1338
is charged from above, through an orifice in the lid of the pot, which is left opetj al ,.•he firing, till the bluish color of the flame shows the volatilization of the w et ’immediately whereupon the hole is covered with a fire-tile m. The iron tubes ,
apt to get obstructed during the distillation, and must therefore be occasionally el eaout with a redhot rod. When the distillation is finished, the iron pipes inuSt /y>urremoved ; the coaly and other contents of the pot cleared away. *A pot lasts aboutmonths upon an average. Five distillations may be made in the course of 14 dal 5 ’^which from 6 to 10 tons of calamine may be worked up, and from 22 to 24 tons ofe°consumed, with a nrnrlne.t of two tons of zinc. The metal amounts to from 25 to 40 I
. floC-
consumed, with a product of two tons of zinc,cent, of the ore.
• 1, 2, is the level of the upper floor ; 3, 4, level of the lower ceiling of the lowerFig. 1232, ground plan on the level of 1, 2 j only one half is here shown. I( | er ,
The-zinc collected in this operation is in the form of drops, and a very fine P°" ., e rmingled with some oxyde. It must be melted in an iron pot or boiler, set in a P r ?f eS .furnace; and the oxyde is skimmed off the surface, to be returned into the cruetThe metal is, lastly, cast into square bars or ingots. j en .
The crucibles are discharged at the end of each operation, by withdrawing the eonser, breaking with a r ake the piece of charcoal which shuts their bottom, and the" e *?*ing them completely, by shaking their upper part. In replacing the condenser-P’F a(see second pot from the right hand, fig. 1230), the flange at its top is covered « j tsring of loam-lute, pressed against the conical bottom of the crucible, and secure^ 1 j.place by means of two parallel rods o, o, which can be clamped by screws projecU n -->zontally from the vertical tunnel. Sej their places, indicated by two open dots n ea w ;,)>A smelter and two laborers are employed in conducting a furnace; who mak 1 ') (g u ra mixture of equal parts of fire-clay, and cement of old pounds finely ground, the P .]{crucibles, which last about four months. Five charges are made in 15 da^ ; the 5e (o!) sup from 6 to 10 tons of calamine, consume from 22 to 24 tons of coals, and produce ^of zinc, upon an average. The following estimate of prices was made a few years »=
3 tons of calamine, at £624 ditto coal, at 5i.
A smelter, at 2 guineas a week -Two laborers, each at 4s. per dayIncidental expenses -
£18
6
2
2
1
£29 18 0 iy
The calamine of Alston moor, used at Sheffield, is not so rich; it produces at B®
25 per cent, of zinc. The coals are laid down at a cost of os. 8 d. per ton ; and the ^mine laid down there 51. ; whence the zinc will amount to 32/. 14s. per ton. a ^-esiderable importations of zinc from Belgium and Germany , for some years hack)caused a considerable fall in its pjice. . [e d, a
At Luttich, where the calamine of Altenberg, near Aix-la-Chapelle , f m ,. 0 ast el1reduction furnace, containing long horizontal earthen tubes, is employed Tie fcokecalamine is finely ground, and mixed with from one third to two thirds its volumeor charcoal, broken to pieces the size of nuts. T erli ca ^
Fig. 1233 represents this zinc furnace in elevation ; and fig. 1234 in a is
section through the middle. From the hearth to the bottom of the cliirnn jj- js
9 feet high, and the chimne) ],.pili18 or 20 feet high, «, ls , u ’ a . A th eb, the grate; c, the fi re P a .’ f tl' ehearth ; c, c, the laborato 5 > j a bo r 'upper arch, which closes in ^flic#
atory; /', the second arch, g>
seconu a j! c *!’ aC e; f’forms the hood-cap of the a whir*!
smelting-house,hearth the flame
the chimney; A, d |e ^ ra "'^ a j| of *h arests against a supporting va uH eThrough the ^
of.the placed iathrough ten flues i,h pairs 0
one line; betwixt these 6t«l of thedraught-openings, upon tube 5 ’
hearth, the undermost earthen^ ^
immediately rest, x 1 . j; e in
third rows of tubes > ’ 0 ther ? j
parallel direction over t j, einch apart;
ge cop a
at
.... ^ th
about one inch »P art » J J\, S . so
row there are only two^tubes^ reS (
ii va* j..--1 iuw ttiv..u * these
there are 22 tubes altogether in one furnace. At their two en