Refining of lead to extract its silver

—This operation, which the lead of Derby shire cannot be submitted to with advantage, is performed in a certain number of the smelting-houses at Alston-moor, and always upon leads reduced in the Scotch furnace. The cupel furnace above described, must be slowly heated, in order to dry the cupel of the moisture in it. When it has been thus slowly brought to the verge of a red heat, it is almost completely filled with lead previously melted in an iron pot. The cupel may be charged with about 5 cwt. At the temperature at which the lead is introduced, it is immediately covered with a gray pellicle of oxide; but when the heat of the furnace has been progre ively raised to the proper pitch, it becomes whitish-red, and has its surface covered over with litharge. Now is the time to set in action the blowing-machine, the blast of which, impelled in the direction of the great axis of the cupel, drives the litharge towards the breast of the cupel, and makes it flow out by the gateway prepared for it, through which it falls upon a cast-iron plate, on a level with the floor of the apartment, and is dispersed into tears. It is carried in this state to the furnace of reduction, and revived. As by the effect of the continual oxidization which it undergoes, the surface of the metal nece arily falls below the level of the gateway of the litharge, melted lead must be added anew by ladling it into the furnace from the iron boiler, as occasion may require. The operation is carried on in this manner till 84 cwt. or 4 Newcastle fodders of lead have been introduced, which takes from 16 to 18 hours, if the tuyère has been properly set. The whole quantity of silver which this ma of lead contains, is left in combination with about 1 cwt. of lead, which, under the name of rich lead, is taken out of the cupel. When a sufficient number of these pieces of rich lead have been procured, so that by their respective quality, as determined by a aying, they contain in whole from 1000 to 2000 ounces of silver, they are re-melted to extract their silver, in the same furnace, but in a cupel which differs from the former in having at its bottom a depre ion capable of receiving at the end of the proce the cake of silver. In this case a portion of the bottom remains uncovered, on which the scoriæ may be pushed aside with a little rake, from the edges of the silver. The experiments of MM. Lucas and Gay Lu ac have proved that fine silver, exposed to the air in a state of fusion, absorbs oxygen gas, and gives it out again in the act of consolidation. The quantity of oxygen thus absorbed may amount to twenty-two times the volume of the silver. The following phenomena are observed when the ma of metal is considerable; for example, from 40 to 50 pounds. The solidification commences at the edges, and advances towards the centre. The liquid silver, at the moment of its pa age to the solid state, experiences a slight agitation, and then becomes motionle . The surface, after remaining thus tranquil for a little, gets all at once irregularly perturbed, fi ures appear in one or several lines, from which flow, in different directions, streams of very fluid silver, which increase the original agitation. The first stage does not yet clearly manifest the presence of gas, and seems to arise from some intestine motion of the particles in their tendency to group, on entering upon the proce of crystallization, and thus causing the rupture of the envelop or external crust, and the ejection of some liquid portions. After remaining some time tranquil, the metal presents a fresh appearance, precisely analogous to volcanic phenomena. As the crystallization continues, the oxygen gas is given out with violence at one or more points, carrying with it melted silver from the interior of the surface, producing a series of cones, generally surmounted by a small crater, vomiting out streams of the metal, which may be seen boiling violently within them. These cones gradually increase in height by the accumulation of metal thrown up, and that which becomes consolidated on their sloping sides. The thin crust of metal on which they rest, consequently experiences violent impulses, being alternately raised and depre ed by such violent agitation, that were it not for