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fine iron for sword-blades, and curious cali- ry and gold, and is afterwards heated in a proper coes and chintzes. Hydrabad is the capital. vessel to about the temperature of boiling water
GOLCONDA, a celebrated fortress in the for three or four days. Finally, the mixture is country of the same name, situated about six washed very carefully by small parcels at a time, miles W. N. W. of Hydrabad, and joined to the earthy particles are carried off by the water, that city by a wall of communication. It oc- bined with the gold into an amalgam. Part of
and there remaios behind only the mercury comcupies the summit of a hill of a conical form, the mercury is then separated by pressure in a and is deemed impregnable.
leathern bag, and the rest is driven off by distilGOLD Of this metal we have already treat. lation, leaving behind only the gold and the siled in a mineralogical and systematic view under the ver with which it may happen to be alloyed. article AURUM. It yet remains for us to contem- Native gold is thus extracted from its ore. plate it in a metallurgic point of view, and as ap- But a much more complicated process is required propriated to the arts and the purposes of coin. to separate that portion of the metal which is
Metalurgic processes. The richest gold mines, dispersed invariably in the pyrites, ochre, galena, concerning which we have any particular descrip- and other metallic substances, as well as the tion, are those of Hungary ; ad we shall hence stony parts of the gangue. These, in the sosting pay some attention to these establishments. The already described, are separated not on.y ac high commercial value of gold, compared with cording to their apparent richness, but, what is that of every other metal, depends in a consider- of more importance, are also arranged according able degree on its rarity; hence even the most to their hardness. profitable veins of gold are of trifling magnitude, This being completed, they are transferred to and will pay very well to the miner, though inti- the stamping mill, which is a complicated machia mately mixed with so large a proportion of stony Dery that first pounds them into a very fine or gangue and other impurities as would render it coarser powder, according to the nature of the impossible to work any other metal similarly combination, the pounding being never carried circumstanced. In the Hungarian mines the to a finer result than is absolutely necessary; af. attention of the miner is not confined to the ter which the pulverised matter is, by the same strings of ore, but the whole contents of the vein machinery, washed, in consequence of the admisare usually extracted. It is raised for the most sion of a stream of water into the coffer that part in large masses to the surface, and is then contains it, into shallow channels or troughs of va. distributed to the workmen, who break it first rious dimensions, constructed either of wood or with large hammers, and afterwards with smaller stone, and communicating at their extremities ones till it is reduced to pieces of the size of a with each other, the whole series being called a walnut or less. During this process each piece is labyrioth; these are separated from each other attentively examined and arranged according to by sliders; and when the material of greatest its value.' The native gold, even to the smallest specific gravity, and which may first be supposed visible grain, is separated as accurately as possi- to settle, has deposited, another slider is added, ble from the quarter in which it is chiefly inbed. and fresh portion of water admitted from the ded, and put by itself: the auriferous galena cofler. After which another labyrinth is opened, and pyrites are also thrown into separate heaps. and then a third, ull the whole are progressively The small splinters decached during this process, filled, taking care not to mix what has been de as well as the sand and mud of the mine, are also posited in one channel with what has been de collected, washed, and sifted, and arranged ac. posited in the others. After this the one is accu. cording to their fineness and apparent richness. rately mingled with a little quick lime by way
of The portion rejected in this tirst examination is flux, and with galena proportioned to the quasafterwards re-examined by boys, whose time is of tity of gold and silver that the pyrite (where little value, and who pick out nearly the whole much pyrite exists) is found to contain according of what has been overlooked by the men, and to the result of a previous essay. The mixture sort it in the manner just mentioned.
being next placed in a reverberating furnace is · The native gold with its adhering matrix is made red hot, and, as soon as it begins to clot again broken by hand into still smaller pieces, together, is stirred up from time to time, and kept by which an additional quantity of impurities at a temperature inadequate to its fusior, till and stony matter is got rid of: it is then put into part of the sulphur is driven off : this being efa kind of wooden box, Moored with cast iron fected, the fire is increased, the whole is brought plates, and reduced to a heavy powder by the to a state of thin fusion, and then let out into a action of two or more heavy spars of oak 'shod mould of sand. It is afterwards broken into with iron, and worked alternately in the man. small pieces, and roasted and fused once or twice ner of a common stamping mill. "This powder, more, till all the sulphur and other impurities or flour, as it is called, being now removed into are got rid of, and nothing remains but the varia convenient vessel like a large bason, is mixed ous inetals with which it is combined, usually with a sufficient quantity of salt and water to silver
and copper, but occasionally lead, antimorender it damp, after which a workman takes a ny, platina, and iron. thin porous leather bag, puts a quantity of mer. The separation of gold from these metals comcury into it, and by a continued regular pressure stitutes the process of refining. Lead is sepaforces the mercury in minute drops, like dew, rated upon a large scale, by what is called through the leather: in this minutely divided testing, or converting the lead into a vitreous state it falls upon the pulverised ore, and is im- oxyd : antimony by the use of sulphur, which, mediately kneaded up with it till the requisite while it will not unite with the gold, converts the quantity (depending in a great mcasure on the antiinony into a suiphuret. This sulphuret of proportion of gold) has been added. This part antimony may be afterwards employed to see of the process being completed, the mixture is parate goid from silver, as well as from the iin, rubbed together by a wooden pestle for some perfect metals. While it is usually separated time to expedite the incorporation of the mercu- from platina by mercury, which unites less rea.
