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外観
銀白色の線状
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定義
本品は、電気分解処理により水中に銀を懸濁させたものである。
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溶解性
水に不溶。希硝酸や熱濃硫酸に可溶。他の酸に不溶。アルカリにより腐食される。熱硝酸に溶ける。
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解説
銀元素記号はAg。原子番号47，原子量107.8682。融点961.78℃，沸点2162℃。貴金属元素の一つ。古代から財宝，装飾品に用いられ，メソポタミアのウルク文化（前3400―前3100ころ），エジプトのゲルゼー文化（前3400―前3000ころ）の出土品に，銀製の装飾品が発見されている。日本では，《日本書紀》（674年）に対馬島貢銀の記載が文献上の産銀の初見である。加工性その他が良好なので，貨幣，装飾品，機械，器具などに用いられ，めっきの用途もひろい。電気や熱の伝導性にすぐれているので，電子部品や精密機器への用途が増えている。またハロゲン化銀は写真感光材料として重要。
株式会社平凡社 百科事典マイペディアについて 情報
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用途
元素分析におけるカラム充填剤。
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用途
高純度金属、合金材料、高純度銀化合物製造原料。
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主な性質
展性、延性は金に次いで大きく、厚さ0.0015ミリメートルの箔(はく)をつくれる。また1グラムの銀は1800メートルの線とすることができる。硬さ2.5～3。融解すると、空気中では多量の酸素を吸蔵し、凝固の際にこれを激しく放出する。熱、電気の伝導性は金属中最大（電気抵抗率1.59×10-6Ω・cm、熱伝導率0.998cal/cm・sec・deg〔20℃〕）。水および酸素に対して安定であるが、オゾンでは黒色の酸化銀AgOに、硫黄(いおう)や硫化水素で黒色の硫化銀Ag2Sになる。水素、窒素、二酸化炭素などとは高温でも反応しないが、ハロゲンには侵される。硝酸および熱硫酸に溶け、それぞれ硝酸銀、硫酸銀となる。アルカリには溶けないが、融解した水酸化ナトリウムには、空気の存在下で溶ける。通常の化合物での酸化数はⅠおよびⅡであり、Ⅲのものもある。
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存在
元素存在度は小さく、その量は少ない。天然には自然銀として産するほか、主として硫化物の形で産出する。主要鉱物は輝銀鉱、脆銀鉱(ぜいぎんこう)、硫アンチモン銀鉱、硫ヒ銀鉱などで、そのほか角銀鉱もある。また銅、鉛、亜鉛などの鉱石には多少含有されており、これらの金属を精製するとき、副産物としてかなりの量が得られている。世界で産額が多いのは、メキシコ、ペルー、オーストラリア、アメリカ、中国で、これらで世界総生産額の大部分を占めている。
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製法
含銀鉱石からの精錬には、金の場合と同じく、混汞法(こんこうほう)、シアン化法、乾式法などがあるが、混汞法はあまり用いられていない。
(1)シアン化法 自然銀、塩化銀、比較的純粋な硫化銀などが原料の場合に用いられる。一般に原料鉱石中に不純物が多く、採取率はそれほどよくはない（50～70％）。そのため、できるだけ細かく粉砕し、シアン化液の濃度を高め（0.3～0.5％）、十分攪拌(かくはん)して浸出時間を長くし、酸素を取り込んで収率をあげている（80～90％）。金に比べて精錬の費用がかかるので、独立した銀精錬が行われることは少なく、金とともに精錬している。
(2)乾式法 金の場合とまったく同じで、銅・鉛製錬の際、銅、鉛の鉱石に融剤として金鉱石のケイ酸塩を加えて製錬し、銅、鉛とともに取り出して最後に分離する。
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化粧品の成分用途
滑沢剤、抗菌剤、抗黴剤、皮膚コンディショニング剤、殺菌剤、消臭剤、着色剤
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主な用途
- 写真感光材料（フイルム、印画紙）
- 電気部品（コネクター等の接点、プリント基板、パソコン、ロボット、電装品、携帯電話）
- 銀ろう材（電気部品）
- 銀器装飾品（ナイフ、フォーク、水差し、ティーポット、装飾品）
- 歯科材（入れ歯）
- 日用品（魔法瓶）
- その他（触媒）
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説明
Silver is one of the earliest known metals. Silver has no known
physiologic or biologic function, though colloidal silver is
widely sold in health food stores. Silver has high thermal and
electrical conductivity and resists oxidation in air that is devoid
of hydrogen sulfide.
