f g h i j k l

are pa ages 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. IMG:4147767755307473660_illo0808a.png:Apparatus of Idria 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 acce to the tunnels e′ e′ ′ , fig. 663. IMG:4147767755307473660_illo0808b.png:Apparatus of Idria 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 le bulky fragments are arranged, which are covered with the shivers and pieces of le 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 ma 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, pa es with the other vapours into the chambers for condensing it, and precipitates in the liquid form at a greater or le 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 Lands berg 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 lo 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 lo , 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 di ipated 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 Lands berg, near Obermoschel, in the Bavarian Rhein-Kreis. IMG:4147767755307473660_illo0809.png:Lands berg apparatus 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. IMG:4147767755307473660_illo0810.png:Lands berg apparatus 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 cro -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 nece ary. c , is a cro 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 , ., the back ends of the retorts are seen, with the slanting tubes b b , ., 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 pa es to keep it perfectly cool, and repre 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 pa 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 progre ive accumulation of quicksilver in the chest, without being under the nece ity 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 profe ional 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, ., 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 gla es, and by its ready solution of gold or silver, and subsequent di ipation by a moderate heat, it becomes the great instrument of the arts of gilding and silvering copper and bra . 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 ve els 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 po e . 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.