112 president's address — SECTION B. 



copper loss is 2.02 per cent. Of this total 58 per cent, is incurred in 

 the converting operation and 42 per cent, in the blast-furnacing of 

 slags, linings, &c." Efficient dust-collecting arrangements render the 

 simultaneous silver loss very slight. The direct loss in the converter 

 is only 0.68 per cent. ; but the re-treatment of slags, fluedust, linings, 

 etc., increases this to 1.18 per cent. Here, again, that portion of the 

 total loss which is sustained direct in the vessel is 58 per cent., while 

 the middle-products suffer a loss corresponding to 42 per cent, {i) It 

 will be noted that the direct conversion losses are inconsiderable. In 

 fact, they come within the range of abstractions which may ordinarily 

 be attributed to mere mechanical causes, i.e., short comings of fluedust 

 deposition, &c. The greater direct recovery in silver than in copper 

 follows from the nature of the case. In gold there is a decided plus 

 over the showing of the matte and ore, due to the almost inappreciable 

 loss sustained in the gold assay of ores and mattes. Compared with 

 the very nmch larger quantities handled by the metallurgical plant, 

 this shortage is relatively greater than the actual loss incurred in that 

 plant. Hence the gold recovery apparently — but only apparently — 

 exceeds 100 per cent, as a rule. The ascription to the converter treat- 

 ment of the combined loss in vessel and furnace, as expressed in the 

 higher figures, is obligatory and just. The large amount of middle- 

 products which has to be furnaced, all of them too rich to throw away, 

 is an unavoidable accompaniment of the process ; but, if not worked 

 up, their non-recognition would render the yield quite as unsatisfactory 

 as the early experimentalists deemed it to be. From the nature of 

 the work, the direct vessel output varies a good deal. Copper moves 

 between 95 per cent, and 80 per cent., the balance going into the middle- 

 products. Silver favors higher figures. 



Deficiencies of Present-day Method. — Although the matte -converting 

 process of to-day seems to have reached its climax of perfection, and 

 nothing further appears capable of addition except the use of oxygen, in 

 the chemical direction, and a still further increase in size of apparatus 

 and the well-known desideratum of greater power-efficiency of the 

 machiner}^, in the mechanical direction, it is nevertheless still weak in 

 certain vital metallurgical respects. 



The improvement of the mechanical features may be left to pursue 

 its own course ; but the application of oxygen will probably follow in 

 the wake of its introduction in the steel Bessemerising practice for 

 small charges (" Kleinbessemerei "). It is somewhat singular how the 

 two contemporaneous methods have developed along independent lines, 

 notwithstanding close chemical and intimate mechanical analogy. 

 Even their constructional features have not actually reacted on each 

 other to any tangible extent, notwithstanding the prominence given 

 to the question of side-blowing, &c., in the small steel-converters. 

 However, localised blowing and other points affecting the homogeneity 

 of the steel product are of no interest in copper, on the one hand, and, 

 on the other, the inconvenience caused by the formation of super- 

 abundant slag out of mattes is a point of which the steel practice is 

 (i) The agreement of percentages is purely accidental, and has no signification. 



I 