the tenacity and elasticity of the metal, there would evidently arise dislocation, fi ures, and other analogous accidents. At length several of the craters permanently close, while others continue to allow the gas a pa age. The more difficult this is, the more the craters become elevated, and the more their funnels contract by the adhesion or coagulation of a portion of the metal. The projection of globules of silver now becomes more violent; the latter being carried to great distances, even beyond the furnace, and accompanied by a series of explosions, repeated at short intervals. It is generally the last of these little volcanoes that attains the greatest altitude, and exhibits the foregoing phenomena with the greatest energy. It is, moreover, observable, that these cones do not all arise at the same time, some having spent their force, when others commence forming at other points. Some reach the height of an inch, forming bases of two or three inches in diameter. The time occupied by this exhibition is at least from half to three quarters of an hour. During the formation of these cones, by the evolution of gas, portions of silver are shot forth, which a ume, on induration, a form somewhat cylindrical, and often very fantastic, notwithstanding the incompatibility which appears to exist between the fluidity of the silver and these elongated figures. Their appearance is momentary, and without any symptoms of gas, although it is impo ible to decide whether they may not arise from its influence; they seem, in fact, to resemble the phenomena of the first volcanic period. Till very recently the only operations employed for separating silver from lead in the English smelting-works, were the following :— 1. Cupellation, in which the lead was converted into a vitreous oxide, which was floated off from the surface of the silver. 2. Reduction of that oxide, commonly called litharge. 3. Smelting the bottoms of the cupels, to extract the lead which had soaked into them, in a gla y state. Cupellation and its two complementary operations were, in many respects, objectionable proce es; from the injurious effects of the lead vapours upon the health of the workmen; from the very considerable lo of metallic lead, amounting to 7 per cent. at least; and, lastly, from the immense consumption of fuel, as well as from the vast amount of manual labour incurred in such complicated operations. Hence, unle the lead were tolerably rich in silver, it would not bear the expense of cupellation. The patent proce lately introduced by Mr. Pattinson, of Newcastle, is not at all prejudicial to the health of workmen; it does not occasion more than 2 per cent. of lo of lead, and in other respects it is so economical, that it is now profitably applied in North umber land to alloys too poor in silver to be treated by cupellation. This proce is founded upon the following phenomena. After melting completely an alloy of lead and silver, if we allow it to cool very slowly, continually stirring it meanwhile with a rake, we shall observe at a certain period a continually increasing number of imperfect little crystals, which may be taken out with a drainer, exactly as we may remove the crystals of sea salt deposited during the concentration of brine, or those of sulphate of soda, as its agitated solution cools. On submitting to analysis the metallic crystals thus separated, and also the liquid metal deprived of them, we find the former to be lead almost alone, but the latter to be rich in silver, when compared with the original alloy. The more of the crystalline particles are drained from the metallic bath, the richer does the mother liquid become in silver. In practice, the poor lead is raised by this means to the standard of the ordinary lead of the litharge works; and the better lead is made ten times richer. This very valuable alloy is then submitted to cupellation; but as it contains only a tenth part of the quantity of lead subjected to crystallization, the lo in the cupel will be obviously reduced to one-tenth of what it was by the former proce ; that is, 7 ⁄ 10 of a per cent., instead of 7. These nine-tenths of the lead separated by the drainer, are immediately sent into the market, without other lo than the trifling one, of about 1 ⁄ 2 per cent., involved in reviving