Element gold has been called as the most beautiful because of its beauty which has made it desirable. Also, due its attractive color, brightness and for its art work. Gold is a dense, yellow, lustrous, precious metal which belongs to group 11(1b) and period 6 of the periodic table.
Gold is found in nature in comparatively pure form.Sources of Gold:In nature, gold is found as free metal and in tellurides. It is widely distributed metal and associated with pyrite or quartz. Gold is found in veins and in alluvial deposits. Depending on the location of the sample it occurs in sea water in the amount of 0.1 to 2 mg/ton.Uses of Gold:In coinage and as standard for many monetary systems.It is used for jewelry, dental work, plating, and reflectorsChlorauric acid is used in photography for toning silver images.
Physical characteristic properties of a Gold:Density (g/cc): 19.3Melting Point (°K): 1337.58Boiling Point (°K): 3080Appearance: soft, malleable, yellow metalDebye Temperature (°K): 170.00Pauling Negativity Number: 2.54First Ionizing Energy (kJ/mol): 889.3Oxidation States: 3, 1Lattice Structure: Face-Centered Cubic (FCC)Lattice Constant (Å): 4.080Specific Gravity (20°C): 18.88Atomic Radius (pm): 146Atomic Volume (cc/mol): 10.2Covalent Radius (pm): 134Ionic Radius: 85 (+3e) 137 (+1e)Specific Heat (@20°C J/g mol): 0.129Fusion Heat (kJ/mol): 12.68
Evaporation Heat (kJ/mol): ~340Chemical characteristic properties of a Gold:Gold is a yellow-colored metal it may be black, ruby, or purple in finely divided form.It is the most malleable and ductile metal.It is a good conductor of electricity and heat.Gold is not affected by exposure to air and to most reagents.Gold is an inert metal and a good reflector of infrared radiation.It is usually alloyed to increase its strength.The term karat is used to express the amount of gold present and pure gold is measured in troy weight, but only when gold is alloyed with other.
Extraction of Gold:Gold can be extracted by amalgamation or cyanidation which contains a variety of impurities, including zinc, copper, silver, and iron. There are two ways to remove gold from its ores. In the first method,Ore has to be mixed with mercury metal.Mercury is combined with gold in the ore to form an amalgam.Amalgam becomes a mixture of two or more metals in that one is mercury.Finally, the gold amalgam is removed from the ore and it is heated to drive off the mercury so pure gold is obtained.Refining:There are two methods for purification of gold.
Those are Miller process and the Wohlwill process. In the Miller process,All the impurities present in gold combines with gaseous chlorine more readily than gold does at temperatures equal to or greater than the melting point of the gold.Now impure gold is melted and gaseous chlorine is blown into the resulting liquidImpurities form chloride compounds that separate into a layer on the surface of the molten gold.Miller process is most rapid and simple, but it produces gold of only about 99.5 percent purity where as Wohlwill process increases purity to about 99.99 percent by electrolysis.