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Later, Edward Frankland discovered that it could be synthesized by treating sodium amalgam with methyl halides: Hg + 2 Na + 2 CH 3 I → Hg(CH 3) 2 + 2 NaI. It can also be obtained by alkylation of mercuric chloride with methyllithium: HgCl 2 + 2 LiCH 3 → Hg(CH 3) 2 + 2 LiCl. The molecule adopts a linear structure with Hg–C bond lengths of ...
Amalgam filling on first molar. In dentistry, amalgam is an alloy of mercury used to fill teeth cavities. [1] It is made by mixing a combination of liquid mercury and particles of solid metals such as silver, copper or tin.
Zinc amalgam finds use in organic synthesis (e.g., for the Clemmensen reduction). [3] It is the reducing agent in the Jones reductor, used in analytical chemistry.Formerly the zinc plates of dry batteries were amalgamated with a small amount of mercury to prevent deterioration in storage.
Thus, amalgam (an alloy of mercury with another metal or metals, from the French word amalgame) was invented. This was further perfected in 1826, when Auguste Taveau of Paris used a silver paste made from mixing French silver-tin coins with mercury, which offered more plasticity and a quicker setting time. [3]
Sodium amalgam is a by-product of chlorine made by mercury cell electrolysis. In this cell, brine (concentrated sodium chloride solution) is electrolysed between a liquid mercury cathode and a titanium or graphite anode. Chlorine is formed at the anode, while sodium formed at the cathode dissolves into the mercury, making sodium amalgam.
Amalgam does not bond to tooth tissue and therefore requires mechanical retention in the form of undercuts, slots and grooves. However, if insufficient tooth tissue remains after cavity preparation to provide such retentive features, a cement can be utilised to help retain the amalgam in the cavity.
The periaqueductal gray (PAG), also known as the central gray, is a brain region that plays a critical role in autonomic function, motivated behavior and behavioural responses to threatening stimuli. [1] [2] PAG is also the primary control center for descending pain modulation. It has enkephalin-producing cells that suppress pain.
Composite resin and porcelain can be made to match the color of a patient's natural teeth and are thus used more frequently when aesthetics are a concern. Composite restorations are not as strong as dental amalgam and gold; some dentists consider the latter as the only advisable restoration for posterior areas where chewing forces are great. [142]