a little dro skimmed off the surface of the melted metal at the beginning of the operation. Hence the total waste of lead in this method does not exceed 2 per cent. And as only a small quantity of lead requires to be cupelled, this may be done with the utmost slowne and circumspection; whereby lo of the precious metal, and injury to the health of the workpeople, are equally avoided. The crystallization refinery of Mr. Pattinson is an extremely simple smelting-house. It contains 3 hemispherical cast-iron pans, 41 inches in diameter, and 1 ⁄ 4 of an inch thick. The three pans are built in one straight line, the broad flange at their edge being supported upon brickwork. Each pan has a discharge pipe, proceeding laterally from one side of its bottom, by which the melted metal may be run out when a plug is withdrawn, and each is heated by a small separate fire. Three tons of the argentiferous lead constitute one charge of each pan; and as soon as it is melted, the fire is withdrawn; the flue, grate-door, and ash-pit, are immediately closed, and made air-tight with bricks and clay-lute. The agitation is now commenced, with a round bar of iron terminated with a chisel point, the workman being instructed merely to keep moving that simple rake constantly in the pan, but more especially towards the edges, where the solidification is apt to begin. He must be careful to take out the crystals, progre ively as they appear, with an iron drainer, heated a little higher than the temperature of the metal bath. The liquid metal lifted in the drainer, flows readily back through its perforations, and may be at any rate effectually detached by giving the ladle two or three jogs. The solid portion remains in the form of a spongy, semi-crystalline, semi-pasty ma . The proportion of crystals separated at each melting, depends upon the original quality of the alloy. If it be poor, it is usually divided in the proportion of two-thirds of poor crystals, and one-third of rich liquid metal; but this proportion is reversed if the alloy contain a good deal of silver. Let us exemplify, by the common case of a lead containing 10 ounces of silver per ton. Operating upon three tons of this alloy, or 60 cwt., containing 30 oz. of silver, there will be obtained in the first operation — | ( a ) | 40 cwt. at | 4 | 1⁄4 | ounces of silver per ton; | in whole | 9 | oz. | | - | 30 oz. | | ( b ) | 20 cwt. at | 21 | | — | — | 21 | | Each of these alloys ( a ) and ( b ) will be joined to alloys of like quality obtained in the treatment of one or several other portions of three tons of the primitive alloy. Again, three tons of each of these rich alloys are subjected to the crystallization proce , and thus in succe ion. Thus poorer and poorer lead is got on the one hand, and richer and richer alloys on the other. Sometimes the mother metal is parted from a great body of poor crystals, by opening the discharge-pipe, and running off the liquid, while the workman keeps stirring, to facilitate the separation of the two. 25 fodders, 15 cwts., 49 lbs. = 540 cwts., 49 lbs. of alloy, holding 5 oz. of silver per fodder, in the whole 130 oz., afforded, after three succe ive crystallizations — | oz. | | 440 | cwts. of | poor lead, | holding 1⁄2 oz. of silver per fodder; in all | 10 | 1⁄2 | | 15 | cwt. 49 | — | holding the original quantity, nearly | 3 | 1⁄2 | | 84 | cwts. of | lead for the cupel, holding 29 oz. | 116 | | | Total | | 130 | | | 1 cwt. of lo , principally in the reduction of dro . | The expenses of the new method altogether, including 3 s. per fodder of patent dues are about one-third of the old; being 17 l. 13 s. and 54 l. 16 s. respectively, upon 84 cwts. of lead, at 29 oz. per fodder. In the conditions above stated, the treatment of argentiferous lead occasions the following expenses :— | FOR ONE FODDER. | £ | s. | d. | | By the | new proce | 0 | 13 | 7 | | old proce | 2 | 2 | 2 | Admitting that the treatment of silver holding lead is economically po ible only when the profit is equal to one-tenth of the gro expenses of the proce , we may easily calculate, with the preceding data, that it is sufficient for the lead to have the following contents in silver :— | With the new proce , 3 ounces per fodder; or, | 0·000078 | | With the old proce , 84⁄10 ounces per fodder; or, | 