1. _Native quicksilver._--It occurs in most of the mines of the other
mercurial ores, in the form of small drops attached to the rocks, or
lodged in the crevices of other ores.
2. _Argental mercury, or native silver amalgam._--It has a silver-white
colour, and is more or less soft, according to the proportion which the
mercury bears to the silver. Its density is sometimes so high as 14. A
moderate heat dissipates the mercury, and leaves the silver. Klaproth
states its constituents at silver 36, and mercury 64, in 100; but
Cordier makes them to be, 27-1/2 silver, and 72-1/2 mercury. It occurs
crystallized in a variety of forms. It has been found in the territory
of Deux-Ponts, at Rozenau and Niderstana, in Hungary, in a canton of
Tyrol, at Sahlberg in Sweden, at Kolyvan in Siberia, and at Allémont in
Dauphiny; in small quantity at Almaden in Spain, and at Idria in
Carniola. By the chemical union of the mercury with the silver, the
amalgam, which should by calculation have a spec. grav. of only 12·5,
acquires that of 14·11, according to M. Cordier.
3. _Sulphuret of mercury_, commonly called Cinnabar, is a red mineral of
various shades; burning at the blowpipe with a blue flame, volatilizing
entirely with the smell of burning sulphur, and giving a quicksilver
coating to a plate of copper held in the fumes. Even the powder of
cinnabar rubbed on copper whitens it. Its density varies from 6·9 to
10·2. It becomes negatively electrical by friction. Analysed by
Klaproth, it was found to consist of mercury 84·5, sulphur 14·75. Its
composition, viewed as a bisulphuret of mercury, is, mercury 86·2,
sulphur 13·8. The finest crystals of sulphuret of mercury come from
China, and Almaden in Spain. These contain, according to Klaproth, 85
per cent. of mercury.
A _bituminous sulphuret of mercury_ appears to be the base of the great
exploration of Idria; it is of a dark liver-red hue; and of a slaty
texture, with straight or twisted plates. It exists in large masses in
the bituminous schists of Idria. M. Beurard mentions also the locality
of Munster-Appel, in the duchy of Deux-Ponts, where the ore includes
impressions of fishes, curiously spotted with cinnabar.
The compact variety of the Idria ore seems very complex in composition,
according to the following analysis of Klaproth:--Mercury, 81·8;
sulphur, 13·75; carbon, 2·3; silica, 0·65; alumina, 0·55; oxide of iron,
0·20; copper, 0·02; water, 0·73; in 100 parts. M. Beurard mentions
another variety from the Palatinate, which yields a large quantity of
bitumen by distillation; and it was present in all the specimens of
these ores analyzed by me for the German Mines Company. At Idria and
Almaden the sulphurets are extremely rich in mercury.
4. _Muriated mercury_, or the _Chloride of mercury_, commonly called
Horn mercury. This ore occurs in very small crystals of a pearl-gray or
greenish-gray colour, or in small nipples which stud, like crystals, the
cavities, fissures, or geodes among the ferruginous gangues of the other
ores of mercury. It is brittle, and entirely volatile at the blowpipe,
characters which distinguish it from horn silver.
The geological position of the mercurial ores, in all parts of the
world, is in the strata which commence the series of secondary
formations. Sometimes they are found in the red sandstone above the
coal, as at Menildot, in the old dutchy of Deux-Ponts, at Durasno in
Mexico, at Cuença in New Granada, at Cerros de Gauzan and Upar in Peru;
in the subordinate porphyries, as at Deux-Ponts, San Juan de la Chica in
Peru, and at Cerro-del-Fraile, near the town of San-Felipe, they occur
also among the strata below, or subordinate to the calcareous formation,
called _zechstein_, in Germany, or among the accompanying bituminous
schists, as at Idria in Carniola; and, lastly, they form masses in the
zechstein itself. Thus, it appears that the mercurial deposits are
confined within very narrow geological limits, between the calcareous
beds of zechstein, and the red sandstone. They occur at times in
carbonaceous nodules, derived from the decomposition of mosses of
various kinds; and the whole mercurial deposit is occasionally covered
with beds of charcoal, as at Durasno.
They are even sometimes accompanied with the remains of organic bodies,
such as casts of fishes, fossil shells, silicified wood, and true coal.
The last fact has been observed at Potzberg, in the works of
Drey-Koenigszug, by M. Brongniart. These sandstones, bituminous schists,
and indurated clays, contain mercury both in the state of sulphuret and
in the native form. They are more or less penetrated with the ore,
forming sometimes numerous beds of very great thickness; while, in the
more antient or the primitive formations, these ores exist only in very
small quantity associated with tin. Mercury is, generally speaking, a
metal sparingly distributed in nature, and its mines are very rare.
