974 



IRON 



The results obtained by M. Ebelmen from a coke-furnace at Seraing woro as 

 under : 



I. Gas obtained by plunging an iron tube, three centimeters in diameter, about 

 one foot into the furnace : II. the same ; the gas burnt spontaneously : III. and IV. 

 two consecutive analyses of the same gas : V. the gas was collected by an iron tube : 

 VI. gas collected by piercing the masonry two feet above the tuyeres ; the gas was 

 accompanied by fumes of cyanide of potassium, but no cyanogen could bo detached. 



The furnace was' 50 feet high; the air was supplied through two tuyeres, and was 

 heated to 212 ; it was driven at the rate of 26,840 gallons per minute under a pressure 

 of '6 of mercury. The charges were composed of, unroasted minerals 1,434 Ibs., 

 forge cinders 1,434 Ibs., limestone 948 Ibs., coke 1,765 Ibs. The metal was run 

 every twelve hours, and 17,500 Ibs. of white crystalline cast iron obtained, which was 

 run on thin plates and run directly to the puddling-furnace. The yield of the 

 mineral was 42 per cent, and the consumption of coke 1,500 per 1,000 of cast iron, 

 rising from 1,800 to 2,000 per 1,000 of iron when the furnace was working for foundry 

 iron. 



The analyses show a rapid diminution of carbonic acid, and indicate that in the 

 tipper regions of the furnace an energetic reduction of ore takes place by the oxide 

 of carbon under the influence of the high temperature of the ascending gases. 

 Between one and nine feet the limestone is calcined. The reduction of the ore takes 

 place at this region by the conversion of carbonic oxide into carbonic acid, without 

 change of volume and without consumption of carbon. The increase in the hydrogen 

 is too small to induce a supposition that aqueous vapour in decomposing can dissolve 

 any notable quantity of carbon. The gases collected at a depth of about 12 feet 

 represent about the mean composition of the gaseous mixture ; from that point to a 

 depth of 45 feet, two-thirds of the total height of the furnace, the gases do not 

 sensibly vary, and are combined almost entirely of carbonic oxide and nitrogen. At 

 12 feet the oxygen is to the nitrogen as 29'9 to 100 ; in atmospheric air it is as 26*3 

 to 100. The difference, 3'6, represents the oxygen arising from the reduction of the 

 silicates of iron constituting the forgo cinders, which is thus seen to take place 

 between the tuyere and a depth of 12 feet. These silicates are well known to be 

 decomposed with difficulty, but they are reduced at the high temperature prevailing 

 in that zone of the furnace, and their reduction gives rise to a corresponding quantity 

 of carbonic oxide, to a consumption of fuel, and to a considerable absorption of latent 

 heat. The other minerals are reduced higher up in the furnace, and this is common 

 to all coke -furnaces, being due to the high temperature of the ascending gases, a 

 temperature much higher than exists in charcoal -furnaces, a far larger quantify of 

 combustible being consumed. Henco it is that forge cinders can be successfully nurd 

 in coke-furnaces; while in charcoal-furnaces the introduction of small quantities 

 only alters the working of the furnace, makes the iron white, and corrodes rapidly 

 the walls of the furnace in consequence of the imperfect reduction. 



From his eudiometric experiments on the gases from coke- and charcoal-furnaces, 

 M. Ebelmen deduces the following conclusions : 



1. That the amount of carburetted hydrogen is too small to exercise any influence 

 over the chemical phenomena of the furnace. 



2. That the atmospheric air thrown into the furnace by the tuyere produces suc- 

 cessively carbonic acid and carbonic oxide, at a small distance from the opening. 

 Tho first of these reactions gives rise to an exceedingly hijzh temperature ; the seonid, 

 on the contrary, causes a great absorption of latent heat, and a corresponding lower- 

 ing of the temperature of the gaseous current. Tho limit of the zone of fusion bears 



