Sept. 12, 1889] 



NATURE 



477 



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

 probable that a portion is due to the reduction of P2O5, S1O21 

 SO3, and CaO. In the case of Cleveland iron I have esti- 

 mated this at 54 parts per looo of pig-iron produced, but the 

 average total oxygen beyond that furnished by the blast in the 

 first two instances given was 130 parts. At this rate there 

 must have been 76 parts of oxygen liberated from the oxide of 

 iron, which is equal to 19 percent, of that originally combined 

 with the iron in the ore. 



It may be appropriate here to refer to what may be taken as a 

 typical expression of the working of a blast furnace in respect to 

 the presence of carbon dfoxide. An analysis of the gases is 

 therefore inserted, drawn from an 80-feet furnace at various 

 levels, with the simple remark that it is improbable that carbon 

 dioxide can exist for any length of time when exposed to incan- 

 descent 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 per- 

 mitted to burn vvastefully on the surface of the minerals charged 

 at the throat. This meant a loss of about 54 per cent, of the 

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

 of course impossible to utilize 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, however, consti- 

 tuted no reason why, apart from the furnace work itself, this vast 

 quantity of gaseous fuel should not have been utilized, as it no 

 doubt would earlier have been, had the ironmakers known, an 

 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 is 

 fully equal to four million tons of coal. 



In connection with the other volatile products which accom- 



Table IV. — Showing what may be regarded as a typical instance of the absence of Carbon Dioxide in the gases taken from a 

 furnace of 80 feet. Measurements taken from the highest level of the minerals, i.e. 8 feet below charging plates. 



pany the iron smelters' work I will only mention ammonia. 

 Some qualities 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-making, it is diluted in addition with all the fixed carbon 

 as oxides and all the nitrogen of the atmospheric air used 

 in its combustion. Nevertheless, Messrs. Bairds, of the Gart- 

 sherrie Works, and others, are manufacturing large quantities of 

 ammonia sulphate from the ammonia so obtainei. 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 com- 

 bustion of the gases evolved. These, before reaching the fire- 

 place where they are burnt, are deprived of their ammoniacal 

 vapours by passing through condensers provided for the pur- 

 pose. 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 

 that it seems improbable that this substance was not earlier 

 known to the ancients, as was at one time supposed. The 

 facility with which the metal combines with carbon renders it 

 very unlikely that acieration would not occasionally take place 

 •when iron itself was the object of the manufacturer. Certain 

 it is that Agricola, who wrote in 1556, describes in Latin a 

 mode, apparently as well known as that of making iron itself, 

 of making Acie. The engraving in his " De re metallica " 

 shows bars of malleable iron placed upright in a charcoal fire 

 resembling that of a Catalan hearth. These, after an exposure 

 of several hours to the incandescent charcoal and hot carbonic 

 oxide, were found changed to steel and employed as such. 



After the invention of the blast furnace, pig-iron was placed in 

 a similar hearth, and while in a melted state a blast of air was 

 directed upon the molten metal, until just as much carbon 

 remained with the iron as constituted steel. This mode of pro- 

 cedure continued to be practised long within my own recollection, 

 and may, for what I know, still be followed in some districts. 

 The subject of steel-making occupied the attention of Hassen- 

 fratz, of Reaumur, and others, but practically the only process 

 followed until 1865 was the well-known one of cementation. 



Since the days of Fourcroy it was ascertained that in addition 

 to the iron, carbon was an essential ingredient in cast metal, bu 

 invariably accompanied by more or less silicon, and wheneve 

 the minerals contained sulphur or phosphorus these metalloid 

 were also present. The nature of the actions employed fo 

 ridding the product of the blast furnace of these substances so a 

 to render it malleable had also been carefully examined and 

 explained by the light of scientific investigation. The manu- 

 facturer had, it is true, learnt by experience and observation how 

 to produce an article of excellence without much knowledge of 

 the science of his art. Among other things he ascertained 

 that to obtain a ton of wrought iron he required the heat 

 of an equal weight of coal in the puddling furnace ; but 

 he did not know, I'nor did even men of science, I think, ever 

 dream, that the oxidation of the metalloids in the pig-iron, and 

 that of a small portion of the metal itself, would afford heat 

 enough to enable the workmen to dispense with the use of all 

 coal in the process of conversion. When, therefore, the iron 

 trade was informed, in a paper read before the British Association 

 in 1856, entitled " A Mode of making Iron without the use of 

 Fuel," its author, Henry Bessemer, was set down by the iron trade 

 as a deluded enthusiast. At that period I doubt whether ten 

 pounds of wrought iron had ever been seen in a state of fusion at 

 one time. Bessemer, in his description, however, spoke of melting 

 tons of it with no more heat than that afforded by the rapid oxida- 

 tion of about 5 or 6 per cent, of the weight of the pig-iron used. 

 Not only, therefore, was the subject one of economic but also of 

 high scientific interest. Nevertheless, a mere statement of the title 

 of the paper was all the notice bestowed by our predecessors 

 in their Transactions on a discovery which has revolutionized 

 the art of making iron. It is quite true that for some time it 

 appeared as if the scientific aspect of the question were to constitute 

 its only recommendation, for the malleable iron made in a Bessemer 

 converter proved unmanageable when hot, and destitute of strength 

 when cold. Finally it was ascertained that phosphorus was the 

 source of the evil, and, further, that while carbon and silicon could 

 be almost entirely removed from the molten metal, this third 

 metalloid remained unaffected by the treatment. The extent to 

 which the hurtful influence of phosphorus makes itself felt in the 

 wrought iron obtained by the Bessemer process is somewhat 

 remarkable, because while two- to three-tenths per cent, is often 

 present in puddled bars of fair quality, probably no consumer 

 would accept Bessemer steel when it contains half of this 

 amount. The first success was obtained in Sweden, where by 

 using pig-iron containing a mere trace of the objectionable sub- 

 stance a product was obtained which was satisfactory. For 