dily with platina than with gold, and of leability to reduce it into leaves of an almost course leaves the platina pure. The gold is af- incredible thinness; 'o that in this state, notwith-terwards separated from the mercury by disti!- standing its high specific gravity, it will float in lation.
the air like a feather. Of the ingenious art called sioplication of Gold lo a variety of the arts.-Under gold-beating, we shall proceed to give a short this head we shall consider the processes of gold- account. beating and gilding in general.
The gold selected for this purpose is as pure as Gold-beating, including the mode of manufac- possible; the quantity used at one time by the turing gold leaf and gi!l wire.
English artists is two ounces. This being melted The colour of pure gold, by reflected light, is in a black-lead crucible with some borax, is a full bright yellow, verging on one hand towards poured into an iron mould, previously heated and o ange, and on the other towards brass yellow: grcased, by which it is formed into a plate six or it is remarkable that gold fused with borax be. eight inches long, and three quarters of an incha comes considerably paler than usual, and, on wide. This plate is heated red hos, in order to the other hand, when fused with nitre, it becomes burn off the tallow, and is then extended by forgmore highly coloured, without any other percep. ing on an anvil, and afterwards passed between tible change being induced by either of these steel rollers, till it becomes a long ribband as thin salts; hence as this metal is reckoned beautiful in as paper. The ribband is now cut into 150 equal proportion to the fullness and brilliancy of its pieces, each of which is forged on an anvil, till colour, the borax Nux used by the goldsmiths is it is about an inch square, after which they are generally mixed with a sufficient quantity of nitre well annealed. Each of the squares in this to counterbalance its discolouring property. The state weighs six grains and four tenths, and in colour of gold, when in high fusion, is blueish thickness is equal to tz of an inch. The 150 plates green, of nearly the same tint with that of gold of gold thus produced are interlaid with pieces by transmitted light : this latter may cocvenient- of very fine vellum, about four inches square, ly be observed by laying a leaf of gold between and about twenty ellum leaves are placed on two chin plates of colourless glass, and holding the outsides; the whole is then put into a case it between the eye and a strong light.
of parchment, over which is drawn another siThe specific gravity of gold is only inferior to milar case, so that the packet is kept close and that of platina : with regard to its precise amount tight on all sides. Being now laid on a smooth a considerable variation may be observed on com- block of marble, from 200 to cov Ibs. in weight, paring the reports of different authors, one the heavier tle better, the workrian begins the stating it as high as 20, and another as low as beating with a round-faced somewhat convex 18-75. This difference is no doubt in part attri- hammer, called the catch hammer, weighing butable to slight impurities in the gold itself, sixteen pounds; the packet is turned occasionally partly also to imperfection in the balances made upside down, and beaten with strong but not use of, to differences of temperature, to the gold's acute strokes, till the gold is extended nearly to being cast in sand or metal, to its being hammer- an equality with the vellum leaves, to ascertain ed or not, and to other causes, which, in the arti- which the packet is opened fion time to time, cle Alloy, we have briefly pointed out as affect. and also bent and rolled between the hands to ing the specific gravity of metallic substances. facilitate the extension of the gold between the According to an experiment by Mr. Ellicot, leaves. This first part of the process being whose accuracy is well known, the specific gravi- completed, the packet is then taken to pieces, and ty of an ingot of gold refined by antimony was each leaf of gold is divided into four, with a steel =19.184, and of the same, when hammered, knife; the 600 pieces thus produced are interlaid 19.207. According to Lewis, the specific gravity with pieces of oxgut, of the same dimensions, of fioe goid at 55° Fah. amounted to 19.376. and used in the same manner as the vellum. The Brisson reports the specific gravity of fine gold beating is continued, but with a lighter hatoia ingot to be=19-258, and the sanie, when ham- mer, called the shoddering hammer, and weighing mered, =19°361. In hardness this metal ranks about twelve pounds, till the gold is brought to somewhat above silver and below copper. It is the same dimensions as the interposed membrane. extremely flexible, and so tough, that, when at It is now again divided into four, by means of a length by repeated bending it is made to break, piece of cane cut to