0·000218 | To conclude, the refining by crystallization reduces the cost of the parting of lead and silver, in the proportion of 3 to 1; and allows of extracting silver from a lead which contains only about 3 oz. per ton. In England, the new method produces at present very advantageous results, especially in reference to the great ma es to which it may be applied. In 1828, the quantity of lead annually extracted from the mines in the United Kingdom had been progre ively raised to 47,000 tons. Reduced almost to one-half of this amount in 1832, by the competition of the mines of la Sierra de Gador, the English production began again to increase in 1833. In 1835, 35,000 tons of lead were obtained, one-half of which only having a mean content of 8 1 ⁄ 2 oz. of silver per ton, was subjected to cupellation, and produced 14,000 oz. of that precious metal. The details of this production are — | Silver extracted from 17,500 tons of lead, holding upon the average 81⁄2 oz. per ton. | 140,000 | oz. | | Silver extracted from silver ores, properly so called, in Cornwall | 36,000 | | | 176,000 | | In 1837, the production of lead amounted probably to 40,000 tons; upon which the introduction of the new method would have the effect not only of reducing considerably the cost of parting the 20,000 tons of lead containing 8 oz. of silver per ton, but of permitting the extraction of 4 or 5 oz. of silver, which may be supposed to exist upon an average in the greater portion of the remaining 20,000 tons. Otherwise, this ma of the precious metal would have had no value, or have been unproductive. There are two oxides of silver; called argentic oxide, and suroxide, by Berzelius. 1. The first is obtained by adding solution of caustic pota a, or lime-water, to a solution of nitrate of silver. The precipitate has a brownish-gray colour, which darkens when dried, and contains no combined water. Its specific gravity is 7·143. On exposure to the sun, it gives out a certain quantity of oxygen, and becomes a black powder. This oxide is an energetic base; being slightly soluble in pure water, reacting like the alkalis upon reddened litmus paper, and displacing, from their combinations with the alkalis, a portion of the acids, with which it forms insoluble compounds. It is insoluble in the caustic lyes of pota a or soda. By combination with caustic ammonia, it forms fulminating silver . This formidable substance may be prepared by precipitating the nitrate of silver with lime-water, washing the oxide upon a filter, and spreading it upon gray paper, to make it nearly dry. Upon the oxide, still moist, water of ammonia is to be poured, and allowed to remain for several hours. The powder which becomes black, is to be freed from the supernatant liquor by decantation, divided into small portions while moist, and set aside to dry upon bits of porous paper. Fulminating silver may be made more expeditiously by di olving the nitrate in water of pure ammonia, and precipitating by the addition of caustic pota a lye in slight exce . If fulminating silver be pre ed with a hard body in its moist state, it detonates with unparalleled violence; nay, when touched even with a feather, in its dry state, it frequently explodes. As many persons have been seriously wounded, and some have been killed, by these explosions, the utmost precautions should be taken, especially by young chemists, in its preparation. This violent phenomenon is caused by the sudden production of water and nitrogen, at the instant when the metallic oxide is reduced. The quiescent and divellent affinities seem to be so nicely balanced in this curious compound, that the slightest disturbance is sufficient to incite the hydrogen of the ammonia to snatch the oxygen from the silver. The oxide of silver di olves in gla y fluxes, and renders them yellow. It consists, according to Berzelius, of 93·11 parts of silver, and 6·89 of oxygen. 