REACTIONS IX BLAST FUEXACES. 745 



chlorobroiuo-ioilide of lead, wbicb is volatilized with the eblorophosphate of lead of 

 the ore, and reduced silver alloys with lead, formiug bulliou. Sulphide of silver is 

 partly acted upou by lead also, aud some galena is regenerated. Chloro-bromoiodide 

 of lead acts on galena aud volatilizes a portion of this substance. 



Zone 885° C. is one of the most important with regard to reactions. Silicate of 

 lead acts partly on the magnetic oxide of iron formed, reoxidizes it, aud some peroxide 

 of iron combines with silica. All the constituents of the charge are in a semi-fluid 

 condition, and all possible compounds are formed here, some of which will be destroyed 

 by thorough fusion in lower zones. Sulphate of lead is acted on energetically by 

 silica ; all the reactions of zone 780° C. are produced here also with even more energy. 

 Sulphide of carbon is formed and produces sulphides of silicium and magnesium. 

 Some volatile chlorides of nou volatile metals are also formed. All the reactions 

 which generate mattes are to be observed in this zone. In this zone also the quantities 

 of carbonic oxide and carbonic acid are nearly equal. Hematite loses completely the 

 carbouic acid of its carbonate of iron. Zinc, reduced in zones below, acts on galena, 

 and sulphide of zinc is formed. 



Zone 990° C. is one of very important reactions. Lime and magnesia being set 

 free act energetically on sulphide of lead and pyrites, forming the sul])hide of calcium 

 found in the slag. Silica combines with lime, magnesia, aud protoxide of iron, and 

 slag is formed. Oxide of lead is expelled fi'om its silicate. Phosphate of lead whici) 

 has escaped volatilization forms the phosphate of lime found in slags and accretions. 



lu zone 1,09.5° C, iron reduces arseniuret of lead, formiug si)iess, aud sulphide 

 of lead, formiug matte. It acts also on oxide of lead expelled from silicate, forming 

 magnetic oxide of iron, which enters the slag and the matte. This zone is the zone of 

 refining of bullion. It is here also that molybdic oxide is reduced and that iron and 

 speiss combine with it. 



The preceding chemical discussion was carried on also with a view to ascertain 

 the zones of absorption and of pioduction of heat in the furnace, and it was the writer's 

 intention to develop a complete thermic discussion of the different zones ; but neither 

 the time nor the means of determining with accuracy a few important data peculiar 

 to the blast-furnaces in which lead is smelted could be had, and a discussion based on 

 hypotheses would have lost all scientific or practical value. 



CONCLUSIONS. 



The chief conclusions arrived at in the preceding pages are: 



1. That smelting in Leadville is a profitable operation, but that the aggregate 

 smelting capacity of the working smelters is about equal to the present mining product 

 of the camp. 



li. That lead smelting in Leadville has, on the whole, been brought to a state of 

 great perfection with regard both to the plant adojjted, which is constructed on the 

 most approved principles, and to the manner in which fuel, fluxes, and ores are mixed 

 for smelting, giving slags which are remarkable for their fluidity and not too highly 

 charged with either silver or lead (especially when it is remarked that the bullion pro- 

 duced is very rich), aud from which by-products, such as speiss and matte, are easily 

 detached. 



3. That the quantity of by-products, other than lead fumes, resulting from smelt- 

 ing in Leadville amounts to but little. 



