TRANSACTIONS OF SECTION B. 527 



Accordinpr to estimate it was believed that the reduction of oxide of iron ouphtto 

 he attended by an iuoreaso of temperature — in other words, tlie conversion of car- 

 bonic oxide into carbonic dioxide produced more heat than that absorbed by- 

 splitting up oxide of iron into its constituent parts. The estimated difference not 

 being a large one, an experiment was made by substituting in the furnace inert 

 substances having about the same specific heat as the ore. The results confirmed 

 the correctness of the calculation — the temperature of the escaping gases fell, and 

 rose to their normal point when the use of ore was recommenced. A more expen- 

 sive experiment wa.s subsequently made in the same direction by building, at Ferry- 

 hill, a pair of furnaces having a height of 103 feet, without any substantial benefit 

 being derived from the large additional expenditure incurred. 



It was Scheerer, I think, who first divided the blast furnace into zones. The 

 first division, beginning at the top and extending 12 feet downwards, was 

 designated the preheating zone; the following 18 feet downwards was dis- 

 tinguished as the reducing zone ; the next eight feet the carburising zone, followed 

 by four feet which constituted the zone of fusion. The lowest of all having a depth 

 of about six feet, was named the zone of combustion. The author of this mapping 

 out, as it were, of the interior of the furnace does not wish to be understood as 

 confining its various functions within the respective spaces assigned to them ; on 

 the contrary, he admits the existence of considerable variations of position. My 

 own observations, however, have led me to conclusions varying considerably from 

 those adopted by Scheerer. 



The fundamental cause of these differences seems to depend on the temperature 

 considered as being required for a commencement of the reduction of the ore. 

 By Scheerer the reducing zone is considered to require a temperature of 1,000° 

 to 1,200° C. This change undoubtedly is not the same with all kinds of 

 ores, but my experiments were conducted when using almost every variety of 

 the mineral. According to the trials made a mixture of one volume of carbon 

 dioxide and two volumes of carbonic oxide at a temperature of 410° removed 

 10 ^er cent, only of the oxygen in Cleveland ore, and 37-8 per cent, from an 

 artificially^ prepared oxide. The composition of the gases at the different depths, 

 however, indicates in an unmistakable manner the nature of the action which 

 is going on at any particular point. A table has been prepared from actual 

 analyses of the gases which gives the quantit}' of oxygen present for every 1,000 

 parts of metal produced; and to this is added the weight of carbon they 

 contained. The results vary, but the general inference to be drawn from the 

 observations made on furnaces of 80 feet is, that by the time the minerals have 

 passed through a space of eight feet of the depth they have to travel, all the oxygen 

 susceptible of removal from the ore in the upper region is found in the gases, the 

 remainder being retained until it reaches the zone of fusion. The same is the order 

 of action in a somewhat modified form which was found to prevail in the case of 

 furnaces 48 feet in height. 



On casting the eye along the lines of figures a somewhat remarkable circum- 

 stance is apparent, viz., that the quantity of oxygen per l,000of pig iron gradually 

 decreases as the gases ascend, until they approach the upper region, when it 

 commences to increase. This had been the subject of observation for many years 

 without any complete explanation being given of its cause. Dr. Percy, among 

 others, bestowed some attention to the circumstance without arriving at any 

 opinion satisfactory to himself. It is a little extraordinary that, so far as I have 

 seen, no notice has ever been taken of the fact that the carbon in the gases followed 

 the same law. While engaged in investigating the action of furnace gases on the 

 ore a peculiarity was observed previously unknown to me, viz., that large quantities 

 of carbon were deposited by the dissociation of the reducing gas, the action being 

 2 00 = COj + C. Experimentally I ascertained that spongy iron, as well as oxide 

 of iron, was capable of producing the change, and tbat 30 per cent, of carbon dioxide, 

 mixed with the carbonic oxide, arrested the reaction, the temperature at the time 

 being 420°. Dr. 0. A. Wright, who subsequently became chief chemist of our 

 laboratory, was asked to continue the examination. The conclusion arrived at was 

 the impossibility of effecting the complete reduction of Fe^Oj, or of any oxide, 



