Silver is the whitest metallic element. It is rare, strong, corrosion-resistant and unaffected by moisture, vegetable acids or alkalis. Silver is also resonant, moldable, malleable and possesses the highest thermal and electric conductivity of any substance. The chemical symbol for silver is Ag, from the Latin Argentum, which means white and shining. Although silver does not react to many chemicals, it does react with sulfur, which is always present in the air, even in trace amounts. The reaction causes silver to tarnish, therefore, it must be polished periodically to retain its luster.
Silver possesses many special physical characteristics and qualities that make it useful in a variety of industries. The photography industry is the biggest user of silver compounds. Silver forms the most light-sensitive salts or halides, which are essential to developing high-quality photography. Silver has the highest electrical conductivity per unit volume of any metal, including copper, so it is used extensively in electronics. Specialized uses include switch and relay contacts for automobile controls and accessories, automotive window heating and in electrodes for electrocardiograms.
Silver is one of the strongest oxidants, making it an essential catalyst for the chemical process industry. It is used in the production of adhesives, dinnerware, mylar recording tape and many other products. Silver is the most reflective of all metals and is used to coat glass in mirrors. It is also used in x-ray vacuum tubes and as material for bearings. With the highest level of thermal conductivity among metals and resistance to combustion and sparks, silver is a valuable material for a range of other industrial processes. The most common consumer application of silver is its use in jewellery. Pure silver, which would be too soft to be durable, is mixed with 5-20% copper in an alloy known as sterling silver.
Today, a very small percentage of the world’s silver is used in coinage, though silver coins were a popular form of currency until the recent past. As industrialized nations began to produce large numbers of silver coins in the twentieth century, silver became less available and therefore more expensive.
Silver was first obtained in sixteenth century Mexico by a method called the patio process. It involved mixing silver ore, salt, copper sulphide and water. The resultant silver chloride was then picked up by adding mercury. This inefficient method was superseded by the von Patera process. In this process, ore was heated with rock salt, producing silver chloride, which was leached out with sodium hyposulfite. Today, there are several processes used to extract silver from ores.
A method called the cyanide or heap leach process has gained acceptance within the mining industry because it is a low-cost way of processing lower-grade silver ores. However, the ores used in this method must have certain characteristics: the silver particles must be small; the silver must react with cyanide solutions; the silver ores must be relatively free of other mineral contaminants and/or foreign substances that might interfere with the cyanidation process and the silver must be free from sulfide minerals. The idea for cyanidation actually dates back to the eighteenth century when Spanish miners percolated acid solutions through large heaps of copper oxide ore. The process developed into its present form during the late nineteenth century. The cyanide process is described here.
How much silver will be produced in the future depends on many factors, including the rate of production of other metals and future uses of silver. Industrial demand for silver appears to be steady overall. Because silver naturally occurs with other metals, future production is linked to the production of copper, lead, gold and zinc.
In the future, silver will likely continue to be used for special industrial applications as well as for consumer items such as jewellery and silverware. In addition to these traditional uses, the value of silver will also depend on new uses for the metal. For example, using silver as a sanitizing agent is currently under development. Manufacturers have hustled in response to studies by the Atlanta-based Center for Disease Control that many viruses, including those linked to Acquired Immunodeficiency Syndrome (AIDS), will survive briefly outside an individual in fluids deposited on surfaces of plastic products such as telephones. Matsushita Electric Industrial Co. Ltd. in Osaka, Japan, completed a project at the Research Institute for Microbial Diseases, Osaka University, to produce a surface treatment that provides long-lasting sanitization for its plastic products. Research revealed the most effective system to be a compound based on silver thiosulfate.