102 PEESIDENT's address — SECTION B. 



the whole period, though quite concurrent with the other. The oxida- 

 tion of the protosulphide requires its prehminary decomposition, which, 

 besides demanding heat, also takes time. The oxidation of free iron 

 is not thus hampered, and its preferential combustion must be especially 

 marked when its amount is considerable. As is well known, most 

 mattes contain it to a suificient extent for it to be shed out of the 

 solution on cooling to a degree more or less manifest to the magnet, 

 and even the naked eye. 



But even on general thermo-chemical lines it should be obvious 

 that the iron will be disposed to take the part of the main fuel, even to 

 the extent of the elimination of portion of its concomitant sulphur 

 without oxidation. The position is simply that all pneumatic processes,, 

 to be rightly weighed, should be regarded from a point of view accepting 

 the or.iji]en as the active agent in the combustion process, not the fuels 

 themselves. It is the gaseous oxygen, while it traverses the molten 

 mass, which seeks combination, and not really so directly either the 

 iron or the sulphur, since these are combined with each other. And 

 while on this search the oxygen necessarily exercises a discriminating 

 or selective action. It prefers that element of the two present with 

 which it can generate the greater amount of thermal energy. Berthelot's 

 law of maximum heat, though not absolutely correct, covers the case. 

 But when the position is thus viewed from the standpoint of the oxygen, 

 our valuation of the calorific importance of the combustible elements 

 is liable to be subverted from its ordinary plane. What is meant will 

 become clear from the remark, for instance, that although the heat of 

 formation of ferrous oxide in terms of iron is 1,220 calories and that of 

 carbonic acid in terms of carbon 8,080 calories, still one kilogram of 

 oxygen combining with iron to protoxide yields 4,270 calories, and with 

 carbon to carbonic acid only 3,030 calories. In terms of oxygen or air, 

 therefore, the fuel values of iron and carbon are quite inverted from 

 the positions they occupy in the popular judgment. And there is a 

 similar incongruity between iron and sulphur. In terms of the unit 

 weight of these substances, the heats of formation of the protoxide and 

 of sulphurous acid are respectively 1,220 and 2,221 calories. Expressed 

 in terms of oxygen they are respectively 4,270 and 2,221 calories — the 

 same weight of atmospheric oxygen, therefore, giving about twice as 

 much heat when burning the iron in the matte as when burning the 

 corresponding sulphur. This contrast of figures will serve roughly to 

 indicate the position in the converter, without going into further 

 details. The air admitted has full sway to satisfy its selective ten- 

 dencies in an excess of sulphide, and, for the reasons mentioned, and 

 certain others springing from the properties of iron sulphide in high 

 temperatures, which tend to impede the oxidation of the sulphur, it 

 no doubt does so. Even under less energetic conditions, such as those 

 of ordinary temperature and atmospheric pressure, it is true that 

 ferrous sulphide acts quite the same — the iron oxidises to ferric oxide, 

 but the sulphur is simply discarded in the elemental state, unoxidised.(a;) 



{x) A. Wagner, Dingier Jl., 1870, vol. 192 : also. Prof. Pollacci, Intemat. Congr. 

 Appl. Cheui- Rome. 1906 



