Although collectively known as the coinage metals, of the three group members only copper is still commonly used in the manufacture of coins. The British twenty pence coin, for example, is an alloy of copper and nickel, and the pound coin contains copper, nickel and zinc.
Copper, like silver and gold, is an excellent conductor of electricity, and so is widely used in electrical wiring. Its alloys, bronze and brass, are valued for their resistance to corrosion, and have various applications. Bronze is used in engine bearings and gear wheels, brass in ornaments and electrical plugs.
Both silver and gold are famously used in the manufacture of jewellery, but silver is also employed in electrical circuits and contacts, and its chloride, which darkens on exposure to air, is valuable in photography.
Gold, too, being resistant to corrosion and electrically conductive, is used in electrical components. It is also used in the settlement of international debts, and a gold compound is employed in the treatment of rheumatoid arthritis.
