316 
SCIENCE. 
the modified medium-sized dynamo-machine, capable 
of producing 36 webers of current with an expenditure 
of 4 horse-power, and which, if used for illuminating 
purposes, produces a light equal to 6000 candles, I find 
that a crucible of about 20 centimetres in depth, immersed 
in a non-conductive material, is raised up to white heat 
in less than a quarter of an hour, and the fusion of one 
kilometre of steel is effected within, say, another quarter 
of an hour, successive fusions being made in somewhat 
diminishing intervals of time. It is quite feasible to 
carry on this process upon a still larger scale by increas- 
ing the power of ihe dynamo-elec rtc machine and the 
size of the crucibles. 
By the use of a pole of dense carbon, the otherwise 
purely chemical reaction intended to be carried into effect 
may be interfered with through the detachment of parti- 
cles of carbon from the same ; and although the con- 
sumption of the negative pole in a neutral atmosphere is 
exceedingly slow, it may become necessary to substitute 
for the same a negative pole so constituted as not to 
yield any substance to the arc. I have used for this pur- 
pose (as also in the construction of electric lamps) a 
water pole or tube of copper, through which a cooling 
current of water is made to circulate, ft consists simply 
of a stout copper cylinder closed at the lower end, having 
an inner tube penetrating to near the bottom for the 
passage of a current of water into the cylinder, which 
water enters and is discharged by means of flexible india- 
rubber tubing. This tubing being of non-conductive 
material, and of small sectional area, the escape of cur- 
rent from the pole to the reservoir is so slight that it may 
be entirely neglected. On the other hand, some loss of 
heat is incurred through conduction in the use of the 
water pole, but this loss diminishes with the increasing 
heat of the furnace, inasmuch as the arc becomes longer, 
and the pole is retired more and more into the crucible 
cover. 
To melt a gram of steel in the electric furnace takes, 
it is calculated, 8100 heat units, which is within a frac- 
tion the heat actually contained in a gram of pure carbon, 
ft results from this calculation that, through the use of 
the dynamo-electric machine, worked by a steam engine, 
when considered theoretically, 1 lb. of coal is capable of 
melting nearly 1 lb. of mild steel. To melt a ton of steel 
in crucibles in the ordinary air furnace used at Sheffield, 
from to 3 tons of best Durham coke are consumed ; 
the same effect is produced with 1 ton of coal when the 
crucibles are heated in the Regenerative Gas Furnace, 
whilst to produce mild steel in large masses on the open 
hearth of this furnace, 12 cwts. of coal suffice to produce 
1 ton of steel. The electric furnace may be therefore 
considered as being more economical than the ordinary 
air furnace, and would, barring some incidental losses 
not included in the calculation, be as regards economy 
of fuel nearly equal to the Regenerative Gas Furnace. 
It has, however, the following advantages in its favor: 
1st. That the degree of temperature attainable is theo- 
retically unlimited. 2d. That fusion is effected in a per- 
fectly neutral atmosphere. 3d. That the operation can 
be carried on in a laboratory without much preparation, 
and under the eye of the operator. 4th. That the limit 
of heat practically attainable with the use of ordinary re- 
fractory materials is very high, because in the electric 
furnace the fusing material is at a higher temperature 
toan the crucible, whereas in ordinary fusion the temper- 
a'ure of the crucible exceeds that of the material fused 
within it. 
Without wishing to pretend that the electric furnace 
here represented is in a condition to supersede other 
furnaces for ordinary purposes, the advantages above in- 
dicated will make it a useful agent. I believe, for carrying 
on chemical reactions of various kinds at temperatures 
and under conditions which it has hitherto been impos- 
sible to secure. 
DESILVER 1 ZATION OF LEAD BY THE ZINC 
PROCESS. * 
By J. E. Stoddart. 
