Important_amalgams Amalgam_(chemistry)

1 important amalgams

1.1 zinc amalgam
1.2 potassium amalgam
1.3 sodium amalgam
1.4 aluminium amalgam
1.5 tin amalgam
1.6 other amalgams
1.7 dental amalgam

important amalgams
zinc amalgam

zinc amalgam finds use in organic synthesis (e.g., clemmensen reduction). reducing agent in jones reductor, used in analytical chemistry.

potassium amalgam

for alkali metals, amalgamation exothermic, , distinct chemical forms can identified, such khg , khg2. khg gold-coloured compound melting point of 178 °c, , khg2 silver-coloured compound melting point of 278 °c. these amalgams sensitive air , water, can worked under dry nitrogen. hg-hg distance around 300 picometres, hg-k around 358 pm.

phases k5hg7 , khg11 known; rubidium, strontium , barium undecamercurides known , isostructural. sodium amalgam (nahg2) has different structure, mercury atoms forming hexagonal layers, , sodium atoms linear chain fits holes in hexagonal layers, potassium atom large structure work in khg2.

sodium amalgam

sodium amalgam produced byproduct of chloralkali process , used important reducing agent in organic , inorganic chemistry. water, decomposes concentrated sodium hydroxide solution, hydrogen , mercury, can return chloralkali process anew. if absolutely water-free alcohol used instead of water, alkoxide of sodium produced instead of alkali solution.

aluminium amalgam

aluminium can form amalgam through reaction mercury. aluminium amalgam may prepared either grinding aluminium pellets or wire in mercury, or allowing aluminium wire or foil react solution of mercuric chloride. amalgam used reagent reduce compounds, such reduction of imines amines. aluminium ultimate electron donor, , mercury serves mediate electron transfer. reaction , waste contain mercury, special safety precautions , disposal methods needed. environmentally friendlier alternative, hydrides or other reducing agents can used accomplish same synthetic result. environmentally friendly alternative alloy of aluminium , gallium renders aluminium more reactive preventing forming oxide layer.

tin amalgam

tin amalgam used in middle of 19th century reflective mirror coating.

other amalgams

a variety of amalgams known of interest in research context.

ammonium amalgam grey, soft, spongy mass discovered in 1808 humphry davy , jöns jakob berzelius. decomposes readily @ room temperature or in contact water or alcohol:






2
 

h

3


n

−

h
g

−

h
 


→

Δ
t



 
2
 
n

h

3


+

h

2


+
2
 
h
g



{\displaystyle \mathrm {2\ h_{3}n{-}hg{-}h\ {\xrightarrow {\delta t}}\ 2\ nh_{3}+h_{2}+2\ hg} }




thallium amalgam has freezing point of −58 °c, lower of pure mercury (−38.8 °c) has found use in low temperature thermometers.
gold amalgam: refined gold, when finely ground , brought contact mercury surfaces of both metals clean, amalgamates readily , form alloys ranging auhg2 au8hg.

dental amalgam


an amalgam dental filling

dentistry has used alloys of mercury metals such silver, copper, indium, tin , zinc. amalgam excellent , versatile restorative material , used in dentistry number of reasons. inexpensive , relatively easy use , manipulate during placement; remains soft short time can packed fill irregular volume, , forms hard compound. amalgam possesses greater longevity when compared other direct restorative materials, such composite. however, difference has decreased continual development of composite resins.

amalgam typically compared resin-based composites because many applications similar , many physical properties , costs comparable.