INTRODUCTION

Silver has been used since ancient times. It takes its name from the Latin word argentum, which means silver. Silver is a transition metal with electron configuration [Kr]4d105s1. It has a characteristic white color. It is a heavy metal with a density of 10.5 g/cm3. Its melting point is 961.8 °C, and boiling point is 2162 °C. It is the second metal after gold in malleabilty: a 2 km wire can be obtained from 1 g silver. Although it is the best conductor of heat and electricity of all the metals, silver cannot be used for that purpose because of its cost.

Silver is an inert metal so it is used in the jewellery industry. It is also used to plate of metal objects which are more active than silver to prevent their corrosion.

Occurrence

The percentage of silver in nature is very low 8 x 10~6%. Generally it is found in metallic form and as minerals in small amounts. The most important minerals are: argentite or silver glance (Ag2S), pyrangyrite or ruby silver (Ag3SbS3), silver - arsenic glance (Ag3AsSi3) and home silver (AgCl)

USES

Silver is widely used in the chemical industry despite not mixing easily with other substances. Powdered silver is an excellend catalyst used in industrial alcohol production and in production of fertilizers with ammonia compounds. Silver iodine compounds have been used to "seed" clouds, encouraging them to produce rain. This is not only useful in wiping out drought but also in taking the violence out of hurricanes before they reach populated areas. In the right conditions, 28 grams of silver iodine could produce 12 million liters of rain.

Silver is useful in medicine for absorbing the oxygen that germs need to live, there by killing them. Surgeons' instruments are often made from silver to reduce the chance of infection, and silver wire and plates can be used to repair broken limbs. Tooth fillings are made out of a silver, tin and mercury compound. Silver can also be used to purify water absorbing up to 20 times its own weight in water and killing the germs. This provides astronauts their supply of fresh water, and it can also be used by campers who get their water from streams and rivers.

Ag20 is used in mirror preparation, AgBr in photography, and AgN03 is used in medicines for eyes.

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