An alloy is a mixture of two or more metals for a specific purpose. In the context of gold, the one addition to form an alloy will be gold. Other metals added to gold are copper, iron, aluminum, silver, platinum, palladium, nickel, zinc and titanium. The purpose of these alloys is to add color and strength. Gold in its purist form is very soft and can easily be deformed. For many applications gold needs to be alloyed for strength. This is true for the minting of coinage and jewelry. It is with gold alloys that the term karat comes in to play. The Kruger Rand for an example is 22 karat which means that it is 91.66% fine gold. The other metal used in the alloy combination is copper. The copper is used as a hardening agent for durability in resistance to scratches and other wear on the coin. In respect to gold jewelry it is often expressed in 8, 12, 16 and 18-karat fineness. The color and hardness of the jewelry will depend upon the other metal/metals used.
Often the term white gold is confused with platinum. White gold is exactly what the description says; “white gold”. White gold is a gold alloy where the other metal/metals used are zinc, nickel, platinum or palladium in part. The color of the alloy will appear white but in fineness it may be 12 karat gold. Adding copper yields a redder color, iron green, silver green, aluminum purple, platinum metals white, and natural bismuth together with silver produces black gold.
GOLD: VERY TECHNICAL
The following information is for those who seek “all knowledge”! For most of us this information is totally useless but in the spirit of completeness we go down to atom level, literally. Gold is a chemical element in the periodic table that has the symbol of Au (Latin for Aurum) Gold is a soft, shiny, yellow, dense, malleable, ductile (trivalent and univalent) transition metal. Gold does not react with most metals but is attacked by chlorine, fluorine and aqua regia (A yellow fuming corrosive mixture of nitric and hydrochloric acid that dissolves metals including gold). The metal occurs as nuggets or grains in rocks and in alluvial deposits. The ISO currency code for gold is XAU. The following information is the very technical regarding gold:
Name |
= |
Gold |
Gold Symbol |
= |
Au |
Atomic Number |
= |
79 |
Group |
= |
11 |
Period |
= |
6 |
Block |
= |
d |
Appearance |
= |
Metallic Yellow |
Atomic Mass |
= |
196.966569(4) g/mol |
Electron Configuration |
= |
[Xe]4f 14 5d 10 6s 1 |
Electrons per shell |
= |
2, 8, 18, 32, 18, 1 |
Phase |
= |
Solid |
Density (near r.t.) |
= |
19.3 g/cm? Elucidation: Compare the above with Aluminium: 2.7 g/cm?
Iron:7.87 g/cm? |
Liquid density at m.p
(melting point) |
= |
17.31 g/cm? |
Melting point |
= |
1337.33K, 1064.18°C, 1947.52°F |
Boiling point |
= |
3129K, 2856°C, 5173°F |
Heat of fusion |
= |
12.55 kJ/mol |
Heat capacity |
= |
(25 °C) 25.418 J/(mol·K) |
Crystal structure |
= |
cubic face centered |
Oxidation states |
= |
3,1 (amphoteric oxide) |
Electron negativity |
= |
2.54 (Pauling scale) |
Ionisation energies |
= |
1st: 890.1 kJ/mol |
Atomic radius |
= |
0.1442nm |
Electrical resistivity |
= |
0.022 micro-ohm m at 20 °C. |
Thermal conductivity |
= |
310 W m -1 K -1 at 20 °C. |
Hardness (Hv) |
= |
25 |
Tensile stress (MPa) |
= |
124 |
Number of naturally occurring isotopes |
= |
1 |
|
