Periodic Table and Technical information:
Symbol=Au
Atomic Number =79
Atomic Weight =196.9665 g/atom
Density (at 293 K) =19.32 g/cm3
Melting Point =1337.33 degrees Kelvin
Melting point =2,063 degrees Fahrenheit
Specific gravity is 19.32
Tensile strength =19,000psi
Hardness =2.75 on Mohs scale
Is one of the "Transition Metals" Boiling Point =2807.8 C (1337.59 K)
Modulus of Elasticity =79 G Pa
Brinell Hardness (annealed to 1031 K) =25 kgf/mm2
Reflectance at 0.40 um =38.7%
Reflectance at 0.55 um =81.6%
Reflectance at 0.70 um =96.7%
Reflectance at 1.00 um =98.1%
Thermal Expansion (from 273 to 373 K) =1.416 x 10^-7 K-1
Thermal Conductivity (at 273 K) =3.144 W/cm x K
Electrical resistivity (at 273 K) =2.05 x 10^-6 ohm x cm
Heat of Fusion =1.268 x 104 J/g-atom
Heat of Evaporation (at 298 K) =3.653 x 105 J/g-atom
Heat Capacity at 298 K =0.1288 J/g x K
Magnetic Moment =0.1439 N x m
Standard Oxidation Potential (Au to Au+ + e) =-1.68 V
Total Emissivity (from 493 to 893 K) =0.018 to 0.035
Properties of Gold:
Out of the earth comes a remarkable metal with an unparalleled combination of
chemical and physical properties that make this metal invaluable to a wide range
of everyday applications essential to our modern life. Thousands of common,
everyday appliances require gold to ensure perfect performance over a long
period of time. This indestructible metal is completely recyclable and virtually
immune to the effects of air, water, and oxygen. Gold will not tarnish, rust, or
corrode. This unique combination of properties makes gold a vital component in
many medical, industrial, and electrical applications.
Resistance to Corrosion:
Gold is the most non-reactive of all metals. It is benign in all natural and
industrial environments. Gold never reacts with oxygen (one of the most active
elements), which means it will not rust or tarnish. The gold death-mask in the
tomb of Tutankhamen looked as brilliant when it was unearthed in 1922 as when it
was entombed in 1352 BC.
Electrical Conductivity:
Gold is among the most electrically conductive of all metals. Since electricity
is essentially the flow of charged particles in a current, metals that are
conductive allow this current to flow unimpeded. Gold is able to convey even a
tiny electrical current in temperatures varying from -55° to +200° centigrade.
This makes gold a vital component for electrical connectors in computers and
telecommunications equipment.
Ductility and Malleability:
Gold is the most ductile of all metals, allowing it to be drawn out into tiny
wires or threads without breaking. As a result, a single ounce of gold can be
drawn into a wire five miles long. Gold's malleability is also unparalleled. It
can be shaped or extended into extraordinarily thin sheets. For example, one
ounce of gold can be hammered into a 100 square-foot sheet.
Infrared (Heat) Reflectivity:
Gold is the most reflective and least absorptive material of infrared (or heat)
energy. High purity gold reflects up to 99% of infrared rays. This makes gold
ideal for heat and radiation reflection, as in life-saving face shields for
astronauts and firefighters.
Thermal Conductivity:
Gold is also an excellent conductor of thermal energy or heat. Since many
electronic processes create heat, gold is necessary to transfer heat away from
delicate instruments. For example, a 35% gold alloy is used in the main engine
nozzle of the Space Shuttle, where temperatures can reach 3300° centigrade. Gold
alloy is the most tenacious and long-performing material available for
protection at these temperatures.
Gold Filled:
If an item is described as "gold filled", or "gold overlay", that means that a
layer of at least 10-karat gold permanently bonded by heat and pressure to one
or more surfaces of a support metal, then rolled or drawn to a prescribed
thickness. The karat gold must be at least 1/10 by weight of the total metal
content.
Rolled Gold Plate:
Material consisting of a layer of plating of 10-karat gold or better which is
mechanically bonded to a base metal. The karat gold content may be less than
1/20 but must be properly identified by weight in terms of total metal content.
Vermeil:
Gold at least 15- micro-inches thick, bonded to sterling silver by an
electrolytic or mechanical process.
Gold Leaf:
Pure gold that is pounded into sheets applied to other surfaces by hand. Usually
about 3 micro-inches thick.
Fools Gold:
Is not gold at all. It is a gold colored mineral found in other rocks like gold
often is. It is really iron pyrite and in relation to gold is worthless.
The Acid Test:
This is an expression that has entered popular language and means the final
proof, or undeniable. It comes from the need to be able to quickly and
positively determine not only if an item is truly gold or not, but also what
karat it is. One of gold's enduring qualities is that it does not tarnish or
oxidize easily. Nitric acid does affect gold and when applied in different
concentrations, can provide nearly infallible answers to questions of karat.
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