METALLURGY. (PROCESSES.) 



361 



elevation, it has been suggested that advantages 

 might be gained in reduction processes by work- 

 ing under pressure, and notably an economy of 

 time. By thermal calculations it is shown that 

 if reduction be effected at a pressure of one at- 

 mosphere above the normal, the time of reduction 

 may be shortened by one-half, the external heat 

 applied being of course increased in correspond- 

 ence with the lessening of the time, and the. ore 

 being sufficiently finely crushed to allow of the 

 reaction being completed in the shorter period. 

 By doubling the difference of temperature between 

 the inside and the outside of the reduction ves- 

 sel, the time of reduction may again be shortened 

 one-half. Such a pressure furnace (working at 

 + 1 atmosphere pressure) has been tried by Bes- 

 semer. Cast steel has been made experimentally 

 in a similar way at a Westphalian works. 



The process of magnetic concentration of ores 

 of Messrs. Ettinger & Co. is based on the fact that 

 all substances behave differently under the influ- 

 ence of a strong magnetic current. The machine 

 employed consists essentially of tw r o parallel bar 

 electro-magnets, one above the other, the upper 

 one being cylindrical and the lower one either 

 cylindrical or semicylindrical. The ore to be tested 

 is fed in a crushed condition between the poles of 

 the magnets by means of an adjustable inclined 

 shoot, slightly pressed by a spring against the 

 upper cylinder. The paramagnetic particles ad- 

 hering to the cylinder are carried round by its 

 rotary movement, and faintly magnetic particles 

 soon reach a point where centrifugal force and 

 gravitation overcome magnetic attraction, and 

 consequently drop into a shoot prepared to receive 

 them. In the meantime, the more highly magnetic 

 particles, adhering longer to the revolving cylin- 

 der, drop into another shoot placed farther from 

 it. The following minerals are separated in this 

 way: magnetic ores, all iron ores, compounds of 

 titanium, tungsten, nickel, cobalt, and manga- 

 nese, oxidized and sulfid ores of copper and 

 certain sulfids of zinc, lead and silver ores, tin 

 ores, and compounds of bismuth. The advantages 

 claimed for this machine are the large output, 

 slight liability to wear and tear, and the slight 

 expenditure of electrical force involved. 



The Phoenix process of sulfid-ore treatment, de- 

 scribed by Mr. E. A. Ashbridge before the Insti- 

 tute of Mining and Metallurgy, consists of a cycle 

 of four main operations. The first is the dis- 

 placement of the sulfur combined with the metals 

 in the ore, by means of chlorin gas; this is done 

 in a converter, to which the ore, mixed with fused 

 zinc chlorid, is introduced at a suitable heat at 

 the top, while the dry gas is injected from below. 

 The chlorids of sulfur being produced only at 

 low temperatures, the action is carried on at a 

 heat of at least 650 C., whereby sulfur is vapor- 

 ized and carried away for condensation, while 

 fused chlorids of metals mixed with silicious 

 gangue remain behind and are tapped. The sul- 

 fur, with which is associated a small quantity of 

 chlorids, chiefly of iron and zinc, is washed with 

 water to purify it. The second step is the desil- 

 verization of the residiie, with the production of 

 argentiferous lead, and the separation of the re- 

 mainder of the lead from the mixed chlorids. 

 This is done by adding zinc, which throws dow r n 

 the lead from the fused chlorids, or by electrolysis. 

 The third operation is the separation of the sili- 

 cious gangue (which is unacted on) from the zinc 

 chlorid by settlement and decantation, the gangue 

 being freed from the chlorid by washing with 

 water or by distillation the former being prefer- 

 able. The final chlorid is purified, the wash 

 chlorid solutions are boiled down, and the whole 



of the zinc chlorid is prepared for 1 h.- [<>uri h opera- 

 tion of electrolysis. Hereby the /.'me i n-eo ered 

 as metal, and the chlorin is pumped ! , ; f or 

 reuse with fresh ore in the first operation. 



The-older methods of niariufaetm ii' 

 by drawing, rolling, or bending over ;i ., 

 were in time superseded by the lead-pipe 

 in which molten lead is placed in a healed 

 tainer, and when cooled down to plastie'nv is 

 forced through a die by hydraulic pressure/ I'.y 

 this means, instead of only short lengths of pipe 

 being made, as with the old methods, pipes of any 

 required length are produced. In the improved 

 press of Mr. Alexander Wylie, the container, in- 

 stead of being kept hot by a fire or a ring of gas- 

 jets, is jacketed and steam-heated. In an impor- 

 tant adaptation of this press to the encasing of 

 telegraph-cables, the cable passes horizontally 

 through a case, and the covering is done continu- 

 ously, rapidly, and effectively. By the extension 

 process of Mr. Alexander Dick, all kinds of bars, 

 from a simple round wire to complex sections 

 which it is impossible to roll, and tubes of any 

 section are produced by causing metal heated to 

 plasticity to flow through a die under hydraulic 

 pressure. This process consists in charging the 

 hot metal into a horizontal container, at the front 

 and rear of which is the die. Upon hydraulic pres- 

 sure being applied at the rear end of the con- 

 tainer, the plastic metal is forced through the 

 die, issuing therefrom as bars and tubes. The 

 quality of the metal is greatly improved in the 

 bars thus produced. It acquires increased density 

 and is perfectly homogeneous. Extended bars of 

 given lengths yield higher results under test for 

 tensile strength than rolled bars of the same 

 metal, and it works better in the lathe or screw- 

 ing machine at speeds twice or even three times 

 as great as those employed with ordinary metal. 

 Mr. Dick's process is likewise applied to copper 

 and its alloys, but these metals are operated on 

 at a far higher temperature. 



A method has been devised by Mr. Thomas A. 

 Edison for obtaining a more permanent phono- 

 graphic record than the wonted one by means 

 of gold plating. The wax cylinder carrying the 

 record is revolved in a vacuum between two gold 

 electrodes. A vacuum discharge is passed, and 

 the gold is deposited. By electrodeposition the 

 layer of gold is backed up with copper, and the 

 wax is then melted off'. A deposit of silver is then 

 electrolytically laid upon the copper matrix, and 

 as soon as the silver layer is of the required 

 thickness the copper is dissolved off. There is 

 thus left a silver deposit containing a thin layer 

 of gold, and the record is, it is hoped, an exact 

 reproduction of the original \vax; but its exact- 

 ness has not yet been fully tested. 



The Riecken process for treating tellurid and 

 sulfid ores is an electrochemical system* for the 

 recovery of the various metals from ores by a 

 single operation, without resorting to filtration. 

 The machinery consists of an open iron tank with 

 vertical ends, inclined sides, and rounding bot- 

 tom. The tank is provided with a horizontal 

 shaft passing through stuffing-boxes at each end, 

 also with proper beaters to agitate the contents 

 of the vat, and with suitable gear-wheels outside 

 of the tank for rotation. The bottom and sides 

 of the tank are lined with removable amalga- 

 mated copper plates, and form the negative pole 

 of the circuit, the positive pole being stationary. 

 By means of a small force-pump a stream of mer- 

 cury is caused to flow continually over these 

 amalgamated plates, which, running down into 

 the bottom of the vat, is drawn off through a 

 mercury tap and again elevated by the pump, 



