176 



NATURE 



{Dec. 26, 1878 



coke ovens. Cur "perversity" in preferring hard to soft 

 coke is condemned, and we are invited to put reason in 

 the room of traditions which have not " one recorded 

 fact to sustain them.' ' 



My attention, as an iron-smelter, was drawn to the very 

 small consumption of charcoal in a certain instance quoted 

 by Prof. Tunner, of Leoben, and being unable to recon- 

 cile his experience with my own observations, I obtained 

 from this respected authority further confirmation of the 

 exactness of his figures. Along with this he kindly re- 

 peated his analyses, including one not given in his 

 original paper, viz., that of the gases taken on leaving the 

 furnace, in other words, after they had completed their 

 work. 



_ Other investigations prevented my examining the ques- 

 tion at the time with that attention it deserved, and I con- 

 cluded, upon other grounds than those advanced by Prof. 

 Church, that there was some actual difference in the 

 mode in which charcoal effected the reduction of at least 

 so7ne ores. 



In this I now think that I was mistaken, and I will 

 endeavour to prove that the author of the paper commits 

 a grave error in comparing two blast-furnaces working 

 upon different kinds and quantities of ores and flux used 

 in the production of pig-iron, I will also attempt to 

 demonstrate that the use of hard coke, held to with such 

 " singular perversity," can be maintained by "reason " as 

 well as by " tradition." 



Carbonic oxide, as is well understood, is the chief 

 reducing agent in the smelting of iron, and for our present 

 purpose we may regard it as the only substance which 

 deprives the metal, as it exists in ores, of its oxygen. The 

 carbonic acid which is formed by this deoxidising action 

 possesses a tendency, at certain temperatures, diametri- 

 cally opposed to that of the lower oxide of carbon — it 

 reoxidises the iron. 



This conflicting property of the carbonic acid is kept 

 in check, in iron smelting, by the presence of carbon in 

 the form of its lower oxide, being about double that 

 which is present in its highest form of oxidation. 



When I came to examine the ratio in which the carbon 

 in these two conditions existed in the escaping gases, as 

 described privately by Prof. Tunner, I observed that they 

 agreed very nearly with that which I imagine constitutes, 

 in furnaces using coke, a state of equilibrium between the 

 gases and the ore in the process of reduction. 



Now no one will dispute that when two pounds of 

 carbon are burnt to the state of carbonic oxide and one 

 pound to the form of carbonic acid the quantity of heat 

 is the same, from whatever source the carbon itself may 

 be derived. 



If, after having determined a perfect resemblance be- 

 tween the extent to which the fuel has been oxidized, in 

 the furnace, when using charcoal and using coke, we find 

 that there is no difference in the amount of heat wasted, 

 it is time to consider whether the pig-iron itself, obtained 

 by means of these two kinds of fuel, may not require very 

 different quantities of heat for its production. 



It may be here stated that the Cleveland furnaces in 

 England, with which I compared those of Carinthia, were 

 consuming 21 to 22 cwts. of coke against 14 or 15 cwts. 

 of charcoal used in the latter per ton of iron. The weight 

 of the slag produced in the former was very much the 

 larger of the two. The additional heat absorbed in 

 fusing this substance was further augmented by that re- 

 quired for the decomposition of silica and phosphoric 

 acid, the bases of which are found more largely in Cleve- 

 land than in Carinthian pig. The diminished quantity 

 of fuel burnt in the charcoal furnaces reduces very greatly 

 the weight of gases, and this consequently lessens the 

 amount of heat carried away through their instrumentality. 



The following figures exhibit the number of centigrade 

 heat units required, according to my calculations, per 

 unit of each kind of pig-iron referred to. 



Cleveland Carinthian 



Evaporation of water in fuel 



Reduction of oxide of iron and dissociation 



of carbonic oxide 



Expulsion of carbonic acid from carbonate 



of lime 



Decomposition of this carbonic acid 



,, water in blast 



,, silica and phosphoric acid 



Fusion of iron 



„ slag 



Loss by radiation 



Carried off in gases 



4460 2990 



Now when the proportions between the heat require- 

 ments and fuel-consumption come to be examined, we 

 find that the two sets of numbers agree almost exactly ; 

 for — 



4460 : 2990 : : 21 : i4"o8 



Since writing on this question, nearly seven years ago, I 

 have had frequent opportunities of examining the perform- 

 ance of charcoal-furnaces in Sweden, Italy, and Spain, as- 

 well as in Virginia, Kentucky, Ohio, Missouri, and Michi- 

 gan, in the United States. I soon became aware that dif- 

 ferent kinds of ores demanded very different quantities of 

 charcoal for their treatment. In some cases the weight wa& 

 nearly as low as that consumed in Carinthia, in others it 

 was quite as much as if coke had been the fuel employed. 

 I failed on every occasion to detect any circumstance 

 beyond the change in the ore itself, or in the nature of 

 the iron it afforded, to which I could ascribe the differ- 

 ence in question. All doubt, however, on the supposed 

 difference of value between the vegetable and mineral 

 fuel was dispelled on receiving from the owners of works 

 in the North of Spain and in Virginia, statements from 

 their books exhibiting the smelting of the same ores with 

 the two kinds of fuel. The difference in these was often 

 in favour of the coke, but such difference as existed could 

 easily be accounted for by fluctuations in the amount of 

 foreign matter in the fuel, or in small changes in the 

 quality of the ores. 



It only remains for me briefly to mention the grounds- 

 upon which, for chemical reasons, hard coke may be 

 superior to that softer variety recommended by Prof. 

 Church. 



Carbonic acid, as is pointed out in the paper by this 

 author, possesses the power of dissolving carbon, and 

 every pound so dissolved involves a double loss. There 

 is a reduction of temperature where the action takes 

 place, and there is a pound less of fuel remaining to be 

 burnt at the tuyeres. I ascertained, however, by direct 

 experiment, that all forms of carbon are not equally 

 easily affected by carbonic acid, that in hard coke being 

 capable of resisting the solvent action much better than- 

 the same carbon as it occurs in soft coke. The import- 

 ance, therefore, of employing our fuel in that condition 

 where it is least susceptible of being oxidized in the 

 region of the furnace where its combustion is useless, 

 need not be further insisted on. 



I am ready to admit with Prof. Church, that the tradi- 

 tional opinions of practical men have often required 

 correction from scientific investigation, but upon the 

 present occasion, so far as I have been able to judge, the 

 ironmaker and the chemist agree in the relative value of 

 hard and soft coke. I. Lowthian Bell 



PAP VAN HERPETOLOG V ^ 



IN this memoir, which forms a portion of the thirteenth 

 volume of the Anna/s of the Civic Museum of Genoa, 

 we have by far the best account of the herpetology of 



' " Catalogo dei Rettili"e'dei Batraci raccolti da O. Beccari, L. M. D'AI- 

 bertis e A. A. Bruijn, nella sotto-regione Austro-malese. " Por W. Peters 

 e G. Doria. Auu. del Mtis. Civko, Genova,.vol. xiii., 1878. 