2. The suroxide of silver is obtained by pa ing a voltaic current through a weak solution of the nitrate; it being deposited, of course, at the positive or oxygenating pole. It is said to crystallize in needles of a metallic lustre, interlacing one another, which are one-third of an inch long. When thrown into muriatic acid, it causes the disengagement of chlorine, and the formation of chloride of silver; into water of ammonia, it occasions such a rapid production of nitrogen gas, with a hi ing sound, as to convert the whole liquid into froth. If a little of it, mixed with phosphorus, be struck with a hammer, a loud detonation ensues. With heat it decrepitates, and becomes metallic silver. Sulphuret of silver, which exists native, may be readily prepared by fusing the constituents together; and it forms spontaneously upon the surface of silver exposed to the air of inhabited places, or plunged into eggs, especially rotten ones. The tarnish may be easily removed, by rubbing the metal with a solution of cameleon mineral , prepared by calcining peroxide of manganese with nitre. Sulphuret of silver is a powerful sulpho-base; since though it be heated to redne in close ve els, it retains the volatile sulphides, whose combinations with the alkalis are decomposed at that temperature. It consists of 87·04 of silver, and 12·96 of oxygen. A small quantity of tin, alloyed with silver, destroys its ductility. The best method of separating these two metals, is to laminate the alloy into thin plates, and distil them along with corrosive sublimate. The bichloride of tin comes over in vapours, and condenses in the receiver. Silver and lead, when combined, are separated by heat alone in the proce of cupellation, as described in the article A ay , and in the reduction of silver ores. See suprà . An alloy, containing from one-twelfth to one-tenth of copper, constitutes the silver coin of most nations; being a harder and more durable metal under friction than pure silver. When this alloy is boiled with a solution of cream of tartar and sea-salt, or scrubbed with water of ammonia, the superficial particles of copper are removed, and a surface of fine silver is left. Chloride of silver is obtained by adding muriatic acid, or any soluble muriate, to a solution of nitrate of silver. A curdy precipitate falls, quite insoluble in water, which being dried and heated to dull redne , fuses into a semi-transparent gray ma , called, from its appearance, horn-silver . Chloride of silver di olves readily in water of ammonia, and crystallizes in proportion as the ammonia evaporates. It is not decomposed by a red heat, even when mixed with calcined charcoal; but when hydrogen or steam is pa ed over the fused chloride, muriatic acid exhales, and silver remains. When fused along with pota a (or its carbonate), the silver is also revived; while oxygen (or also carbonic acid) gas is liberated, and chloride of pota ium is formed. Alkaline solutions do not decompose chloride of silver. When this compound is exposed to light, it suffers a partial decomposition, muriatic acid being disengaged. See A ay by the humid method . The best way of reducing the chloride of silver, says Mohr, is to mix it with one-third of its weight of colophony (black rosin), and to heat the mixture moderately in a crucible till the flame ceases to have a greenish-blue colour; then suddenly to increase the fire, so as to melt the metal into an ingot. The subchloride may be directly formed, by pouring a solution of deuto-chloride of copper or iron upon silver leaf. The metal is speedily changed into black spangles, which, being immediately washed and dried, constitute subchloride of silver. If the contact of the solutions be prolonged, chloride would be formed. The bromide, cyanide, fluoride, and iodide of silver, have not been applied to any use in the arts. Sulphate of silver may be prepared by boiling sulphuric acid upon the metal. See Refining of Gold and Silver . It di olves in 88 parts of boiling water, but the greater part of the salt crystallizes in small needles, as the solution cools. It consists of 118 parts of oxide, combined with 40 parts of dry acid. Solutions of the hyposulphite of pota a, soda, and lime, which are bitter salts, di olve chloride of silver, a tastele substance, into liquids po e ed of the most palling sweetne , but not at all of any metallic taste. The iodide of silver is remarkable, like some other metallic compounds, for changing its colour alternately with heat and cold. If a sheet of white paper be washed over with a solution of nitrate of silver, and afterwards with a somewhat dilute solution of hydriodate of potash, it will immediately