Gold uses. What are the uses of gold, gold coating, gold as a jewellery and more.
USES OF GOLD
Gold lends itself to the manufacture of decorative articles because of its great resistance to corrosion and tarnish and its ease of working. Impurities are added to the gold used for jewelry to impart the desired color to the metal and to harden it. In the past white gold was produced by the addition of palladium to gol d, but it is now manufactured from a gold-nickel alloy base. Gold alloys containing copper are red or pink in color and may be used for contrast in jewelry. The addition of silver to gold to form an 18 kt alloy gives a greenish color to the gold.
Purple of Cassius, also known as gold tin purple, is used in manufacturing red and purple glass and in colorirıg enamels and painting porcelain. The substance is a mixture of colloidal gold and tin oxide and is obtained from the reaction of gold chloride with stannous chloride.
Gold is used in electronics because of its good electrical conductivity and resistance to corrosion. Gold-nickel or gold-silver alloys are used in the manufacture of electrical contacts in relays and related equipment. if a hardener is required, platinum may be added. Gold is of ten used to coat the grids of electron tubes. Many gold-nickel or gold-iron alloys are magnetic and are used in computer memory devices.
Gold alloyed with palladium and copper is used in dental work, and gold alloyed with only palladium is used for the production of fusion resistant laboratory ware. The palladium raises the melting point of the laboratory vessels. Rhodium is of ten added as a hardener for the gold-palladium alloy.
Gold-backed mirrors are of ten used in spectroscopic equipment because of their superior reflecting qualities in the infrared region of the spectrum.
Gold compounds are used in the treatment of rheumatoid arthritis, as well as several other conditions. However, gold is quite toxic to some people, and its use must be carefully controlled.
The radioactive isotope 198Au is used for internal radiation therapy in the treatment of certain forms of cancer. This isotope has a half-life of 64.8 hours and may be used in metallic form, in colloidal form, and as gold thiosulfate. 198 Au is also used to detect lea.ks in filters fine enough to trap bacteria. The decay product of 198 Au is the stable mercury isotope 198Hg. The mercury thus produced may be collected and used in the production of mercury are lights.
Gold Coating of Materials:
Several methods may be used to cover obiects with a thin coat of gold, including electrodeposition, replacement plating, and organogold salt decomposition.
Replacement plating is essentially electro-plating without the application of an external current. Due to the ease of reducing gold from solution, an object made of nickel, for example, may release some nickel in contact with gold solutions by anodic dissolution with the resultant deposition of gold in its place.
Gold salts in solution may be decomposed by the addition of an organic reductant, such as oxalate or formaldehyde. The resultant precipitated metallic gold forms a thin coat on an immersed object, thereby forming the basis for electrodeless plating.
Organogold salts, when heated in all oxidizing atmosphere, decompose to yield metallic gold. This metallic gold can be plated on an object in coatings as thin as 7 millionths of an inch (17.8 x 10-6 cm).