METALLURGY. 161 



This speiss contains an unusually small atomic proportion of arsenic, 

 for if the sulphur is supposed to be combined with the metals and arsenic 

 an arsenide of iron corresponding to the formula Fe 5 As 2 remains, whereas 

 in many speisses the arsenide of iron is either Fe 3 As 2 or Fe 4 As 2 . 



The analysis of slag shows that it is very basic and the formula deduced 

 from it is that of a subsilicate Although this slag is very much more basic 

 than is ordinarily the case where lead ores are profitably smelted, yet the 

 Eureka smelters claim that they obtain better results than they would if the 

 percentage of silica was much increased. The amount of arsenic in the 

 ore, which causes the formation of speiss, without doubt renders the smelt- 

 ing of such a basic mixture possible. The flue dust, which is collected in 

 long canals connected with a high stack on the hillside, is mixed to a thick 

 paste with clay and water in the proportion of one part clay and two parts 

 of dust, is somewhat dried, and added to the charge. 



Example of a charge. — The following is an example of a charge of one of the 

 furnaces: 



Charcoal scoops 40 



Kichinond ore shovels 50 



Kuby-Dunderburg (silicious ore) do 10 



Hoosac slag (silicious and rich) do 50 



Silver Lick (silicious ore) do 6 



Adobe flue dust do 4 



Speiss do 1 



Quartz ore do 2 



The Richmond ore contained three to four per cent, silica. The rest of 

 the silica required for smelting is supplied by the Ruby-Dunderburg, Silver 

 Lick, and other more or less quartzose ores, and by the Hoosac slag. The 

 Hoosac slag was a rich slag from the imperfect smelting of lead ore with a 

 quartz gangue. The charge is supposed to contain about the following per- 

 centages : 



Per cent. 



Ferric oxide 40 



Silica 20 



Plumbic oxide 22 



Other minerals 18 



100 



2654 L 11 



