TBANSACTIONS OF SECTION B. 529 



by CO. On the contrary, when metallic iron known to contain no oxygen wfts 

 exposed to a current of f liis jras, carbon was deposited and oxygen absorbed. It would 

 seem, therefore, tliat this absorption of oxygen by the iron and precipitation of 

 carbon sutlice to explain tlie disappearance of these two elements from the gases, 

 and that they remain in this condition until the fusion of the iron, in contact 

 with intensely heated carbon, liberates the oxygen as well as that portion of the 

 carbon which is not absorbed by the metal in order to produce pig-iron. 



So far, then, as the analyses given in Table III. enable us to judge, instead of 

 the upper two-thirds of a furnace being required for the purposes of reduction, no 

 material change is effected after passing through 18 feet in a modem furnace 

 of 80 feet in height. After this the composition of the gases, and, therefore, of 

 the minerals, remains pretty steady until the vicinity of the tuyeres is reached, with 

 the consequences already referred to. 



Of the excess of oxygen at the zone of combustion it is highly probable that 

 A portion is due to the reduction of Pfi^, SiO.,, SO, and CaO. In the case of 

 'Cleveland iron I have estimated this at 54 parts per 1,000 of pig-iron produced, 

 hut the average total oxj-gen, beyond that furnished by the blast in the first two 

 instances given, was 130 parts. At this rate there must have been 70 parts 

 of oxygen liberated from the oxide of iron, which is equal to 19 per cent, of that 

 originally combined with the iron in the ore. 



It may be appropriate here to refer to what maybe taken as a typical expression 

 of the working of a blast furnace in respect to the presence of carbon dioxide. An 

 analysis of the gases is therefore inserted in Table IV., drawn from an 80-feet fur- 

 nace at various levels, with the simple remark that it is improbable that carbon 

 dioxide can exist for any length of time when exposed to incandescent coke at the 

 temperature which prevails at the depths mentioned in the last two columns. 



Something like forty years ago the escaping gases from the blast furnaces, rich 

 as they were in carbonic oxide, were permitted to burn wastefull}' on the surface 

 of the minerals cliarged at the throat. This meant a loss of about 64 per cent, of 

 the heating power of the coke. For reasons already given it was of course impos- 

 ■sible to utilise much of this heat in the actual smelting of the ore, because of the 

 necessity of preserving a large excess of carbonic oxide in the gases. This, how- 

 ■ever, constituted no reason whj', apart from the furnace work itself, this vast 

 quantity of gaseous fuel should not have been utilised, as it no doubt would 

 «arlier have been, had the ironmakers known, as they now do, its full value. To-day 

 all the blast and other engines are driven and the air is heated at our blast furnaces 

 by fuel formerly wasted, and this without any labour for stoking being required. 

 In Great Britain alone the annual saving from this course is fully equal to four 

 million tons of coal. 



In connection with the other volatile products which accompany the iron smelters' 

 work I will only mention ammonia. Some quaiities of coal admit of being used in 

 the raw state. In this case, as in distilling coal for illuminating purposes, ammonia 

 is generated and may be collected. Instead, however, of the ammoniacal vapour 

 being all contained in the hydrocarbons as in gas-makiog, it is diluted in addition 

 with most of the fixed carbon as oxides and all Ihe nitrogen of the atmospheric air 

 used in its combustion. Nevertheless, Messrs. Bairds, of the Gartsherrie works, 

 and others, are manufacturing large quantities of ammonia sulphate from the am- 

 monia so obtained. A similar object is achieved by attaching the necessary 

 condensers to the apparatus for coking coal. The process of distillation is then 

 carried on in hermetically closed ovens heated by the combustion of the gases 

 •evolved. These, before reaching the fire-place where they are burnt, are deprived 

 of their ammoniacal vapours by pas.sing through condensers provided for the 

 purpose. Previous, however, to this being done, the waste heat from the coking 

 process had been applied for generating steam, so that at certain collieries in the 

 county of Durham all the mechanical power is obtained without any coal being 

 specially burnt for this purpose. 



Before speaking of the next and last great improvements in connection with my 

 subject, I should like to say a few words, and a few words only, respecting steel, a 

 well-known and most valuable compound of iron and carbon. Let me first observe 



1889. M M 