The great exploitations of Idria in Friuli, in the county of Goritz,
were discovered in 1497, and the principal ore mined there is the
bituminous sulphuret. The workings of this mine have been pushed to the
depth of 280 yards. The product in quicksilver might easily amount
annually to 6000 metric quintals = 600 tons British; but, in order to
uphold the price of the metal, the Austrian government has restricted
the production to 150 tons. The memorable fire of 1803 was most
disastrous to these mines. It was extinguished only by drowning all the
underground workings. The sublimed mercury in this catastrophe
occasioned diseases and nervous tremblings to more than 900 persons in
the neighbourhood.
Pliny has recorded two interesting facts: 1. that the Greeks imported
red cinnabar from Almaden 700 years before the Christian era; and 2.
that Rome, in his time, annually received 700,000 pounds from the same
mines. Since 1827, they have produced 22,000 cwts. of mercury every
year, with a corps of 700 miners and 200 smelters; and, indeed, the
veins are so extremely rich, that though they have been worked pretty
constantly during so many centuries, the mines have hardly reached the
depth of 330 yards, or something less than 1000 feet. The lode actually
under exploration is from 14 to 16 yards thick, and it becomes thicker
still at the crossing of the veins. The totality of the ore is
extracted. It yields in their smelting works only 10 per cent. upon an
average, but there is no doubt, from the analysis of the ores, that
nearly one half of the quicksilver is lost, and dispersed in the air, to
the great injury of the workmen’s health, in consequence of the
barbarous apparatus of aludels employed in its sublimation; an apparatus
which has remained without any material change for the better since the
days of the Moorish dominion in Spain. M. Le Play, the eminent
_Ingenieur des Mines_, who published, in a recent volume of the Annales
des Mines, his _Itinéraire_ to Almaden, says, that the mercurial
contents of the ores are _notablement plus elevées_ than the product.
These veins extend all the way from the town of Chillon to Almadenejos.
Upon the borders of the streamlet Balde Azogues, a black slate is also
mined which is abundantly impregnated with metallic mercury. The ores
are treated in 13 double furnaces, which I shall presently describe. “Le
mercure,” says M. Le Play, “a sur la santé des ouvriers la plus funeste
influence, et l’on ne peut se défendre d’un sentiment pénible en voyant
l’empressement avec lequel des jeunes gens, pleins de force et de santé,
se disputent la faveur d’aller chercher dans les mines, des maladies
cruelles, et souvent une mort prématurée. La population des mineurs
d’Almaden méritent le plus haut interêt.” These victims of a deplorable
mismanagement are described as being a laborious, simple-minded,
virtuous race of beings, who are thus condemned to breathe an atmosphere
impregnated far and near with the fumes of a volatile poison, which the
lessons of science, as I shall presently demonstrate, might readily
repress, with the effect of not only protecting the health of the
population, but of vastly augmenting the revenues of the state.
These celebrated mines, near to which lie those of _Las Cuebas_ and of
_Almadenejos_, were known to the Romans. After having been the property
of the religious knights of _Calatrava_, who had assisted in expelling
the Moors, they were farmed off to the celebrated _Fugger_ merchants of
Augsbourg; and afterwards explored on account of the government, from
the date of 1645 till the present time. Their produce was, till very
lately, entirely appropriated to the treatment of the gold and silver
ores of the new world.
The mines of the _Palatinate_, situated on the left bank of the Rhine,
though they do not approach in richness and importance to those of Idria
and Almaden, merit, however, all the attention of the government that
farms them out. They are numerous, and varied in geological position.
Those of Drey-Koenigszug, at Potzberg, near Kussel, deserve particular
notice. The workings have reached a depth of more than 220 yards; the
ore being a sandstone strongly impregnated with sulphuret of mercury.
The produce of these mines is estimated at about 30 tons per annum.
There are also in Hungary, Bohemia, and several other parts of Germany,
some inconsiderable exploitations of mercury, the total produce of which
is valued at about 30 or 40 tons on an average of several years.
The mines of Guancavelica, in Peru, are the more interesting, as their
products are directly employed in treating the ores of gold and silver,
which abound in that portion of America. These quicksilver mines,
explored since 1570, produced, up to 1800, 53,700 tons of that metal;
but the actual produce of the explorations of these countries was,
according to Helms, about the beginning of this century, from 170 to 180
tons per annum.
