PRESIDENTS ADDRESS — SECTION B. 113 



fortunately free. Hence there has been no similarity of difficulties. 

 A further significant difierence influencing the rationale of the 

 work, and tending to alienate the two methods, is one bearing 

 on the duration of the blows, there being only some 5 per cent, 

 to 10 per cent, of substances to oxidise in cast iron, while in mattes 

 from 40 per cent, to 65 per cent, of the constituents have to be burnt, 

 and this must be done in two stages. However, it is fair to assume 

 that the accelerating influence of the use of oxygen will bring the two 

 methods nearer together, to the benefit of the treatment of our own 

 metal. 



There is, however, a direction in which, doubtless, the pneumatic 

 treatment of mattes up to the white metal stage is capable of improve- 

 ment, and that is the means and conditions which now control the 

 chemical process of the first period, i.e., the slag-formation. Of all 

 apparatus for the mere scorification of iron by the heat of iron and 

 sulphur, the converter is the least suitable in point of efficiency and 

 capacity. We have already discussed the question of linings, and the 

 desirableness of avoiding the latter altogether by the introduction of 

 silicious material from the outside. The conclusion was arrived at 

 that the converter should not properly be used for smelting purposes 

 which can be otherwise achieved, and the same conclusion holds in the 

 connection now broached. The converter vessel, even when ulti- 

 mately provided with suitable vertical or bottom tuyeres, as is the 

 hope of American adepts, and efficient as it is in point of absorption 

 or utilisation of the oxygen in the blast, is still tainted with the defect 

 of unnecessarily prolonging the pneumatic action, and thus lowering 

 the thermal effect. 



There are three ways of accomplishing the oxidation of the iron in 

 the matte : by injection of a current of blast into the body of matte ; 

 by percolation of the matte through the current of blast ; and by 

 projecting the blast on to the body of the matte, and providing means 

 for the constant presentation of a new" surface. In each case the rapidity 

 and completeness of the scorification will depend upon the particular 

 degree of intimacy of mechanical contact between the nascent oxide 

 and the silica which the conditions permit. 



The first-mentioned case is that of the present method, the silica 

 constituting the containing vessel. It is obvious that, between the 

 oxidation of the iron and its union with the substance of that vessel, 

 the bulk of the particles oxidised must suffer a period of chemical 

 inertness, however short under the circumstances, during which they 

 are on the hunt for their respective particles of silica on the surface of 

 the surrounding lining. The general consequence is a delay in the 

 scorification, which means a delay in the formation of protoxide, the 

 two being coincident. It is likely that a higher oxide momentarily forms 

 in the absence of silica, which, for the unit weight of oxygen, produces 

 less heat than the protoxide, though more for the unit weight of iron. 

 At the final moment of contact with silica this higher oxide would be 

 reduced by the ferrous sulphide, and scorification effected, with the 

 associated greater evolution of heat. In any case, however, the com- 



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