Silver Ag

Discovery

Silver is one of the seven metals known in antiquity, alongside gold and copper. Around 5,000 years ago people in Anatolia and elsewhere were already extracting it from lead ores such as galena by cupellation, burning away the lead to leave silver behind.

Ancient Athens financed the fleet that fought Persia with silver from the mines at Laurion. In the sixteenth century Spain extracted immense quantities from Potosí, in today's Bolivia, and from Mexico, and silver crossed the Atlantic and Pacific to become the currency of world trade.

In the nineteenth century photography harnessed the way silver bromide and silver chloride darken in light, and film photography remained a major use of silver throughout the twentieth century.

Origin of the name

The English word silver comes from an old Germanic root. The symbol Ag comes from the Latin argentum, linked to an Indo-European root meaning "shining" or "white". The country Argentina takes its name from the same Latin word.

Main uses

• Solar cells: silver paste is printed to form the electrodes on silicon solar cells, a significant and growing share of demand.
• Electrical and electronic: its conductivity makes it ideal for switch contacts, conductive inks and brazing and soldering alloys.
• Jewellery, tableware and coins: sterling silver (92.5% silver) is the classic alloy, and bullion coins and bars are traded as investments.
• Mirrors and coatings: silver backs high-quality mirrors and forms heat-reflecting low-emissivity coatings on windows.
• Antimicrobial: silver ions disrupt bacterial enzymes and are used in wound dressings and water filters.
• Other: silver iodide is used to seed clouds.

Isotopes

Natural silver consists of two stable isotopes, silver-107 (about 51.8%) and silver-109 (about 48.2%). The radioactive isotope silver-110m, with a half-life of about 250 days, forms in reactor coolant and is monitored in radiation protection at nuclear plants. Silver readily absorbs neutrons, which is why silver–indium–cadmium alloy is used for reactor control rods.

In everyday life

Silver darkens over time because it reacts with traces of hydrogen sulfide in air, forming black silver sulfide. It tarnishes faster near boiled eggs or rubber bands. Tarnish can be removed with silver polish or with aluminium foil and baking soda.

Silver metal has low toxicity, but long-term ingestion of products such as colloidal silver can cause argyria, a permanent blue-grey discoloration of the skin. Claims that drinking silver preparations improves health are not supported by evidence.