president's address — SECTION B. 101 



sulphur is available for oxidation during this period which is not bound 

 as cuprous sulphide. Tlie rest is comraonly a,ssuraed to he combined 

 with iron as protosulphide, notwithstanding that it has been long known 

 that there is practically always a shortage of sulphur for this piu-pose, 

 and which gave rise to the supposition that mattes contained lower 

 sulphides of iron — a view no longer held. Generally speaking, the first 

 10 minutes or so at the beginning of the blow are the most interesting 

 in regard to the iron, the average percentage of sulphurous acid in the 

 gases by volume then running up from only 1 per cent, to 10 per cent, 

 within that time. Thereafter it remains at about the latter figure up 

 to the end of the slagging, while, simultaneously, the free oxygen in 

 the gases ranges from mere traces in the first 10 minutes to only J per 

 cent, for the rest of the period, with an occasional 3 per cent, (all by 

 volume). If the iron and sulphur contained in the protosulphide of 

 a 50 per cent, matte were equally oxidised, then about one-third of 

 the oxygen of the blast should go to the iron, and about two-thirds to 

 the sulphur, and the escaping gas should contain 1-5 per cent, by volume 

 of sulphurous acid. It, however, contains only 10 per cent., and, at 

 the same time, only a trace of oxygen or free air. It is thus obvious 

 that relatively more of the iron is oxidised than of the sulphur in the 

 monosulphide, assuming that all the iron is present in this condition. 

 In am' case, sulphur takes second place for a part of the slagging period. 

 It is also likely that portion of the sulphur is driven out in the elemental 

 state, without oxidation within the vessel. The protosulphide acts in 

 this manner in the pyrite furnace, and the conditions in both apparatus 

 are fundamenta,lly identical. 



Subsequently, during the afterblow, the sulphurous acid increases 

 up to over 18 per cent, by volume, with a simultaneous 0.5 per cent, 

 of oxygen, and it is only during the last few minutes of the finish that 

 the oxygen may reach '2 per cent, to 8 per cent, or over. It is only 

 here, then, during the whole process, that, in good practice, an excess 

 of air can be said to escape from the converter. Yet the dire effects 

 of such an ( assumed) excess were once greatly feared, both in the 

 pneumatic treatment of mattes in the converter and of p}Titic ores 

 in the blast furnace I 



One important circumstance which assists in explaining the pre- 

 ferential oxidation of th.e iron, as compared with the sulphur, is that 

 the total iron and its associated sulphur present in mattes stand in the 

 relation to each other of a compound which actually contains less 

 sulphur than ferrous sulphide and more iron. This phenomenon is 

 the outcome of the decomposition of the true ferrous sulphide, by mere 

 heat, in the smelting operation from which the matte is derived, the 

 particular iron sulphur compound which results depending on the 

 temperature, pressure, &c., of the matting operation. It, however, 

 probably always contains free iron. In fact it maybe regarded, for all 

 practical purposes, as consisting of true ferrous sulphide plus metallic 

 iron. Now, undoubtedly the oxidation of this uncombincd iron takes 

 place instantly from the commencement of the blow, the combustion 

 of the real protosulphide being relegated to a secondary position during 



