816 



SILVER 



employed as to supplant, in many cases, the old processes of amalgamation and liqua- 

 tion previously described. The principal wet processes which have been largely used, 

 are those of Augustin, Ziervogel, and Von Patera. 



Augustin's Process. The argentiferous ore, or the matt or regulus, is first roasted 

 with common salt, whereby the silver passes into the state of chloride, which is then 

 dissolved out by a hot concentrated solution of salt ; chloride of silver being soluble in 

 hot brine. From this solution, the silver is precipitated by means of metallic copper. 

 This process was introduced at the Mansfeld Kupferschiefer works, in Prussian Saxony, 

 by Augustin, in 1849, but was abandoned in 1857. It was used at Freiberg, in 

 Saxony, between the years 1849 and 1862. 



ZiervogcVs Process. By roasting the argentiferous copper-matte, from the smelting 

 of the Kupferschiefer, in a reverberatory furnace, the iron is converted into sulphate, 

 which is then decomposed and yields peroxide of iron ; the copper also forms sulphate, 

 which is afterwards reduced to black oxide ; and in like manner, the silver present as 

 sulphide is oxidised to the state of sulphate. When, therefore, the roasted product is 

 lixiviated with hot water, the sulphate of silver is freely dissolved out, whilst the 

 oxides of copper and iron remain insoluble. The silver is precipitated in the metallic 

 form by means of copper. This is the process still employed at the Gottesbelohnungs- 

 hiitte Silver-extraction works, near Mansfeld. 



Von Patera's Process. This method is based on a suggestion made by Dr. Percy in 

 1848. The ore is first roasted with common salt, whereby chloride of silver is directly 

 formed, and this chloride is then dissolved out by a cold dilute solution of hyposul- 

 phite of soda. The silver is precipitated from this solution as sulphide, by addition 

 of sulphide of sodium ; and the silver sulphide is afterwards reduced to metallic silver 

 by heating in a muffle-furnace. This process was introduced by Von Patera at Joa- 

 chimstahl, in Bohemia, in 1858, and is believed to be still working. 



Sulphuric Acid Method. Argentiferous copper-matts are treated with hot dilute 

 sulphuric acid, whereby sulphate of copper is formed, and passes into solution, whilst 

 most of the silver and gold present is left in the residues. These are then smelted 

 with lead-ores, and the silver extracted from the argentiferous lead. This process is 

 now employed at Oker, in the Lower Hartz. 



Pattinson's process for extracting silver from argentiferous lead is fully described 

 under SILVER ; and Claudet's recent process for recovering silver from the liquors 

 obtained in the wet treatment of coppery pyrites, is duly noticed under PYBITES. 



The following statement of the production of silver in all parts of the world is 

 given by Mr. J. Arthur Phillips, chiefly on the authority of Duport and Chevalier. 

 See Phillips's ' Gold and Silver ' : 



Obtained from the island of Sardinia, where it is found associated with galena. 



