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SMELTING PROCESSES 



SMELTING PROCESSES AT FREIBERG. 



The Freiberg smelting processes have for their object the production of silver, lead, and copper (chiefly as blue 

 vitriol), from the ores obtained from the royal Saxon mines ; but, outside of these, from other purchased materials 

 and foreign ores (as for example, jewelers' sweepings and American ores), and middle products from previous smelt- 

 ing processes (silver, lead, etc.), but especially copper and gold from the foreign ores. The sulphur which is present 

 in the ores in great quantity is applied as much as possible to the manufacture of sulphuric acid, as also the greater 

 part of the arsenic present in the ores is converted into various products of the arts. White arsenic (arsonious acid), 

 red arsenic (realgar of commerce), yellow arsenic (orpiment of commerce), and black metallic arsenic (so called 

 cobaltum or Fly stone). They have also turned their attention lecently, with good result, to the experimental 

 production of zinc from the ores rich in that metal. The percentage of silver in the Freiberg ores comes especially 

 from more or less finely divided silver-glance, polybasite, stephanito, ruby silver ores, and silver Fahlcrz. Silver 

 occurs also occasionally though seldom, native, as a wiry, hair-like mass called washed silver, and in combination with 

 arsenic, tellurium and antimony. Lead occurs only as Galena in these ores ; copper as copper pyrites, peacock ore, 

 and copper ; Fahlerz and the other ores only as combinations with sulphur, never oxidized. The constituents of 

 these ores of secondary importance, which constitute the gangue, are iron pyrites, arsenical pyrites, zinc blende, and 

 earthy substances, such as quartz, lime, iluo spar, heavy spar, and brown spar. A. great part of the Freiberg ores 

 contain traces of gold, cobalt, and nickel, but not in paying quantity. 



Metallurgical Division of the Obbs, 

 All the ores are divided into 



1. Lead Ores. — Ores (without exception argentiferous) which make about one-third (£) of the entire production 

 of the mines. These are dividi d again according to their percentage of load, or the amount of their valueless con- 

 stituents, into 



a) Plumbiferous ores, and 



b) Glances (or galenoids). 



While the percentage of load in the former varies between fifteen and twenty-nine per cent., and the percentage 

 of the valueless constituents, such as iron pyrites, arsenical pyrites, zinc blende, and quartz, exceed it; in the latter it 

 goes from thirty per cent, to the highest percentage of lead possible, and flic gangue is only represented in small 

 quantity, 



Pure Galena (PbS) contains stoeohiometrically 86.61 per cent, lead ; but it never occurs in nature with so high a, 

 percentage of lead. The average percentage amounts to about 40 per cent, lead and 0.15 per cent. Ag. 



2. DiJBB Obes— These are the real silver ores, which contain no lead and copper (at least in paying quantity), 

 and frequently consist entirely of earthy gangue. As these so often contain arsenical pyrites, iron pyrites, and zinc 

 blende, they are divided according as one or the other of theso predominates. 



1st. Silicious, ] 

 2d. Spathic, I 

 3d. Pyritic, | 

 4th. Blendic, J 



Dttrr Ores. 



The silver in these varies from two-hundredths of a per cent. (0.02 p. c.) several per cent.; so that among them 

 occur the richest ores that arc brought to the furnace. 



3. CorPEK Ores. — These are also always argentiferous, but occur comparatively rarely. Their percentage of 

 copper varies between t per cent, and 10 per cent. ; is in the average, however, about il per cent. Their constituents 

 of secondary importance are mainly pyritic and blendic. Copper ores with a high percentage of copper are scarcely 