In 1782 recourse was had by the South American miners to the mercury
extracted in the province of Yun-nan, in China.
The metallurgic treatment of the quicksilver ores is tolerably simple.
In general, when the sulphuret of mercury, the most common ore, has been
pulverized, and sometimes washed, it is introduced into retorts of cast
iron, sheet iron, or even stoneware, in mixture with an equal weight of
quicklime. These retorts are arranged in various ways.
Prior to the 17th century, the method called _per descensum_ was the
only one in use for distilling mercury; and it was effected by means of
two earthen pots adjusted over each other. The upper pot, filled with
ore, and closed at the top, was covered over with burning fuel; and the
mercurial vapours expelled by the heat, passed down through small holes
in the bottom of the pot, to be condensed in another vessel placed
below. However convenient this apparatus might be, on account of the
facility of transporting it, wherever the ore was found, its
inefficiency and the losses it occasioned were eventually recognized.
Hence, before 1635, some smelting works of the Palatinate had given up
the method _per descensum_, which was, however, still retained in Idria;
and they substituted for it the furnaces called _galleries_. At first
earthenware retorts were employed in these furnaces; but they were soon
succeeded by iron retorts. In the Palatinate this mode of operating is
still in use. At Idria, in the year 1750, a great distillatory apparatus
was established for the treatment of the mercurial ores, in imitation of
those which previously existed at Almaden, in Spain, and called
_aludel-furnaces_. But, since 1794, these aludels have been suppressed,
and new distillatory apparatus have been constructed at Idria,
remarkable only for their magnitude; exceeding, in this respect, every
other metallurgic erection.
There exist, therefore, three kinds of apparatus for the distillation of
mercury: 1. the furnace called a _gallery_; 2. the furnace with
_aludels_; and 3. the _large apparatus_ of Idria. I shall describe each
of these briefly, in succession.
[Illustration: 656 657 658]
1. _Furnace called Gallery of the Palatinate._--The construction of this
furnace is disposed so as to contain four ranges, _a a´_, _b b´_, of
large retorts, styled cucurbits, of cast iron, in which the ore of
mercury is subjected to distillation. This arrangement is shewn in
_fig._ 656., which presents a vertical section in the line _a b_ of the
ground plan, _fig._ 657. In the ground plan, the roof _e e´_ of the
furnace (_fig._ 656.) is supposed to be lifted off, in order to shew the
disposition of the four ranges of cucurbits upon the grate _c f_,
_figs._ 656, 657., which receives the pit-coal employed as fuel. Under
this grate extends an ash-pit _d_. _Fig._ 658., which exhibits an
elevation of the furnace, points out this ash-pit, as well as one of the
two doors _c_, by which the fuel is thrown upon the grate _c f_.
Openings _e e_, (_fig._ 656.) are left over the top arch of the furnace,
whereby the draught of air may receive a suitable direction. The grate
of the fire-place extends over the whole length of the furnace, _fig._
657., from the door _c_ to the door _f_, situated at the opposite
extremity. The furnace called _gallery_ includes commonly 30 cucurbits,
and in some establishments even 52. Into each are introduced from 56 to
70 pounds of ore, and 15 to 18 pounds of quicklime, a mixture which
fills no more than two-thirds of the cucurbit; to the neck a stoneware
receiver is adapted, containing water to half its height. The fire, at
first moderate, is eventually pushed till the cucurbits are red hot. The
operation being concluded, the contents of the receivers are poured out
into a wooden bowl placed upon a plank above a bucket; the quicksilver
falls to the bottom of the bowl, and the water draws over the _black
mercury_, for so the substance that coats the inside of the receivers is
called. This is considered to be a mixture of sulphuret and oxide of
mercury. The _black mercury_, taken out of the tub and dried, is
distilled anew with excess of lime; after which the residuum in the
retorts is thrown away, as useless.
[Illustration: 659 660]
_Aludel furnaces of Almaden._--_Figs._ 659. and 660. represent the great
furnaces with aludels in use at Almaden, and anciently in Idria; for
between the two establishments there was in fact little difference
before the year 1794. _Figs._ 659. and 662. present two vertical
sections; _figs._ 660. and 661. are two plans of two similar furnaces,
conjoined in one body of brickwork. In the four figures the following
objects are to be remarked; a door _a_, by which the wood is introduced
into the fire-place _b_. This is perforated with holes for the passage
of air; the ash-pit _c_, is seen beneath. An upper chamber _d_, contains
the mercurial ores distributed upon open arches, which form the
perforated sole of this chamber. Immediately over these arches, there
are piled up in a dome form, large blocks of a limestone, very poor in
quicksilver ore; above these are laid blocks of a smaller size, then
ores of rather inferior quality, and stamped ores mixed with richer
minerals. Lastly, the whole is covered up with soft bricks, formed of
clay kneaded with _schlich_, and with small pieces of sulphuret of
mercury. Six ranges of aludels or stoneware tubes, _f f_, of a pear
shape, luted together with clay, are mounted in front of each of the two
furnaces, on a double sloping terrace, having in its lowest middle line
two gutters _t v_, a little inclined towards the intermediate wall _m_.
