PRECIOUS METALS v 



ment, silver-plated amalgamated copper pl.-iti-s are not as 

 effective as the older type. Copper, iron and lead plates are 

 used in the order of their efficiency. Copper is more effective 

 than iron and iron is more effective than lead. The silver-plated 

 amalgamated copper plates are profitable only when a current 

 of low density is employed. 



Uses of Gold. Gold is used in the various arts and industries, 

 for coinage; for jewlery, spectacles, and pen making; in den- 

 tistry, and in chemical and photographic work. The beaten gold 

 1 :! I is used for gilded letters of signs, for lettering on book bind- 

 ings, for book edges, for mirror frames and picture frames, for 

 gilding metals. Gold dust is used in the moulding of furniture 

 or room decoration. The Japanese use gold largely in the manu- 

 facture of lacquers. Gold is drawn into wire and used for gold 

 lace, and other decorations. 



It may be of interest to know the relative proportion that 

 enters into these different fields: For coinage, 44 per cent.; for 

 jewlery, 24 per cent.; for exportation, 10 per cent.; watch cases, 

 10 per cent.; gold leaf, 2 1/2 per cent.; watch chains, 1 3/4 per 

 cent.; pens, dentistry and mechanical work, 1 1/4 per cent.; for 

 gold plate, 3/4 per cent. All these uses may be catalogued as its 

 use in American arts and industries. This will give for indust- 

 ries 40 per cent., coinage 44 per cent.; exportation 10 per cent. 

 These are based directly upon the coining value of the metal, or 

 $20.67 per Troy ounce. 



SILVER: ITS PROPERTIES, SOURCE AND USES 



Properties. Silver, symbol Ag, is known as the white metal. 

 It is pure white and susceptible of very high polish. When it is 

 in the form of a powder, it has a gray or earthy appearance. It 

 is malleable, ductile, and sectile, so that it can be rolled or ham- 

 mered into thin sheets and readily drawn out into extremely fine 

 wire. It is the best conductor of electricity known and its con- 

 ductivity is increased by the process of annealing. It is harder 

 than gold, and softer than copper. It is, therefore, alloyed with 

 copper in coinage. For United States coinage the standard is 

 nine parts of silver to one part of copper. Its specific gravity 

 is 10.50 when cast, and 10.57 when struck by the die in coinage. 

 Its melting point is 955 C., and its atomic weight is 107.88. 



Ores of the Metal. Silver occurs native containing small 

 quantities of gold, copper, iron, cobalt and antimony. It occurs 



