588 KEPOET— 1891. 



last observation leads us insensibly,' he adds, ' to Tery important reflections on the 

 use of carbon in the reduction of metals.' It most certainly did, and by 1815 an 

 accurate, if incomplete, view of reduction had passed into the encyclopaedias. It 

 was seen that the removal of oxygen from burnt metals, by carbon, ' give the 

 metals,' as Fourcroy and Vauquelin put it, ' a new existence.' Some ten years 

 later Le Play attempted to show that reduction is always effected by the inter- 

 vention of carbonic oxide, which elicited the classical rejoinder from Gay-Lussac, 

 who pointed out that ' carbon alone, and at very moderate temperatures, will- 

 reduce certain metallic oxides without the intervention of carbonic oxide or of 

 any other elastic fluid.' I mention these facts because metallurgists are slow to 

 recognise their indebtedness to investigators, and too often ignore the extreme 

 pains with which an accurate knowledge has been acquired of the principles upon 

 which their processes have been based. 



The importance of a coherent explanation of reduction in smelting pig-iron is 

 enormous. The largest blast-furnaces in 1815 hardly exceeded those in use in the 

 previous century, and were at most only 40 feet high witli a capacity of 5,000 

 cubic feet. At the present day their gigantic successors are sometimes 90 feet 

 high with a capacity of 25,000 cubic feet. This development of the blast-furnace 

 is due to the researches of a number of investigators, among whom von Tunner, 

 Lowthian Bell, and Griiner deserve special mention. We are, however, forcibly re- 

 minded of the present incompleteness of our knowledge of the mechanism of reduc- 

 tion, when we remember that the experiments of 11. B. Baker have led us to 

 believe that pure carbon cannot be burnt in perfectly dry and pure oxygen, and 

 therefore that the reducing agent, carbonic oxide, would not be produced at all 

 unless moisture be present. 



Ludwig Mond, Langer, and Quincke teach us not only that nickel can 

 separate carbon from carbonic oxide, but the wholly unexpected fact that dry 

 carbonic oxide can at a temperature of 100° take up nickel, which it again 

 deposits if heated to 150°. Mond and Quincke and, independently, Berthelot, 

 have since proved the existence of the corresponding compound of iron and carbonic 

 oxide, and it may safely be concluded that in the blast-furnace smelting iron this 

 peculiar action of carbonic oxide plays an important part, and it doubtless aids the 

 carburisatiou of iron by cementation. It is truly remarkable that the past year 

 should have brought us so great an increase in our knowledge of what takes place 

 in the reduction of an oxide of iron, and in the carburisation of the liberated 

 metal. My own experiments have, I trust, made it clear that iron can, at an ele- 

 vated temperature, be carburised by the diamond in vacuo ; that is, in the absence 

 of anything more than ' a trace ' of an elastic fluid or of any third element. 

 Osmond has further shown within the last few months that the action between 

 iron and carbon is a mutual one, for though carbon in the pure diamond form car- 

 burises iron, the metal in its turn, at a temperature of 1,0.50°, attacks the diamond, 

 invests it with a black layer, and truly unites with it. 



The question of the direct carburisation of iron (Darby's process) by filtering 

 the molten metal through carbon, promises to be of much importance, for at pre- 

 sent, as is well known, two millions of tons of steel which are made in the 

 Bessemer converter in this country alone, are re-carburised after ' the blow ' by 

 the addition of spiegeleisen. 



Carbonic oxide, moreover, would appear to be more chemically active than had 

 been supposed ; for during the present year Berthelot has shown that the perfectly 

 pure gas heated to .500° or 550° produces carbonic anhydride with deposition of 

 carbon at red heat, not by ordinary dissociation, but by decomposition preceded by 

 polymerisation. He further shows that carbonic oxide will decompose ammoniacal 

 nitrate of silver, and thus brings it into close connection with the aldehydes. 



(2) In turning to the modern aspects of metallurgical practice, we shall see that 

 the whole range of the metallurgist's field of study is changing. It is no longer 

 possible for him to devise a series of operations on the evidence afiforded by a set 

 of equations which indicate the completion of an operation; he has, as I have already 

 suggested, to consider the complicated problems which have been introduced into 