In each range the aludel placed at the line _t m v_ of _fig._ 660., that
is to say at the lowest point, _g_, _figs._ 659. 662., is pierced with a
hole. Thereby the mercury which had been volatilized in _d_, if it be
already condensed by the cooling in the series of aludels _f g_, may
pass into the corresponding gutter, next into the hole _m_, _fig._ 660.,
and after that into the wooden pipes _h h´_, _fig._ 659., which conduct
it across the masonry of the terrace into cisterns filled with water;
see _q_, _fig._ 661., which is the plan of _fig._ 662.
[Illustration: 661 662]
The portion of mercury not condensed in the range of aludels, _f g_,
which is the most considerable, goes in the state of vapour, into a
chamber _k_; but in passing under a partition _l l_, a certain portion
is deposited in a cistern _i_, filled with water. The greater part of
the vapours diffused in the chamber _k´_ is thereby condensed, and the
mercury falls down upon the two inclined planes which form its bottom.
What may still exist as vapour passes into an upper chamber _k´_, by a
small chimney _n_. On one of the sides of this chamber there is a
shutter which may be opened at pleasure from below upwards, and beneath
this shutter, there is a gutter into which a notable quantity of mercury
collects. Much of it is also found condensed in the aludels. These facts
prove that this process has inconveniences, which have been tried to be
remedied by the more extensive but rather unchemical grand apparatus of
Idria.
Details of the aludel apparatus: 25 are set in each of the 12 ranges,
seen in _fig._ 661. constituting 300 pear-shaped stoneware vessels, open
at both ends, being merely thrust into one another, and luted with loam.
What a multitude of joints, of which a great many must be continually
giving way by the shrinkage of the luting, whereby the mercurial fumes
will escape with great loss of product, to poison the air!
_a_, is the door of the fire-place; _c_, the perforated arches upon
which the ore is piled in the chamber _e_, through the door _d_, and an
orifice at top; the latter being closed during the distillation; _f f_
are vents for conducting the mercurial vapours into two chambers _i_,
separated by a triangular body of masonry _m n_; _h_ is the smoke
chimney of the fire-place; _o o_, are the ranges of aludels, in
connection with the chamber _i_, which are laid slantingly towards the
gutter _q_, upon the double inclined plane terrace, and terminate in the
chamber _h q_; this being surmounted by two chimneys _t_. The mercury is
collected in these aludels and in the basins at _q_ and _p_, _fig._ 661.
_r_ is a thin stone partition set up between the two principal walls of
each of the furnaces. _v_ is the stair of the aludel terrace, leading to
the platform which surmounts the furnace; _z_ is a gutter for conducting
away the rains which may fall upon the buildings.
_Great apparatus of Idria._--Before entering into details of this
laboratory, it will not be useless to recapitulate the metallurgic
classification of the ores treated in it. 1. The ores in large blocks,
fragments, or shivers, whose size varies from a cubic foot to that of a
nut. 2. The smaller ores, from the size of a nut to that of grains of
dust.
The first class of _large_ ores comprises three subdivisions, namely;
_a_, blocks of metalliferous rocks, which is the most abundant and the
poorest species of ore, affording only one _per cent._ of mercury; _b_,
the massive sulphuret of mercury, the richest and rarest ore, yielding
80 _per cent._ when it is picked; _c_, the fragments or splinters
proceeding from the breaking and sorting, and which vary in value, from
1 to 40 _per cent._
The second class of small ores comprises: _d_, the fragments or shivers
extracted from the mine in the state of little pieces, affording from 10
to 12 _per cent._; _e_, the kernels of ore, separated on the sieve,
yielding 32 _per cent._; _f_, the sands and paste called _schlich_,
obtained in the treatment of the poorest ores, by means of the stamps
and washing tables; 100 parts of this _schlich_ give at least 8 of
quicksilver.