a ume the pale yellow tint of the cold silver iodide. On placing the paper before the fire, it will change colour from a pale primrose to a gaudy brilliant yellow, like the sun-flower; and on being cooled, it will again resume the primrose hue. These alternations may be repeated indefinitely, like those with the salts of cobalt, provided too great a heat be not applied. The pre ure of a finger upon the hot yellow paper makes a white spot, by cooling it quickly. Fulminate of silver is prepared in the same way as Fulminate of Mercury , which see. On the 10th of February, 1798, the Lords of the Privy Council appointed the Hon. Charles Cavendish, F. R. S., and Charles Hatchett, Esq., F. R. S., to make investigations upon the wear of gold coin by friction. Their admirable experiments were begun in the latter end of 1798, and completed in April 1801, having been instituted and conducted with every mechanical aid, as devised by these most eminent chemical philosophers, and provided, at no small expense, by the government. The following are the important conclusions of their official report:— [54] [54] It is inserted in the Philosophical Transactions for 1803. “Gold made standard by a mixture of equal parts of silver and copper, is not so soft as gold alloyed only with silver; neither is it so pale; for it appears to be le removed from the colour of fine gold, than either the former or the following metal. “Gold, when alloyed with silver and copper, when annealed, does not become black, but brown; and this colour is more easily removed by the blanching liquor, or solution of alum, than when the whole of the alloy consists of copper. It may also be rolled and stamped with great facility; and, under many circumstances, it appears to suffer le by friction than gold alloyed by silver or copper alone. “If copper alone forms the alloy, it must be di olved and separated from the surface of each piece of coin, in the proce of annealing and blanching. “Upon a comparison of the different qualities of the three kinds of standard gold, it appears (strictly speaking) that gold made standard by silver and copper is rather to be preferred for coin.” It will, undoubtedly, seem not a little strange to the uninitiated, that this report, and its important deductions, should have been of late years entirely set at nought, without any scientific reason or research, apparently for the purpose of giving a certain official in our Mint a good job, in sweating out all the silver from our sovereigns, and replacing it, in the new coinage, with copper, taking on an average 3 d. worth of silver out of each ounce of our excellent gold coin, and charging the country 6 1 ⁄ 2 d. for its extraction, besides the very considerable expense in providing fine copper to replace the silver. The pretence set up for this extraordinary degradation of the gold, was, that our coin might peradventure be exported, in order to be de-silvered abroad, a danger which could have been most readily averted, by leaving out as much gold in every sovereign as was equivalent to the silver introduced, and thus preserving its intrinsic value in precious metal. When the film of fine gold which covers each of our present pieces has been rubbed off from the prominent parts, these must appear of a very different and deeper colour than the flat part or ground of the coin. “The reason, therefore, is sufficiently apparent, says Mr. Hatchett, why gold which is alloyed with silver only, cannot be liable to this blemish;” and with one-half of silver alloy, it must be much le liable to it, than with copper alone. Why did the political economists in the recent Committee of the House of Commons on the Mint, blink this question, of public economy and expediency? Gold, as imported from America, Asia, and Africa, contains on an average nearly the right proportion of silver for making the best coin; and were it alloyed to our national standard, of 22 parts of gold, 1 of silver, and 1 of copper, as defined by Me rs. Cavendish and Hatchett, then by simply adding the deficient quantities of one or two of these metals, by the rule of alligation, the very considerable expense would be saved to the nation, and sulphureous nuisance to the Tower Hamlets, now foolishly incurred in de-silvering and cuprifying sovereigns