president's address — SECTION B. 105 



ot actual practical importance, where the question of the decompo- 

 sition of the metallic sulphides enters, in the presence of oxygen, the 

 position is governed by the heats of formation of the respective oxides, 

 and the results appear to follow Berthelot's principle of maximum 

 heat. Here copper occupies a subordinate position compared with the 

 metals with which it is commonly associated in mattes — an inferiority 

 which shields it from attack, i.e., scorification, except under the re- 

 versing influence ci relations of mass, &c. This last reservation holds 

 good for the after-blow on white metal, where, if scorification were to 

 ensue, the modicum of iron sulphide present would be powerless to 

 protect the copper. However, in that period, after the removal of 

 the ferrous silicate slag, the roast-reaction taking place is effected 

 wholly independent of the lining, and the latter might as well be basic 

 or neutral. 



In addition to the above, the elective dissociation of the ferrous 

 sulphide, as compared with that of cuprous sulphide, is fostered by the 

 relatively easier elimination of elemental sulphur from it, in high 

 temperatures (even without oxidation), in a neutral atmosphere, 

 which latter must obtain in portions of the bath. The metallic iron 

 simultaneously liberated remains dissolved in the balance of the mono- 

 sulphide. At the fusion temperature of the latter, the vapor tension 

 of sulphur is nearly equal to one atmosphere, and, theoretically at least, 

 it should be possible to fully decompose the compound in vacuo at 

 900° C. {y) This pronounced volatile tendency of the sulphur in com- 

 bination with the iron paves the way for the facile and rapid oxidation 

 of both constituents, in distinction from all other metallic sulphides 

 that come into consideration here as heat-producers. 



A further circumstance shielding the copper from scorification in 

 the slagging period is the more vigorous active part taken by the iron 

 in the formation of a silicate, not only quantitatively, but thermally. 

 For want of specific data on the subject, it is to be assumed, on general 

 evidence, that the heat of formation of cuprous silicates is lower than 

 that of ferrous ones, and that, therefore, ordinarily the latter will form 

 by preference. This particular subject has, however, scarcely been 

 investigated, only the formation heat of the bi-silicate of iron being 

 listed so far. It is to be hoped that we may soon have some informa- 

 tion on the thermo-chemical data of the much more important singulo- 

 silicate, the want of which hampers alike the copper, lead, and nickel 

 metallurgist. 



Review of State of Thermo- Chemical Investigation of Process.— The 

 thermo-chemical investigation of the copper-converting operation in 

 detail, or even with positive satisfaction in rough outline, has not yet 

 been carried out. This is the weak side of all metallurgical knowledge 

 at the present day — an apathetic state of things which will not be 

 remedied until our successors form the habit of currently thinking in 

 terms of physical chemistry. Some crude approximations, not tied 

 to the full analytical data of any one or any series of observations in 



(y) H. Le Chatelier and Ziegler, " Sulfur de Fer, &c.," Bull. Soc. d'Encourag., 1902 ; 

 also, von Jiiptner, " Grundziige der Siderologie," 1904, III., p. 98. 



