62 president's address — section b. 



Now, the behaviour of the metals towards oxygen is controlled 

 by their degree of affinity for that element, and this degree is definitely 

 expressed by the heats of formation of the respective oxides. If the 

 heat evolved is insufficient for the purpose of maintaining the resulting 

 solid products of the operation in a molten condition, then no fusion 

 will result, and the segregation of these solid products from each other, 

 which can only be acliieved by ordinary physical means, i.e.. gravity, 

 cannot be effected. Fortunately, the heats of formation of the oxides 

 of both iron and sulphur, though not great, are fully sufficient for 

 bringing about this physical desideratum, especially when advantage 

 is taken of the circumstances that temperature of combustion increases 

 with pressure, and that temperature and the degree of concentration 

 of the reacting bodies directly accelerate the velocity of chemical 

 reaction itself. Conversely, therefore, the time element is a vital 

 factor in oxidation processes if a separation of the products by purely 

 physical means is desired, such as by differences of specific gravity, 

 which constitute so important a feature of smelting processes in general. 

 The necessity of concentrating the reactions involved into a minimum 

 of time, and, it may also be added, as far as the gaseous oxidising 

 agent is concerned, into a minimum of space, is thus obvious. Under 

 all circumstances, whether oxidation proceeds slowly or rapidly, only 

 the same amount of heat is generated. But its dilution, so to say, 

 by spreading it over long periods of time, is inimical to the attainment 

 of a pyrometric intensity reaching and surpassing the fusion points 

 of the solid (not gaseous) products involved. 



However, these observations are premature as far as the history 

 of our subject is concerned. The facts embodied in them were not 

 inferred for a long while, even from the data which the early thermo- 

 chemical researches of the second and third decades of the last century 

 afforded. Thus the thermal value of iron, among other elements, 

 was determined by Despretz in 1827. The posthumous writings of 

 Dulong, in 1838, gave exacter results for iron, sulphur, copper, zinc, 

 tin, &c., and were followed by Hess (1840), and the still more refined 

 researches of Andrews {ca 1848) on these and other elements of direct 

 bearing on our subject, out of the number of those investigated. Sub- 

 sequently Favre and Silbermann (1852-3) added their comprehensive 

 and still largely authoritative figures for a much more extensive list, 

 though in the meantime many of their results have also been corrected, 

 Thomsen (1853-1886), Berthelot, and others of the more recent thermo- 

 chemists adding enhanced reliability by the employment of more perfect 

 calorimetric methods and apparatus. All this information, however, 

 remained for the curious and the theoretically inclined. The metal- 

 lurgical practitioners, with typical supineness, allowed it to go unheeded 

 until the early seventies, Avhen the first calculations of the thermal 

 energy inherent in sulphide ores and furnace products make their 

 appearance in literature (Bode). Even the first practical large scale 

 attempts towards the rapid oxidation of copper iron sulphides (1867-8) 

 — of which the general idea was suggested by the sustained success of 

 the Bessemer steel-conversion process, the source of heat in which 