The general aspect of the apparatus is indicated by _figs._ 663, 664.
and 665. _Fig._ 665. represents the exterior, but only one half, which
is enough, as it resembles exactly the other, which is not shown. In
these three figures the following objects may be distinguished; _figs._
663, 664., _a_, door of the fire-place; _b_, the furnace in which
beech-wood is burned mixed with a little fir-wood; _c_, door of the
ash-pit, extended beneath; _d_, a space in which the ores are deposited
upon the seven arches, 1. to 7., as indicated in _figs._ 663. and 666.;
_e e_, brick tunnels, by which the smoke of the fuel and the vapours of
mercury pass, on the one side, into successive chambers _f k_.
[Illustration: 663 664]
_f g h i j k l_ are passages which permit the circulation of the vapours
from the furnace _a b c d_, to the chimneys _l l_. _Figs._ 663. and 664.
exhibit clearly the distribution of these openings on each side of the
same furnace, and in each half of the apparatus, which is double, as
_fig._ 664. shows; the spaces without letters being in every respect
similar to the spaces mentioned below. _Fig._ 664. is double the scale
of _fig._ 663.
[Illustration: 665]
_m m´_, _fig._ 664., are basins of reception, distributed before the
doors of each of the chambers _f k f´ k´_. The condensed mercury which
flows out of the chambers is conveyed thither. _n n´_ is a trench into
which the mercury, after being lifted into the basins _m_, is poured, so
that it may run towards a common chamber _o_, in the sloping direction
indicated by the arrows. _o_ leads to the chamber where the mercury is
received into a porphyry trough; out of which it is laded and packed up
in portions of 50 or 100 lbs. in sheep-skins prepared with alum. _p p´_,
_fig._ 663., are vaulted arches, through which a circulation may go on
round the furnace _a b c d_, on the ground level, _q q´_ are the vaults
of the upper stories. _r r´_, _fig._ 665., vaults which permit access to
the tunnels _e´ e´´_, _fig._ 663.
[Illustration: 666]
_s s´_ and _t t´_, _fig._ 665., are the doors of the chambers, _f k_ and
_f´ k´_. These openings are shut during the distillation by wooden doors
faced with iron, and luted with a mortar of clay and lime. _u u´_ is the
door of the vaults 1. to 7. of the furnace represented in _fig._ 663.
These openings are hermetically shut, like the preceding. _v v´_, _fig._
663., are superior openings of the chambers, closed during the operation
by luted plugs; they are opened afterwards to facilitate the cooling of
the apparatus, and to collect the mercurial soot. _x y z_, _fig._ 666.,
are floors which correspond to the doors _u u´_ of the vaults 1. to 7.,
_fig._ 665. These floors are reached by stairs set up in the different
parts of the building, which contains the whole apparatus.
On the lower arches the largest blocks of metalliferous rock are laid;
over these the less bulky fragments are arranged, which are covered with
the shivers and pieces of less dimension. On the middle vaults, the
small ore is placed, distributed into cylindrical pipkins of
earthenware, of 10 inches diameter and 5 inches depth. The upper vaults
receive likewise pipkins filled with the sands and pastes called
_schlich_.
In 3 hours, by the labour of 40 men, the two double sets of apparatus
are charged, and all the apertures are closed. A quick fire of
beech-wood is then kindled; and when the whole mass has become
sufficiently heated, the sulphuret of mercury begins to vapourize;
coming into contact with the portion of oxygen which had not been
carbonated, by combustion, its sulphur burns into sulphurous acid, while
the mercury becomes free, passes with the other vapours into the
chambers for condensing it, and precipitates in the liquid form at a
greater or less distance from the fire-place. The walls of the chambers
and the floors, with which their lower portion is covered, are soon
coated over with a black mercurial soot, which, being treated anew,
furnishes 50 _per cent._ of mercury. The distillation lasts from 10 to
12 hours; during which time the whole furnace is kept at a cherry-red
heat. A complete charge for the two double apparatus, consists of from
1000 to 1300 quintals of ore, which produce from 80 to 90 quintals of
running mercury. The furnace takes from 5 or 6 days to cool, according
to the state of the weather; and if to that period be added the time
requisite for withdrawing the residuums, and attending to such repairs
as the furnace may need, it is obvious that only one distillation can be
performed in the course of a week.
In the works of Idria, in 1812, 56,686 quintals and a half of
quicksilver ores were distilled, after undergoing a very careful
mechanical preparation. They afforded 4832 quintals of running mercury;
a quantity corresponding to about 8-1/2 _per cent._ of the ore. These
smelting works are about 180 feet long and 30 feet high.
