president's address — SECTION B. 75 



therefore forced itself on the minds of the experimenters that the second 

 stage was impracticable. In reality the reason was the employment 

 of too small a quantity of matte, had they but known it ; for a heavier 

 yield of metallic copper would have permitted of pouring some of this 

 metal, instead of its sticking to the lining in toto. 



The chemical reactions von Jossa and Laletin explain elaborately, 

 but on assumptions that violate the chemical feeling of to-day, by 

 introducing the formation of sulphates. They recognised that there 

 was no special {i.e., no chemical) copper loss during the slagging period, 

 their analyses not showing more than 1 per cent, copper in the oxidised 

 form. The slag, however, became injuriously rich during the second 

 period, or the after-blow. Had they continued their experiments 

 there can be no doubt that this point, as well as others which seemed 

 to argue against the process, but which were mainly the results of 

 mechanical difficulties, would have been fully overcome, for these two 

 engineers had the great advantage over the ordinary copper metallurgist 

 of the day, of manipulative familiarity with steel-converting. The 

 general course of the chemical reactions they identified as similar to 

 those of the Welsh process, except for the very decided gain in time and 

 intensity. 



The tests made with the combined injection of steam and air 

 yielded no conclusive results, whether \\\q former was admitted con- 

 tinuously or intermittently. The general phenomena were the same 

 as in air-blowing, except that the projection of molten material was 

 greater, which may have been due to the greater pressure employed 

 (lOlbs. to 121b«.), and the slags cooled more quickly. The operation 

 was stopped after 10 to 15 minutes of blowing, on the appearance of 

 the color change in the flame ; but the matte only assayed 63 per cent, 

 to 66 per cent, of copper, while the slags contained 6.5 per cent, to 9 per 

 cent, of copper, principally mechanically included. The sulphur in this 

 matte was found very low, viz., 18 per cent, to 19 per cent., and its 

 composition indicated the presence of considerable metallic iron, which 

 the experimenters regarded as alloyed with the metallic copper. The 

 reason of the failure of steam-blowing was given as lying in the lowness- 

 of the temperature of the oxidising reactions involved, and which did 

 not permit of an energetic reaction between the steam and the sulphides. 

 According to Regnault, a white heat is necessary for the formation of 

 metallic copper out of cuprous sulphide in a current of steam — at lower 

 temperatures there is scarcely a reaction. The temperature in the 

 retort, they stated, even with air alone, did not reach this point, and 

 the combustion of the iron was hampered in the creation of a high pyro- 

 metric intensity for an analogous reason. The conclusion they came 

 to was that the application of steam, with or without air, has no chemical 

 or economical advantages. 



Reviewing their results as a whole, von Jossa and Laletin drew 

 the following conclusions : — 



1. The Bessemerising of copper mattes by means of superheated 

 steam alone, or together with an air-blast, for the production of black 

 copper, is scarcely practicable. 



