodine is a poisonthat kills bacteria, iodine tablets are often used by campers and others to purify water that istaken from outdoor streams.

来歴

Discovered by Courtois in 1811. Iodine, a halogen, occurs sparingly in the form of iodides in sea water from which it is assimilated by seaweeds, in Chilean saltpeter and nitrate-bearing earth, known as caliche in brines from old sea deposits, and in brackish waters from oil and salt wells. Ultrapure iodine can be obtained from the reaction of potassium iodide with copper sulfate. Several other methods of isolating the element are known. Iodine is a bluish-black, lustrous solid, volatilizing at ordinary temperatures into a blue-violet gas with an irritating odor; it forms compounds with many elements, but is less active than the other halogens, which displace it from iodides. Iodine exhibits some metallic-like properties. It dissolves readily in chloroform, carbon tetrachloride, or carbon disulfide to form beautiful purple solutions. It is only slightly soluble in water. Iodine compounds are important in organic chemistry and very useful in medicine. Forty-two isotopes and isomers are recognized. Only one stable isotope, ¹²⁷I, is found in nature. The artificial radioisotope ¹³¹I, with a half-life of 8 days, has been used in treating the thyroid gland. The most common compounds are the iodides of sodium and potassium (KI) and the iodates (KIO3). Lack of iodine is the cause of goiter. Iodides and thyroxin, which contains iodine, are used internally in medicine, and a solution of KI and iodine in alcohol is used for external wounds. Potassium iodide finds use in photography. The deep blue color with starch solution is characteristic of the free element. Care should be taken in handling and using iodine, as contact with the skin can cause lesions; iodine vapor is intensely irritating to the eyes and mucous membranes. Elemental iodine costs about 25 to 75￠/g depending on purity and quantity.

使用

Iodine is a halogen element extracted from chilean nitrate-bearing earth or from seaweed. it functions by its presence in the thyroid hormones. iodine deficiency is associated with goiter. sources are potassium and cuprous iodide and potassium and calcium iodate, of which the iodate form is preferred because of better stability. it is used as a food supplement.

定義

A dark-violet volatile solid element belonging to the halogens (group 17 of the periodic table). It occurs in seawater and is concentrated by various marine organisms in the form of iodides. Significant deposits also occur in the form of iodates. The element is conveniently prepared by the oxidation of iodides in acid solution (using MnO₂). Industrial methods similarly use oxidation of iodides or reduction of iodates to iodides by sulfur(IV) oxide (sulfur dioxide) followed by oxidation, depending on the source of the raw materials. Iodine and its compounds are used in chemical synthesis, photography, pharmaceuticals, and dyestuffs manufacture.
Iodine has the lowest electronegativity of the stable halogens and consequently is the least reactive. It combines only slowly with hydrogen to form hydroiodic acid, HI. Iodine also combines directly with many electropositive elements, but does so much more slowly than does bromine or chlorine. Because of the larger size of the iodine ion and the consequent low lattice energies, the iodides are generally more soluble than related bromides or chlorides. As with the other halides, iodides of Ag(I), Cu(I), Hg(I), and Pb(II) are insoluble unless complexing ions are present.
Iodine also forms a range of covalent iodides with the metalloids and non-metallic elements (this includes a vast range of organic iodides) but these are generally less thermodynamically stable and are more readily hydrolyzed than chlorine or bromine analogs.

危険性

less than pure form, it can damage the skin, eyes, and mucous membranes. Both the elementalform and its compounds (gases, liquids, or solids) are toxic if inhaled or ingested. Even indiluted form (e.g., a tincture of iodine to treat minor skin wounds), it should be used withcare.
Although a poison in high concentrations, iodine is required as a trace element in our dietsto prevent thyroid problems and mental retardation in the very young.

結晶の特性

ヨウ素の結晶は斜方晶系の構造を持ち、反磁性を示します。電気抵抗率 (0℃) は1.3×10⁷Ω⋅m、熱伝導率 (300K) は0.449 W/(m⋅K)です。酸化力は、フッ素、塩素、臭素のほかのハロゲン元素よりも小さいです。

使用用途

ヨードは、化学、医学を中心に幅広い分野において、多様な用途で使用されている物質です。主なものを下記に列挙します。

• 有機合成の中間体及び触媒、有機化合物安定剤、希有金属の製錬、分析用試薬
• 医薬品、保健薬、殺菌剤
• 診断治療、内科放射治療 (放射性ヨウ素131)
• 家畜飼料添加剤、染料、写真製版、農薬
• 薄層膜厚測定、送水管の欠陥検査、油田の検出

1. 分析化学

ヨウ素 (ヨード) の溶液は、デンプンを加えると、ヨウ素デンプン反応を起こして青紫色を呈する性質があります。この性質を活かしてヨウ素滴定 (ヨードメトリー) が行われたりします。

2. 医療分野

ヨウ素 (ヨード) は、消毒薬として広く用いられている物質です。代表的な消毒液には、ヨードチンキ (ヨウ素のアルコール溶液) や、ルゴール液 (ヨウ素とヨウ化カリウムのグリセリン溶液) 、ポビドンヨード (ヨウ素とポリビニルピロリドンの錯化合物) があります。

その他には、血管や各種臓器の診断に用いられるレントゲン造影剤の原料や、うがい薬があります。

3. その他産業分野

ヨードは、工業用触媒や農業分野でも使用されている物質です。防かび剤の原料等にも用いられます。さらに、最近では液晶パネルの偏光フィルム、太陽電池などのハイテク分野でも活用されています。

工業用途

Iodine is a purplish-black, crystalline, poisonouselementary solid, chemical symbol I, bestknown for its use as a strong antiseptic in medicine,but also used in many chemical compoundsand war gases. In tablet form it is usedfor sterilizing drinking water, and has less odorand taste than chlorine for this purpose. It isalso used in cattle feeds. Although poisonousin quantity, iodine is essential to proper cellgrowth in the human body, and is found in everycell in a normal body, with larger concentrationin the thyroid gland.
A wide range of compounds are made forelectronic and chemical uses. Iodine is also achemical reagent, used for reducing vanadiumpentoxide and zirconium oxide into highpuritymetals.

概要

ヨード (英: Iodine) とは、分子式I₂で表される二原子分子である単体のヨウ素の別名です。

元素としてのヨウ素は原子番号53のハロゲン原子であり、二原子分子を形成します。ヨウ素分子I2のCAS登録番号は、7553-56-2です。人間にとって必要不可欠なミネラルの1つであり、人間の体内では甲状腺に多く存在します。

また、甲状腺から分泌されるホルモンの主要な構成成分です。ヨードは海のミネラルとも呼ばれ、コンブやワカメなどの海藻や魚介類に多く含まれています。