Upon the preceding three systems of smelting mercurial ores, I shall now
make some observations.
It has been long well known, that quicksilver may be most readily
extracted from cinnabar, by heating it in contact with quicklime. The
sulphur of the cinnabar combines, by virtue of a superior affinity with
the lime, to the exclusion of the quicksilver, to form sulphurets of
lime and calcium, both of which being fixed _hepars_, remain in the
retort while the mercury is volatilized by the heat. In a few places,
hammerschlag, or the iron cinder, driven off from the blooms by the
tilting hammer, has been used instead of lime in the reduction of this
mercurial ore, whereby sulphurous acid and sulphuret of iron are formed.
The annual production of the Bavarian Rhine provinces has been estimated
at from 400 to 550 quintals; that of Almaden, in the year 1827, was
22,000 quintals; and of Idria, at present, is not more than 1500
quintals.
All the plans hitherto prescribed for distilling the ore along with
quicklime, are remarkably rude. In that practised at Landsberg by
Obermoschel, there is a great waste of labour, in charging the numerous
small cucurbits; there is a great waste of fuel in the mode of heating
them; a great waste of mercury by the imperfect luting of the retorts to
the receivers, as well as the imperfect condensation of the mercurial
vapours; and probably a considerable loss by pilfering.
The modes practised at Almaden and Idria are, in the greatest degree,
barbarous; the ores being heated upon open arches, and the vapours
attempted to be condensed by enclosing them within brick or stone and
mortar walls, which can never be rendered either sufficiently tight or
cool.
To obviate all these inconveniences and sources of loss, the proper
chemical arrangements suited to the present improved state of the arts
ought to be adopted, by which labour, fuel, and mercury, might all be
economized to the utmost extent. The only apparatus fit to be employed
is a series of cast-iron cylinder retorts, somewhat like those employed
in the coal gas works, but with peculiarities suited to the condensation
of the mercurial vapours. Into each of these retorts, supposed to be at
least one foot square in area, and 7 feet long, 6 or 7 cwt. of a mixture
of the ground ore with the quicklime, may be easily introduced, from a
measured heap, by means of a shovel. The specific gravity of the
cinnabar being more than 6 times that of water, a cubic foot of it will
weigh more than 3-1/2 cwt.; but supposing the mixture of it with
quicklime (when the ore does not contain the calcareous matter itself)
to be only thrice the density of water, then four cubic feet might be
put into each of the above retorts, and still leave 1-1/2 cubic feet of
empty space for the expansion of volume which may take place in the
decomposition. The ore should certainly be ground to a moderately fine
powder, by stamps, iron cylinders, or an edge wheel, so that when mixed
with quicklime, the cinnabar may be brought into intimate contact with
its decomposer, otherwise much of it will be dissipated unproductively
in fumes, for it is extremely volatile.
_Figs._ 667, 668, 669. represent a cheap and powerful apparatus which I
contrived at the request of the German Mines Company of London, and
which is now mounted at Landsberg, near Obermoschel, in the Bavarian
Rhein-Kreis.
[Illustration: 667]
_Fig._ 667. is a section parallel to the front elevation of three arched
benches of retorts, of the size above specified. Each bench contains 3
retorts, of the form represented by _a a a_. I, is the single fire-place
or furnace, capable of giving adequate ignition by coal or wood, to the
three retorts. The retorts were built up in an excellent manner, by an
English mason perfectly acquainted with the best modes of erecting
coal-gas retorts, who was sent over on purpose. The path of the flame
and smoke is precisely similar to that represented in _fig._ 483, page
549, whereby the uppermost retort is immersed in a bath of uniformly
ignited air, while the currents reverberated from the top, play round
the two undermost retorts, in their way to the vent-flues beneath them.
The bottom of the uppermost retort is protected from the direct impulse
of the flame by fire-tiles. The dotted lines K K, show the paths of the
chimneys which rise at the back ends of the retorts.
[Illustration: 668 669]
In the section, _fig._ 668., _a_ is the body of the retort; its mouth at
the right hand end is shut, as usual, by a luted iron lid, secured with
a cross-bar and screw-bolts; its other end is prolonged by a sloping
pipe of cast iron, 4 inches in diameter, furnished with a nozzle hole at
L, closed with a screw plug. Through this hole a wire rammer may be
introduced, to ascertain that the tube is pervious, and to cleanse it
from the mercurial soot, when thought necessary. _c_, is a cross section
of the main condenser, shown in a longitudinal section at C C, _fig._
669. This pipe is 18 inches in diameter, and about 20 feet long. At _a
a_, &c., the back ends of the retorts are seen, with the slanting tubes
_b b_, &c., descending through orifices in the upper surface of the
condenser pipe, and dipping their ends just below the water-line _h i_.
