REACTIONS IN BLAST FURNACES. 737 



with those of iron smeltiug; but the following experiments, made by I. L. Bell in the 

 iron blast furnaces in the presence of the gases actually produced in smeltiug, show 

 with more accuracy the real process of the reduction of iron : 



(a) Furnace working with raw limestone; pieces of calcined Cleveland ore or 

 artificial hematite kept for two hours in the zone of the furnace below red point. 

 Composition of gases: CO=100 volumes; CO 2 =25 volumes; N=190 volumes. The 

 ore loses 11.85 per cent, of its oxygen (mean of two experiments). 



(b) Same experiment as in a, but in cherry-red zone. Composition of gases: 

 C 1=100 volumes; CO 2 =8J volumes; N=172 volumes. The ore loses 76.2 per cent, 

 of its oxygen, showing great reduction of iron. 



(c) Same experiment as in a and b, but in bright-red zone. Composition of gases : 

 CO^lOO volumes; CO 2 =3^ volumes; N=169i volumes. The ore loses 73.8 per cent, 

 of its oxygen. 



(d) Same experiment as preceding, but in very bright-red zone. Composition of 

 gases: CO=100 volumes; CO 2 =3 volumes; N=183J volumes. The ore loses 80 per 

 cent, of its oxygen. 



(e) Same experiment as preceding, but in intensely bright-red zone near tuyeres. 

 Composition of gases: CO=100 volumes; CO 2 =5 volumes; N=172 volumes. The 

 ore loses 71 per cent, of its oxygen. 



To interpret correctly these experiments we must take into consideration that 

 the ore does not remain exposed two hours to the influence of the gases of the same 

 zone in the furnaces of Leadville, and that although the reducing power of the cor- 

 responding zones is sensibly the same the quantity of ore reduced is greatly dimin- 

 ished. 



Reactions of sulphides of iron Pyrites existing in some ores and sulphide of iron 

 being formed in the furnace, the following reactions are interesting: 



No. 50. Protosnlphide of iron and peroxide of iron act upon each other with 

 formation of magnetic oxide of iron and sulphurous acid: FeS+10Fe 2 O 3 =7Fe 3 O 4 

 + SO 2 (Percy-Hochstatter). To this reaction is probably due in part the magnetic 

 oxide of mattes. 



No. 5'. Iron pyrites and oxide of lead react upon each other, give off sulphurous 

 acid, and form a magnetic mixture of sulphides and oxides of lead and iiou (Percy). 

 In this instance the origin of mattes is clearly indicated. 



CHEMICAL DISCUSSION OF THE LEADVILLE FURNACES. . 



The object of this discussion is to illustrate the chemical and metallurgical re- 

 actions of the blast furnace, and it is based as much as possible on general averages 

 obtained during the preparation of this report. 



It has already been seen (Table IV) : 



(1) That the average proportion of fuel to ore is 32.83 per cent. 



(2) That the average proportion of fuel to charge is 24.03 per cent. 



(3) That the average composition of the fuel used in the camp is: charcoal, 57 

 per cent.; coke 43 per cent. = 100 per cent. 



(4) That the average proportion of ash in coke is 22 per cent, and in charcoal 

 2.5 per cent., giving for the fuel under consideration an average of 10.88 per cent, of 



xn 47 