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化学的特性
Silver is a white lustrous metal that is extremely ductile and malleable. Silver does not oxidize in O2 by heating. It becomes Ag2O3 in O3 and black Ag2S3 in S2 and H2S. It is soluble in HNO3 and concentrated H2SO4 . It is not soluble in alkali.
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物理的性質
Silver is located in group 11 (IB) of period 5, between copper (Cu) above it in period 4 andgold (Au) below it in period 6. Thus, silver’s chemical and physical properties are somewhatsimilar to these two group 11 partners.Silver is a soft, while, lustrous metal that can be worked by pounding, drawing througha die, rolling, and so forth. It is only slightly harder than gold. It is insoluble in water, but it will dissolve in hot concentrated acids. Freshly exposed silver has a mirror-like shine thatslowly darkens as a thin coat of tarnish forms on its surface (from the small amount ofnatural hydrogen sulfide in the air to form silver sulfide, AgS). Of all the metals, silver isthe best conductor of heat and electricity. This property determines much of its commercialusefulness. Its melting point is 961.93°C, its boiling point is 2,212°C, and its density is10.50 g/cm3.
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同位体
There are 59 isotopes of silver, ranging from Ag-93 to Ag-130 with half-livesfrom a few milliseconds to a few days to 418 years. All but two of these 59 isotopes areradioactive and are produced synthetically. The two stable isotopes found in nature areAg-107 and Ag-109. These two make up 100% of the element’s existence in the Earth’scrust.
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名前の由来
Silver’s modern chemical symbol (Ag) is derived from its Latin word
argentum, which means silver. The word “silver” is from the Anglo-Saxon world “siolfor.”
Ancients who first refined and worked with silver used the symbol of a crescent moon to
represent the metal.
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天然物の起源
Silver is the 66th most abundant element on the Earth, which means it is found at about0.05 ppm in the Earth’s crust. Mining silver requires the movement of many tons of ore torecover small amounts of the metal. Nevertheless, silver is 10 times more abundant than gold.And though silver is sometimes found as a free metal in nature, mostly it is mixed with theores of other metals. When found pure, it is referred to as “native silver.” Silver’s major ores areargentite (silver sulfide, Ag2S) and horn silver (silver chloride, AgCl). However, most silver isrecovered as a by-product of the refining of copper, lead, gold, and zinc ores. Although silveris mined in many countries, including the United States, Mexico, and Canada, most silver isrecovered from the electrolytic processing of copper ores. Silver can also be recovered throughthe chemical treatment of a variety of ores.
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特性
Silver is somewhat rare and is considered a commercially precious metal with many uses.Pure silver is too soft and usually too expensive for many commercial uses, and thus it isalloyed with other metals, usually copper, making it not only stronger but also less expensive.The purity of silver is expressed in the term “fitness,” which describes the amount of silverin the item. Fitness is just a multiple of 10 times the silver content in an item. For instance,sterling silver should be 93% (or at least 92.5%) pure silver and 7% copper or some othermetal. The fitness rating for pure silver is 1000. Therefore, the rating for sterling silver is 930,and most sliver jewelry is rated at about 800. This is another way of saying that most silverjewelry is about 20% copper or other less valuable metal.
Many people are fooled when they buy Mexican or German silver jewelry, thinking theyare purchasing a semiprecious metal. These forms of “silver” jewelry go under many names,including Mexican silver, German silver, Afghan silver, Austrian silver, Brazilian silver, Nevadasilver, Sonara silver, Tyrol silver, Venetian silver, or just the name “silver” with quotes aroundit. None of these jewelry items, under these names or under any other names, contain anysilver. These metals are alloys of copper, nickel, and zinc.
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使用
This malleable white metal is found as argentite (Ag2S) and
horn silver (AgCl) or in lead and copper ore. Copper plates
coated with a thin layer of elemental silver and fumed with
iodine were used by Niépce and Daguerre. Aside from the
heliograph and physautotype, silver halide compounds were
the basis of all photographic processes used in the camera and
most of the printing processes during the 19th century.
