740 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



calated for 100 pounds of ore. This figure is calculated from the capacity of the 

 furnace, and represents very nearly a semi charge of smelter C, but as a great many 

 furnaces run charges of this weight it will be adopted in this discussion. The fur- 

 nace is capable of smelting this charge in about seven minutes, giving a cake of slag 

 weighing 281. G52 pounds, and it is assumed that at the time of the experiment the 

 furnace is properly filled with eleven similar charges, each charge being divided into 

 two layers, a layer of fuel and old slag and a layer of flux and ore, all these supposi- 

 tions and all the figures adopted being in perfect accordance with the practical work- 

 ing of the furnace. 



The composition in pounds of the charge in zone 150, the zone in which it is 

 thrown into the furnace, will be as follows : 



Carbon 79.r>;i9 



. Gases frooi fuel 2. 9.V> 



Carbonic acid (C 8. 747) 33.073 



Oxygen 33.7!i 



Moisture 22. 023 



Lead (total CO. combined with PbO = 14.667; PbO=6S.774; O=4.934) .. 63.840 



Silver. 0.930 



Metallic iron (FeaO^-Q.i.OSe ; FeO=86.620; Fe 2 O 3 =96.244) 07.371 



Oxide of lead in slag ;. 5.580 



A In in in. -i 12. OSM 



Peroxide of iron 2. .">!."> 



Peroxide of manganese (MnO- 9. 952; O=2.243) 12. 11).' 



Silica 78.606 



' \ (total CO in combinatiou=17.406) .. 

 Magnesia ) v \ 15. 717 



Alkalies 3. 153 



Old slag 52.3-23 



Total 502.527 



Weight of blast it will be seen in the discussion of losses in each zone of the 

 furnace that of the 79.599 pounds of carbon thrown in the furnace with each charge 

 only 32.1257 pounds reach the zone of combustion. It is this quantity of carbon which 

 will enable us to calculate the quantity of air necessary to convert it into carbonic 

 acid in seven minutes, an excess of air being injurious and calculated to cool the 

 furnace. As 32.1257 pounds of carbon require 85.C085 pounds of oxygen for their com- 

 bustion into carbonic acid, it is deduced from the composition of air given previously 

 that the air blown in the furnace in seven minutes will be composed of 



Oxygen 85. i 



Moisture 4.2023 



Carbonic acid 0. 1600 



Nitrogen 310.1031 



Total 400.1339 



In other words, the weight of air strictly necessary to burn the carbon left in the 

 smelting charge at the tuyeres is about four-fifths of the weight of the charge thrown 

 in at the feed-hole. At sea-level the volume of air corresponding to the weight of 

 400.1339 would be 5,356 cubic feet (1 cubic foot=538.569 grains). In Leadville, at the 

 normal pressure of 21 inches of mercury, the volume of the same weight of air is rep- 

 resented by 7,006.2 cubic feet. 



