Amalgam
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- This article is about alloys. For the comic book series, see Amalgam Comics.
An amalgam is any alloy of mercury. Most metals are soluble in mercury, but some (such as iron) are not. Amalgams are commonly used in dental fillings.
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Dentistry
For some centuries dentists have been cleaning out decay and creating dental fillings, using filling material such as stone chips, resin, cork, turpentine, gum, lead and gold leaf. The renowned physician Ambroise Paré (1510 – 1590) used lead or cork to fill teeth. Amalgams were the first true standard filling material.
Mercury amalgams were used in dentistry because they were cheap, easy to use, durable, and regarded as safe. They are made by mixing approximately equal measures of mercury and an alloy of silver, copper, tin and other metals. There is an ongoing controversy because of the mercury content of amalgam.
The first people to use amalgam to fill cavities were the chinese in the 7th century.Template:Citation needed In 1816 Auguste Taveau developed a dental amalgam from silver coins and mercury. This early amalgam was low in mercury and had to be heated in order for the silver to dissolve at any appreciable rate. More modern dental amalgams are mixed cold. Current dental amalgams contain copper to eliminate the gamma-2 phase of the silver-mercury-tin alloy. The gamma 2 phase is weaker than the other phases so a high copper, low gamma-2 dental amalgam has superior strength.
Chemical analysis
Mercury is the preferred electrode material for the analysis of metals by anodic stripping voltammetry. The formation of amalgams facilitates the reduction of most metal ions in aqueous solutions that is normally not possible because their reduction potentials are more negative than the potential for the reduction of the solution.
Mining
Mercury amalgams have been used in the gold and silver mining process due to the ease with which mercury will amalgamate with them.
After all the usable metal had been extracted from the ore, mercury was poured down a long copper trough which formed a thin coating of mercury on the surface. The waste ore was then poured down the trough, and any gold in the waste amalgamated with the mercury. This coating was occasionally scraped off and distilled to remove the mercury, leaving behind fairly high purity gold.
The Spanish Empire transported mercury from Almaden across the Atlantic to supply the silver mines of Zacatecas and Potosí.
Other uses
Thallium amalgam is used as liquid for thermometers, because it freezes at -58°C, whereas pure mercury freezes at -38°C.
See also
Template:Wiktionaryzh-min-nan:A-má-káng da:Amalgam de:Amalgam eo:Amalgamo fa:ملغمه nl:Amalgaam ja:アマルガム no:Amalgam nn:Amalgam pl:Amalgamat pt:Amálgama ru:Амальгама sl:Amalgam fi:Amalgaami sv:Amalgam tr:Amalgam uk:Амальгама