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定義
A transition metal that occurs native and as the sulfide (Ag2S) and chloride (AgCl). It is extracted as a by-product in refining copper and lead ores. Silver darkens in air due to the formation of silver sulfide. It is used in coinage alloys, tableware, and jewelry. Silver compounds are used in photography. Symbol: Ag; m.p. 961.93°C; b.p. 2212°C; r.d. 10.5 (20°C); p.n. 47; r.a.m. 107.8682.
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一般的な説明
Silver is a noble metal, extensively used in SERS, photocatalysis and solar cells. The surface of silver can be functionalized to attain specific properties such as biocompatibility and vapor selectivity of sensors.3 Iodized silver foils and thin films find potential use as SERS-active metal substrates.1 Cu substrates laminated with Ag foils, have compatible coefficient of thermal expansion (CTE), to be used for electronic packaging. Porous ZnO nanoplates deposited on silver foil with tunable hydrophobicity may be fabricated.3
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反応プロフィール
Silver reacts violently with chlorine trifluoride (in the presence of carbon) [Mellor 2 Supp. 1 1956]. Bromoazide explodes on contact with Silver foil. Acetylene forms an insoluble acetylide with Silver [Von Schwartz 1918 p. 142 ]. When Silver is treated with nitric acid in the presence of ethyl alcohol, Silver fulminate, which can detonated may be formed. Ethyleneimine forms explosive compounds with Silver, hence Silver solder should not be used to fabricate equipment for handling ethyleneimine. Finely divided Silver and strong solutions of hydrogen peroxide may explode [Mellor 1:936 1946-47)]. Incompatible with oxalic acid and tartaric acid [Nav Aer. 09-01-505 1956]. Silver can form explosive salts with azidrine. ("Ethyleneimine" Brocure 125-521-65, Midland (Mich.), Dow Chemical Co., 1965). Ammonia forms explosive compounds with gold, mercury, or Silver. (Eggeman, Tim. "Ammonia" Kirk-Othmer Encyclopedia of Chemical Technology. John Wiley & Sons, Inc. 2001.). Acetylene and ammonia can form explosive Silver salts in contact with Ag. (Renner, Hermann, Gunther Schlamp. “Silver, Silver Compounds, and Silver Alloys." Ullmann's Encyclopedia of Industrial Chemistry. Wiley-VCH Verlag GmbH & Co. KGaA. 2001.)
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危険性
Toxic material.
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健康ハザード
The acute toxicity of silver metal is low. The acute toxicity of soluble silver
compounds depends on the counterion and must be evaluated case by case. For
example, silver nitrate is strongly corrosive and can cause burns and permanent
damage to the eyes and skin.
Chronic exposure to silver or silver salts can cause a local or generalized darkening
of the mucous membranes, skin, and eyes known as argyria. The other chronic
effects of silver compounds must be evaluated individually.
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火災危険
Dust is flammable.
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燃焼性と爆発性
Silver and most soluble silver compounds are not combustible. However, silver
nitrate and certain other silver compounds are oxidizers and can increase the
flammability of combustible materials.
Silver acetylide, azide, fulminate, oxalate mixtures, styphnate, tartarate mixtures,
and tetrazene are all explosives and must be handled as such.
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安全性プロファイル
Human systemic effects by inhalation: skin effects. Inhalation of dusts can cause argyrosis. Questionable carcinogen with experimental tumorigenic data. Flammable in the form of dust when exposed to flame or by chemical reaction with C2H2, NH3, bromoazide, ClF3 ethyleneimine, H2O2, oxalic acid, H2SO4, tartaric acid. Incompatible with acetylene, acetylene compounds, aziridine, bromine azide, 3-bromopropyne, carboxylic acids, copper + ethylene glycol, electrolytes + zinc, ethanol + nitric acid, ethylene oxide, ethyl hydroperoxide, ethyleneimine, iodoform, nitric acid, ozonides, peroxomonosulfuric acid, peroxyformic acid. See also POWDERED METALS and SILVER COMPOUNDS.
