REACTIONS IN BLAST FURNACES. 735 



No. 30. Reactions of phosphate of lead. Phosphate of lead forms, with chloride, bro- 

 mide, iiud iodide of lead, very volatile compounds (A. Guyard). This is proved by 

 the analysis of roasted cha-nber-dust and by that of the smoke caught in the Bartlett 

 filter. 



No. 31 Phosphate of lead is reduced by carbon and iron to the metallic state, like 

 oxide of lead (Percy Cloud). Part of the phosphoric acid found in the slags comes 

 from this reaction. 



No. 32. Reactions of chloride of lead. it is a well-known fact that chloride, bro- 

 mide, and iodide of lead are volatile compounds ; hence their constant presence in lead 

 fumes of every kind in Leadville. 



No. 33. Chloride of lead with lime and carbon. Chloride of lead is reduced to the 

 metallic state with formation of chloride of calcium and carbonic acid (Berthier): 

 2PbCl 2 +2CaO+C=Pb 2 +2CaC] 2 +CO 2 . The analyses of slags show that this reaction 

 does not take place in Leadville. It is chiefly due to the fact that chloride of lead is 

 volatilized before carbonate of lime is decomposed, and it indicates that there would be 

 an advantage in using caustic lime instead of raw limestone. 



N 34 Chloride of lead and galena. These two substances form a very volatile 

 chloro-sulphide of lead similar to galena (Berthier). This product has been found in 

 the portion of the lead fumes lost in the air. 



NO- 35- Reactions of metallic lead Lead is somewhat volatile (all authors). It has 

 been seen that normal accretions are chiefly formed of sublimated lead, and the con- 

 tents of this sublimated lead in silver were also given. 



REACTIONS OF SILVER COMPOUNDS. 



No. 36. Reactions of metallic silver Silver is somewhat volatile (all authors). The 

 assay of sublimated bullion found in normal shaft accretions gives an idea of the rel- 

 ative proportion of lead and silver volatilized and sublimated in the blast furnace. 



NO. 37. Reactions of sulphide of silver Sulphide of silver combines with metallic 

 silver and with sulphides of lead and iron. The analyses of bullion, skimmings, and 

 mattes show that these reactions take place in Leadville. 



No. 38 Sulphide of silver heated with oxide of lead is reduced to the metallic 

 state, with formation of an alloy of lead and silver and sulphurous acid : Ag 2 S+2PbO= 

 2(PbAg) + SO 2 (Percy-Smith). 1 



NO. 39 Sulphide of silver is not completely reduced to the metallic state by 

 metallic lead in excess (Percy). 



No. 40 Sulphide of silver is completely reduced to the metallic state by iron, 

 with formation of sulphide of iron (Berthier, Percy, and others). 



No. 41 Sulphide of silver is not completely reduced by iron in presence of an 

 excess of sulphide of iron (A. Guyard): The matte analyzed in XL, and which yielded 

 85.067 ounces of silver to the ton by scoriflcation, gave only 80.10 ounces when it was 

 treated directly with flux, litharge, an/l iron. This experiment throws light on many 

 furnace reactions. 



Reactions<of chloride of silver What is said for chloride of silver is true for bromide 

 and iodide. 



1 Quotations from Percy aud his assistants are taken from Percy's MetallHrgy of Silver aud 

 Gold. Part 1. London, 1880. 