at the Royal Mint. It was long imagined in Europe, that the average metallic contents of the silver ores of Mexico and Peru, were considerably greater than those of Saxony and Hungary. Much poorer ores, however, are worked among the Cordilleras than in any part of Europe. The mean product of the whole silver ores that are annually reduced in Mexico, amounts only to from 0·18 to 0·25 of a per cent.; that is, from 3 to 4 ounces in 100 lbs.; the true average being, perhaps, not more than 2 1 ⁄ 2 . It is by their greater profusion of ores, not their superior richne , that the mines of South America surpa those of Europe. Gold and Silver produced in Forty Years, from 1790 to 1830. | Gold. | Silver. | | Mexico | £ 6,436,453 | £ 139,818,032 | | Chile | 2,768,488 | 1,822,924 | | Buenos Ayres | 4,024,895 | 27,182,673 | | Ru ia | 3,703,743 | 1,502,981 | Returns of the Dollars coined at the different Mints in Mexico . | 1829. | 1830. | 1831. | 1834. | | Mexico | 1,280,000 | 1,090,000 | 1,386,000 | 952,000 | | Guanajuato | 2,406,000 | 2,560,000 | 2,603,000 | 2,703,000 | | Zacatecas | 4,505,000 | 5,190,000 | 4,965,000 | 5,527,000 | | Guadalaxara | 596,000 | 592,000 | 590,000 | 715,000 | | Durango | 659,000 | 453,000 | 358,000 | 1,215,000 | | San Luis | 1,613,000 | 1,320,000 | 1,497,000 | 928,000 | | Ilalpan | 728,000 | 90,000 | 323,000 | — | | Total | 11,787,000 | 11,295,000 | 11,722,000 | 12,040,000 | | The returns for 1832 and 1833 are wanting. | Peru. — Returns of Gold and Silver coined at the Mints of Lima and Casco. | Gold. | Silver. | Total, in Dollars. | | 1830 | 180,000 | 2,015,000 | 2,195,000 | | 1831 | 92,000 | 2,384,000 | 2,476,000 | | 1832 | 94,000 | 3,210,000 | 3,284,000 | | 1833 | 150,000 | 2,990,000 | 3,140,000 | | 1834 | 110,000 | 3,150,000 | 3,260,000 | Returns of Silver in Bars produced at the different Smelting-works in Peru . | Lima. | Truxillo. | Pasco. | Aya- cucho. | Puno. | Are- quip a. | Total, in Dollars. | | 1830 | 270,000 | 190,000 | 780,000 | 120,000 | 250,000 | 150,000 | 1,760,000 | | 1831 | 270,000 | 60,000 | 1,110,000 | 70,000 | 310,000 | 110,000 | 1,930,000 | | 1832 | 290,000 | 100,000 | 1,800,000 | 70,000 | 345,000 | 25,000 | 2,640,000 | | 1833 | 222,000 | 70,000 | 2,130,000 | 50,000 | 25,000 | 65,000 | 2,562,000 | Returns of Silver in Dollars exported from the Provinces of Chili . | Coquimbo. | Huasco. | Copiano. | | 1831 | 785,000 | 115,000 | 670,000 | | 1832 | 316,000 | — | 36,000 | | 1833 | 490,000 | 100,000 | 585,000 | | 1,591,000 | 215,000 | 1,291,000 | Santiago —Mint Coinage. | Gold. | Silver. | Total. | | 1832, 174,000; 1833, 392,500 | 1832, 42,000; 1833, 92,000 | 700,500 | The production of Silver in the kingdom of Saxony , amounted to — | 59,231 | marcs | and | 8 | loths, | in the year | 1825 | | 55,023 | — | | — | 1826 | | 60,034 | — | | — | 1827 | | 61,361 | — | | — | 1828 | | 65,176 | — | and | 10 | loths | — | 1830 | | 65,886 | — | | — | 1832 | The mine of Himmelsfürst alone produces annually 10,000 marcs. The quantity of Silver produced in the Pru ian states was — | 22,135 | marcs in | 1825 | | 20,071 | — | 1826 | | 18,631 | — | 1827 | | 21,731 | — | 1828 | | 20,612 | — | 1829 | | 20,887 | — | 1830 | | 19,031 | — | 1831 | | 22,083 | — | 1832 | The whole annual production of Europe, and Asiatic Ru ia, has been rated by Humboldt at 292,000 marcs; by other authorities, at 310,000; while at the beginning of the present century, that of the Spanish colonies in America was 3,349,160 marcs, or nearly twelve times as much. The sum total is 3,704,160 marcs, of 3609 grains troy each; which is nearly 1,900,000 lbs. avoirdupois; that is, little le than 9000 tons. The English Mint silver contains 222 pennyweights of fine silver, and 18 of copper, in the troy pound of 240 pennyweights; or 92·5 in 100 parts. 1 pound troy = 5760 grains, contains 65·8 shillings, each weighing 87·55 grains. The French silver coin contains one-tenth of copper, and a franc weighs 5 grammes = 77·222 grains troy. The Pru ian dollar, ( thaler ), is the standard coin; 10 1 ⁄ 2 thaler weigh 1 marc; hence, 1 thaler weighs 343·7 grains troy, and contains 257·9 grains of fine silver; being 75 per cent. of silver, and 25 of alloy. The Austrian coin contains 13 ⁄ 288 of alloy, according to Was ser berg; which is only 4 1 ⁄ 2 per cent.