Most precious metals are available as sheet, tape, foil, wire, tubing, gauze, discs, electrodes, cathodes, crucibles, catalysts, and salts or solutions for plating and coating. Because pure gold is too soft for large, freestanding components, it is used chiefly for linings or electrodeposits and is often alloyed with other metals such as copper or nickel to increase strength or hardness. Gold is extremely inert. It is not attacked by nitric, hydrochloric, or sulfuric acid, but is dissolved by aqua regia and is attacked by sodium and potassium cyanide plus oxygen. Because it is not attacked by alkaline solutions, it is used to contain caustic soda and potash in all concentrations.
Silver has the highest thermal and electrical conductivity of all metals.
Alloyed with copper, and sometimes with zinc, silver is used in high-melting temperature solders. A silver-white metal, platinum is extremely malleable, ductile, and corrosion resistant. When heated to redness, it softens and is easily worked. It is nearly nonoxidizable and is soluble only in liquids that generate free chlorine such as aqua regia. Other applications include electrical contacts, resistance wire, thermocouples, and standard weights.