_g_, is the cap of a water valve, which removes all risk from sudden
expansion or condensation. The condenser is placed within a rectangular
trough, made either of wood or stone, through which a sufficient stream
of water passes to keep it perfectly cool, and repress every trace of
mercurial vapour, and it is laid with a slight inclination from _i_ to
_h_, so that the condensed quicksilver may spontaneously flow along its
bottom, and pass through the vertical tube D into the locked up iron
chest, or magazine _e_. This tube D is from the beginning closed at
bottom, by immersion in a shallow iron cup, always filled with mercury.
_k_ is a graduated gauge rod, to indicate the progressive accumulation
of quicksilver in the chest, without being under the necessity of
unlocking it.
This air-tight apparatus was erected about a year ago, and has been
found to act perfectly well; I regret, however, that my professional
engagements at home have not hitherto permitted me to conduct its
operations personally for some days. The average samples of cinnabar ore
from Obermoschel are ten times poorer than those of Almaden. Were such
an apparatus as the above, with some slight modifications which have
lately occurred to me, mounted for the Spanish mines, I am confident
that their produce in quicksilver might be nearly doubled, with a vast
economy of fuel, labour, and human life. The whole cost of the 9 large
retorts, with their condensing apparatus, iron magazine, &c., was very
little more than _two hundred pounds_! As the retorts are kept in a
state of nearly uniform ignition, like those of the gas works, neither
they, nor the furnaces are liable to be injured in their joints by the
alternate contractions and expansions, which they would inevitably
suffer if allowed to cool; and being always ready heated to the proper
pitch for decomposing the mercurial ores, they are capable of working
off a charge, under skilful management, in the course of 3 hours. Thus,
in 24 hours, with a relay of labourers, 8 charges of at least 5 cwts. of
ore each, might be smelted = 2 tons, with 3 retorts, and 6 tons with 9
retorts; with a daily product from the rich ores of Almaden, or even
Idria, of from 12 cwts. to 20 cwts. Instead of 3 benches of 3 retorts
each, I would recommend 15 benches, containing 45 retorts, to be erected
for either the Almaden or Idria mines; which, while they would smelt all
their ores, could be got for a sum not much exceeding 1000_l._, an
outlay which they would reimburse within a month or two.
Quicksilver is a substance of paramount value to science. Its great
density and its regular rate of expansion and contraction by increase
and diminution of temperature, give it the preference over all liquids
for filling barometric and thermometric tubes. In chemistry it furnishes
the only means of collecting and manipulating, in the pneumatic trough,
such gaseous bodies as are condensable over water. To its aid, in this
respect, the modern advancement of chemical discovery is pre-eminently
due.
This metal alloyed with tin-foil forms the reflecting surface of looking
glasses, and by its ready solution of gold or silver, and subsequent
dissipation by a moderate heat, it becomes the great instrument of the
arts of gilding and silvering copper and brass. The same property makes
it so available in extracting these precious metals from their ores. The
anatomist applies it elegantly, to distend and display the minuter
vessels of the lymphatic system, and secretory systems, by injecting it
with a syringe through all their convolutions. It is the basis of many
very powerful medicines, at present probably too indiscriminately used,
to the great detriment of English society; for it is far more sparingly
prescribed by practitioners upon the continent of Europe, not otherwise
superior in skill or science to those of Great Britain.
The nitrate of mercury is employed for the _secrétage_ of rabbit and
hare-skins, that is, for communicating to the fur of these and other
quadrupeds the faculty of felting, which they do not naturally possess.
With this view the solution of that salt is applied to them lightly in
one direction with a sponge. A compound amalgam of zinc and tin is
probably the best exciter which can be applied to the cushions of
electrical machines. Mercury imported for home consumption in 1836,
286,808 lbs.; in 1837, 314,036 lbs.
The only mercurial compounds which are extensively used in the arts, are
fictitious cinnabar or VERMILLION, and corrosive sublimate.
MERCURY, BICHLORIDE OF; _Corrosive sublimate_; (_Deutochlorure de
mercure_, Fr.; _Aetzendes quecksilber sublimat_, Germ.) is made by
subliming a mixture of equal parts of persulphate of mercury, prepared
as above described, and sea-salt, in a stone-ware cucurbit. The
sublimate rises in vapour, and encrusts the globular glass capital with
a white mass of small prismatic needles. Its specific gravity is 5·14.