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職業ばく露
Silver may be alloyed with copper, aluminum, cadmium, lead, or antimony. The alloys are used in the manufacture of silverware, jewelry, coins, ornaments, plates, commutators, scientific instruments; automobile bearing; and grids in storage batteries. Silver is used in chromenickel steels, in solders and brazing alloys; in the application of metallic films on glass and ceramics, to increase corrosion resistance to sulfuric acid, in photographic films, plates and paper; as an electroplated undercoating for nickel and chrome; as a bactericide for sterilizing water; fruit juices; vinegar, etc.; in bus bars and windings in electrical plants; in dental amalgams; and as a chemical catalyst in the synthesis of aldehydes. Because of its resistance to acetic and other food acids, it is utilized in the manufacture of pipes, valves, vats, pasteurizing coils and nozzles for the milk, vinegar, cider, brewing, and acetate rayon silk industries.
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発がん性
The U.S. Department of Health
and Human Resources has extensively monitored published
studies on the occupational therapeutic and domestic exposures
to metals over many years, but has failed so far to
identify unequivocal clinical evidence that silver is carcinogenic
to humans under any circumstances. On the basis of
human experience and supportive studies in experimental
animals, silver is currently classified as a noncarcinogen
(62, 94, 141). On occasions patients exposed to silver in
antibiotic prostheses and other devices have died from
cancer, but in each case the role of silver in the etiology
of the malignancies was not proven.
It is expected that human contact with any of the radioactive
isotopes of silver may lead to local or other carcinogenic
changes in humans through the action of the radioactive
emissions as have been reported with gold in jewelry. No
cases have been seen to date.
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銀鏡反応
アンモニア性硝酸銀水溶液にアルデヒドなどの還元剤を加えて加熱すると，ガラスの器壁に銀が析出して鏡のようになる．これを銀鏡反応という．この反応ではアルデヒド RCHO によって，アンミン錯体中の銀が還元される．普通に使われている鏡は，この反応を利用して製造されているが，その際には還元剤としてグルコースが使われている．
銀鏡反応では，還元剤溶液と銀イオン溶液を混ぜた途端に反応が進行し，被めっき物表面だけでなく，溶液内で金属微粒子が同時に生成する．そのせいで，めっき浴は繰り返しては使えない．
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環境運命予測
Silver is a rare element, which occurs naturally in its pure form. It
is a white, lustrous, relatively soft, and very malleable metal.
Silver has an average abundance of about 0.1 ppm in the Earth’s
crust and about 0.3 ppm in soils. It exists in four oxidation states
(0,+1,+2,and +3). Silver occurs primarily as sulfides with iron,
lead, tellurides, and with gold. Silver is found in surface waters
as sulfide, bicarbonate, or sulfate salts, as part of complex ions
with chlorides and sulfates and adsorbed onto particulate
matter. Silver is released through natural processes, for example,
erosion of soils. Sources of atmospheric contamination arise
from processing of ores, steel refining, cement manufacture,
fossil fuel combustion, and municipal waste incineration. Of
anthropomorphic release, over 75% was estimated to be from
disposal of solid waste. Ore smelting and fossil fuel combustion
can emit fine particulates that may be transported long distances
and deposited with precipitation. The major source of release to
surface waters is effluent from photographic processing.
Releases from the photographic industry and from disposal of sewage sludge and refuse are the major sources of soil contamination
with silver. Silver can leach into groundwater, which can
be extenuated in acidic conditions. Silver can bioconcentrate in
fish and invertebrates.
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貯蔵
Most silver compounds should be protected from light during
storage or while in use.
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純化方法
For purification by electrolysis, see Craig et al. [J Res Nat Bur Stand 64A 381 1960]. For purification of crude, or silver residues to pure silver see Glemser & Sauer in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I pp 1028-1030 1963, and for the preparation of colloidal silver see ibid (Ed. Brauer) p 1034.
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不和合性
Dust may form explosive mixture with air. Powders are incompatible with strong oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explosions. Keep away from alkaline materials, strong bases, strong acids, oxoacids, epoxides May react and/or form dangerous or explosive compounds, with acetylene, ammonia, halogens, hydrogen peroxide; bromoazide, concentrated or strong acids, oxalic acid, tartaric acid, chlorine trifluoride, ethyleneimine.
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廃棄物の処理
Recovery, wherever possible, in view of economic value of silver. Techniques for silver recovery from photoprocessing and electroplating wastewaters have been developed and patented.
