METALLURGY. 



521 



as the bloom is removed and the hearth is 

 cleaned oat, it is again closed and refilled with 

 charcoal and iron, by raking down from the 

 shaft as before, and the blast is turned on. In 

 the same way, the process may he alternated 

 with the other hearths. A considerable ad- 

 vantage to the practical utility of this furnace 

 is the great ease with which the raking-down, 

 or any other operation which may be required 

 in the hearth while the blast is on, is effected. 

 With a little practice, which an unskilled la- 

 borer may acquire in a very short time, it is 

 possible to charge and rake charcoal and ores 

 uniformly down, an advantage embodying a 

 check whereby, to a certain extent, the action 

 in the furnace may be kept perfectly even. 

 The heat thrown out by the furnace was small, 

 and the work of operating it was so simple as 

 to render the managers comparatively inde- 

 pendent of skilled workmen. In most of the 

 experiments two barrels, or 12'6 cubic feet, of 

 charcoal to 3 cwt. of ore were used ; but toward 

 the finish, the quantity of ore was reduced to 

 2 cwt. When tested, the iron made by this 

 process did not show any tendency to red- 

 shortness or brittleness; its elasticity was satis- 

 factory and compared well with that of the 

 class of pig-iron made by the Lancashire pro- 

 cess. The process is well adapted to resmelt- 

 ing by the Martin process. According to Prof. 

 Sarastrom's estimates, 15 tons of good merchant 

 iron, containing an average of 0'08 of phos- 

 phorus, were made by it from 27 tons of ore 

 containing 0*91 of phosphorus, with an expen- 

 diture of about 600 barrels of charcoal and a 

 loss of iron amounting to less than 5 per cent. 

 In Bull's direct process, no solid carbon is 

 used in the furnace. The charge is made with 

 iron - ore and flux usually limestone only, 

 while the furnace is worked exclusively with 

 gas, which is delivered to it in a very highly 

 heated state direct from the producers. Highly 

 heated air is also introduced in sufficient quan- 

 tities to burn about 10 per cent, of the gas and 

 maintain the furnace at the high temperature 

 necessary to allow the -withdrawal of the iron 

 or steel and cinder in a fluid state. The gases 

 rising through the ore and flux under this sys- 

 tem are carbonic oxide and hydrogen in equal 

 volumes, together with the nitrogen derived 

 from the air which has been blown into the 

 furnace. These gases being produced entirely 

 outside of the furnace, there is no zone of gasi- 

 fication within it, but only the zones of fusion, 

 reduction, and carbonization have to be pro- 

 vided for. The zone of preparation, in which 

 the ore, fuel, and flux are freed from their moist- 

 ure and the temperature of the ore is raised 

 to the reduction-point, is also removed from 

 the furnace to a special apparatus. Experi- 

 ments in the operation of this system were 

 made by the Societe John Cockerill at Sera- 

 ing, Belgium, in 1881. With an ordinary blast- 

 furnace six feet in diameter at the base, and 

 twenty-one feet high, it was found possible to 

 reduce the silicon in the product from 3'40 to 



15 ; the sulphur from 1-61 to -33 ; the phos- 

 phorus from 1-76 to 1*10; the manganese to nil; 

 the combined carbon to - 52 ; and the graphite 

 to '17. At the same time, the output from the 

 furnace was increased enormously, and the 

 quantity of fuel required was decreased in a 

 corresponding ratio. Mr. Bull has not yet 

 erected his furnace on a commercial scale, but 

 is awaiting the perfection of improvements in 

 his calcining oven for heating the ore and flux, 

 and in the air-heating stoves and gas-producers. 

 He is confident, however, that with the enor- 

 mous increase of the output of the furnace and 

 the great reduction in the amount of fuel con- 

 sumed, which he has demonstrated, iron or 

 steel ingots can be produced by his system in 

 any district at a cost much lower than the most 

 inferior pig iron under the present systems. 



Lead and Silver. Mr. Carl Henrich, while 

 smelting at the Benson Smelting Works in Ari- 

 zona, for lead-silver bullion, had to use as a lead- 

 ore a sulphate of lead (anglesite) with occasional 

 lumps of galena. He had also received for re- 

 duction an ore high in silver, carrying about 

 25 per cent, of iron pyrites, with oxide of iron 

 and quartz or silicates. Finding the old meth- 

 od of reducing anglesite to sulphide of lead and 

 then precipitating the lead by metallic iron to 

 be very unsatisfactory, on account of the quan- 

 tity of silver-bearing matte produced, and the 

 difficulty, amounting almost to an impossibil- 

 ity, of making a slag free from lead, he made 

 the experiment of reducing the anglesite by 

 the action of iron pyrites with silica. Acting 

 upon the calculation that the reducing power 

 of the pyrites would be about five times that 

 of the galena, he found that, by putting togeth- 

 er, in round numbers, 350 pounds of the angle- 

 site ore (estimated to contain 15 per cent, of 

 galena and 75 per cent, of anglesite) with 100 

 pounds of the silver- ore carrying iron pyrites, 

 the two ores would reduce each other and the 

 sulphur would be removed in the form of sul- 

 phurous acid (S0 2 ), with the production of very 

 little matte. 



Copper. Heap-roasting of copper-bearing py- 

 rites has been practiced at nine different mines 

 lying along the ore belt from North Alabama to 

 Central Vermont, but can be said to have en- 

 tirely succeeded only at two neighboring mines 

 lying in Central Vermont. The bed upon which 

 the ore is roasted, having to be well drained, 

 is constructed precisely like the traffic-way of 

 a city street. The plan of the heap is laid off 

 in the form of a parallelogram, 24 feet wide 

 and 50 feet long, and wood common split 

 fuel-wood is the best is piled nine inches deep 

 all over the plan. The ore is piled upon this 

 and carefully arranged in successive layers till, 

 a bed seven feet thick is formed. One foot of 

 " ragging," or the coarser part of ore that has 

 passed through a screen of holes 1 inch in 

 diameter, is laid over this, and the fire is start- 

 ed. As soon as the ore has ignited, from the 

 ground one foot upward, "fines," or that part 

 of the ore which has passed through a screen 



