Silver was known to ancient civilisations. Silver is a soft, malleable metal with a characteristic sheen. It has the highest thermal and electrical conductivities of all metals. It is generally found uncombined, or in the sulphide or arsenide ores from which it can be recovered as a cyanide complex which is subsequently reduced to the metal, in aqueous solution, by the use of zinc. The pure metal is stable to water and oxygen but is attacked in air by sulphur bearing compounds to form the characteristic black layer of silver sulphide. It is soluble in sulphuric and nitric acids. Some silver salts are sensitive to light (e.g. AgI, AgCl and AgBr) and are of fundamental importance to photography. Other applications and industries in which silver is used include the manufacture of jewellery (both as the pure metal and as a constituent of various alloys), the electrical industry (e.g. in the manufacture of contacts) and for the silvering of glass.Powder - Small particles with an approximately defined size range. Those materials described as alloy precursors are not true alloys - they are made by sintering a blend of powders of the component metals to achieve alloying by diffusion. The resultant cake is ground and sieved to the required particle size range. Unless otherwise stated, the particle sizes shown are for guidance only. We do not guarantee either any particular size distribution between the quoted minimum and maximum sizes, or a specific particle shape.