The treatment of argentiferous leads with zinc, for the 
purpose of extracting the silver and refining the lead, is by 
no means a novel process. About twenty years ago a 
metallurgist named Parks took out patents for desilverizing 
rich leads by means of zinc, and a manufacturing firm 
adopted his process. They were, however, subsequently 
obliged to abandon it, in consequence of the difficulty ex- 
perienced in the separation of the zinc from the concen- 
trated silver, to admit of the cupellation of the latter metal. 
A German chemist named Flach afterwards took up the 
subject, and by running the alloy of zinc, silver, and lead 
along with iron slag, through a peculiarly constructed 
blast-furnace, was enabled to free the concentrated silver- 
lead from zinc. He also proposed the use of this furnace 
for removing of traces of zinc from the desilverized lead, 
but this was abandoned in favor of the ordinary im- 
proving or calcining pan. The operation with the blast- 
furnace was found to be very troublesome, and as the 
greater portion of the zinc was entirely lost, was by no 
means economical. M. Manes, of Messrs. Guillem & Co., 
Marseilles, who were the first to work Flach’s process, 
found out and patented a simple means of treating the 
alloy, and recovering the zinc by distillation. This is the 
process now in use and known as the Flach-Guillem pro- 
cess, and which is carried on in the following manner : — 
About 18 tons of “rich lead,’" containing generally from 60 
to 70 ounces of silver per ton, are melted in a large cast-iron 
pot, to which 1 percent, by weight of zinc is added, and the 
whole well stirred for twenty minutes. The fires are drawn, 
and the contents allowed to settle and cool until the zinc 
rises to the surface, and forms a solid ring or crust con- 
taining the silver and other foreign metals. This alloy is 
removed to a small pot at hand, where part of the lead is 
sweated out, and the alloy thoroughly dried. The large pot 
with the lead now partially desilverized is again heated up, 
and treated in the same way as before, but with the addition 
of only a half per cent, of zinc, which when it has risen to 
the top is removed as before, and dried. A third addition 
of a quarter of per cent, of zinc is found necessary to take 
out the remainder of the silver, care being taken, on the 
cooling of this zincing, that all the crystals are cleanly 
skimmed off. The lead in the large pot is assayed, and 
found almost always to contain less than 5 dwts. of silverto 
the ton of lead ; if it should happen to contain more, it is 
due to carelessness on the part of the workmen. The pot 
is now tapped, and the lead run down into an improving 
pan, where it is kept at a high heat for nearly eight hours, 
for the purpose of oxidising or burning off the small per- 
centage of zinc which is left in it from the zincing process ; 
after seven or eight hours’ firing in this pan it should con- 
tain no trace of zinc. It is then tapped and run into moulds 
for market lead, or for the manufacture of lead products. 
The old improving pans were made of cast-iron, placed on a 
bed of sand, with a groove in the upper sides, which groove 
was filled with bone-ash to prevent the action of oxide of 
lead on the iron. These pans, from the giving way of the 
bone-ash, and the great wear and tear on the iron from the 
high heats necessary, were found to be both troublesome 
and expensive ; they were very often under repair, and 
seldom lasted more than six or eight months. They have 
been superseded by an improving pan of cast-iron lined 
with brick inside. This pan, instead of being placed on a 
bed of sand, as was the case with the old improving pan, 
is hung on brick walls, and is quite open both below and 
round the outside. This new pan has been working in 
the patentee’s works, Marseilles, for some years without 
any break down. It burns no more coal, and can be as 
economically worked in every way as the old pans. The 
zinc and silver allojq after being dried, is melted in a 
plumbago crucible, covered on the top, well luted with 
fire clay, connected with a small cast iron receiver by 
means of a plumbago pipe, and fired up with coke. The 
zinc, distils over, and is condensed in the iron receiver. 
After all the zinc has been distilled, the pipe is discon- 
nected, the cover removed, and the lead and silver, left in 
* Read before the Philosophical Society of Glasgow, Nov. 8, 1880. 