Its taste is acrid, stypto-metallic, and exceedingly unpleasant. It is
soluble in 20 parts of water, at the ordinary temperature, and in its
own weight of boiling water. It dissolves in 2-1/2 times its weight of
cold alcohol. It is a very deadly poison. Raw white of egg swallowed in
profusion, is the best antidote. A solution of corrosive sublimate has
been long employed for preserving soft anatomical preparations. By this
means the corpse of Colonel Morland was embalmed, in order to be brought
from the seat of war to Paris. His features remained unaltered, only his
skin was brown, and his body was so hard as to sound like a piece of
wood when struck with a hammer.
In the valuable work upon the dry rot, published by Mr. Knowles,
secretary of the committee of inspectors of the navy, in 1821, corrosive
sublimate is enumerated among the chemical substances which had been
prescribed for preventing the dry rot in timber; and it is well known
that Sir H. Davy had, several years before that date, used and
recommended to the Admiralty and Navy Board, corrosive sublimate as an
anti-dry rot application. It has been since extensively employed by a
joint-stock company for the same purpose, under the title of Kyan’s
patent.
MERCURY, PROTOCHLORIDE OF; _Calomel_; (_Protochlorure de mercure_, Fr.,
_Versüsstes quecksilber_, Germ.) This compound, so much used and abused
by medical practitioners, is commonly prepared by triturating four parts
of corrosive sublimate along with three parts of running quicksilver in
a marble mortar, till the metallic globules entirely disappear, with the
production of a black powder, which is to be put into a glass balloon,
and exposed to a subliming heat in a sand bath. The calomel, which rises
in vapour, and attaches itself in a crystalline crust to the upper
hemisphere of the balloon, is to be detached, reduced to a fine powder,
or levigated and elutriated. 200 lbs. of mercury yield 236 of calomel
and 272 of corrosive sublimate.
The following more economical process is that adopted at the
Apothecaries’ Hall, London. 140 pounds of concentrated sulphuric acid
are boiled in a cast iron pot upon 100 pounds of mercury, till a dry
persulphate is obtained. Of this salt, 124 pounds are triturated with 81
pounds of mercury, till the globules disappear, and till a protosulphate
be formed. This is to be intimately mixed with 68 pounds of sea-salt,
and the mixture, being put into a large stone-ware cucurbit, is to be
submitted to a subliming heat. See CALOMEL.
From 190 to 200 pounds of calomel rise in a crystalline cake, as in the
former process, into the capital; while sulphate of soda remains at the
bottom of the alembic. The calomel must be ground to an impalpable
powder, and elutriated. The vapours, instead of being condensed into a
cake within the top of the globe or in a capital, may be allowed to
diffuse themselves into a close vessel, containing water in a state of
ebullition, whereby the calomel is obtained at once in the form of a
washed impalpable powder. Calomel is tasteless and insoluble in water.
Its specific gravity is 7·176.
For the compound of mercury with fulminic acid, see FULMINATE.
_Periodide of mercury_ is a bright but fugitive red pigment. It is
easily prepared by dropping a solution of iodide of potassium into a
solution of corrosive sublimate, as long as any precipitation takes
place, decanting off the supernatant muriate of potash, washing and
drying the precipitate.
METALLURGY (_Erzkunde_, Germ.) is the art of extracting metals from
their ores. This art, which supplies industry with the instruments most
essential to its wants, is alike dependent upon the sciences of
chemistry and mechanics; upon the former, as directing the smelting
processes, best adapted to disentangle each metal from its mineralizer;
upon the latter, as furnishing the means of grinding the ores, and
separating the light stony parts from the rich metallic matter.
Notwithstanding the striking analogy which exists between common
chemical and metallurgic operations, since both are employed to insulate
certain bodies from others, there are essential differences which should
be carefully noted. In the first place, the quantity of materials being
always very great in metallurgy, requires corresponding adaptations of
apparatus, and often produces peculiar phenomena; in the second place,
the agents to be employed for treating great masses, must be selected
with a view to economy, as well as to chemical action. In analytical
chemistry, the main object being exactness of result, and purity of
product, little attention is bestowed upon the value of the reagents, on
account of the small quantity required for any particular process. But
in smelting metals upon the great scale, profit being the sole object,
cheap materials and easy operations alone are admissible.
The metallic ores as presented by nature, are almost always mixed with a
considerable number of foreign substances; and could not therefore be
advantageously submitted to metallurgic operations, till they are
purified and concentrated to a certain degree by various methods.