an edge, the leaves being by both the fractured pieces appear terminated by a this time so light, that any accidental moisture, wedge-shaped extremity. From its softness and conder.sing on an iron blade, would cause them toughness it receives, with perfect exactpess, the to adhere to it. The 2400 hence resulting are impression of the dies in coining, and, for the parted into three packets, with interposed same reasons, it does not file freely, clogging up membrane as before, and beaten with the finishzhe teeth of the instrument in a very short time. ing or guld hammer, weighing about ten pounds, It possesses little elasticity or sonorousness. It till they acquire an exec:it equal to the former. receives great brilliance from the burnisher, but the packets are now taken to pieces, and the not from the action of polisbing powders. It is gold leaves, by means of a cane instrument and inodorous and insipid. "The tenacity of gold is the breath, are laid flat on a leathern cushion, by no means so great as was supposed by the and cut one by one, to an even square, by a cane earlier chemists; it is inferior in this respect to frame; they are lastly laid in books of 25 leaves iron, copper, platina, and silver. A wire of gold, each, the paper of which is previously smoothed, iš of an inch in diameter, will support about and rubbed with red bole, io prevent them from 254 lbs. of avoirdupois, before it breaks. It is adhering. Hence it appears, that each of the inch extremely malleable both when hot and cold, and square pieces, into which the ribband of gold was very ductile.
divided, is extended, by beating, to 196 square In consequence of the high commercial value inches, or 16 leaves, weighing 0.4 of a grain of gold, it is scarcely ever employed in mass, or each, and not exceeding in thickness or of an in thick plates, for ornamental purposes ; but inch. Each grain of gold furnishes 30°C square advantage has been taken of its remarkable mal. inches.
Gold wire, as it is called, is in fact only silver better: that it may work freely, it is to be mixed, wire gilt, and is prepared in the following manner: previously to being used, with a little oil of tur. A solid cylinder of fine silver, weighing about pentine, till it is brought to a proper consistence. twenty pounds, is covered with thick leaves of gold, If the gold size is good, it will be sufficiently dry which are inade to adhere inseparably to it by in twelve hours, more or less, to allow the artist means of the burnisher: successive laminæ are to proceed to the last part of the process, which thus applied, till the quantity of gold, if intended is the application of the gold. For this purpose, for common gold wire, amounts to 100 grains for a leaf of gold is spread on the cushion (formed by every pound troy of silver; if for double gilt wire, a few folds of flannel, secured on a piece of wood to about 140 grains.
about eight inches square by a tight corering of This gilt silver rod is then drawn successively leather), and is cut into strips of a proper size, by through holes made in a strong steel plate, till it is a blunt parallel knife; each strip being taken up reduced to the size of a thick quill
, care being on the point of a fine brush, is applied to the part taken to anneal it accurately after each operation. intended to be gilded, and is then gently pressed The succeeding process is similar to the former, down by a ball of soft cotton; the gold immediateexcept that a mixed metal, somewhat softer than ly adheres to the sticky surface of the size, and steel, is employed for the drawing plates, in order after a few minutes, the dexterous application of to prevent the gilding from being stripped off, and a large camel's hair-brush sweeps away the loose no further annealing is requisite, after it is brought particles of the gold leaf without disturbing the to be as slender as a crow quill. When the wire rest. In a day or two the size will be completely
spun as thin as is necessary, it is wound on a dried, and the operation is foished. The advashollow copper bobbin, and carefully annealed by a tages of this met of gilding are that it is very very gentle heat: finally, it is passed through a simple, very durable, not readily injured by changes Patting-mill, and the process is complete.
of weather, even when exposed to the open air, According to Dr. Halley, six feet in length of and when soiled it may be cleaned with a little the finest gilt wire before flatting, will counterpoise warm water and a soft brush; its disadvantage is no more than a grain: and as the gold is not quite that it cannot be burnished, and therefore wants
of the whole, a single grain of gold thus extend the high lustre produced by the next method. Its ed will be 345.6 feet long. By the operation of chief employment is in out-door work, Burnished fatting, the length of the wire is increased about gilding, or gilding in distemper, is thus performed: a seventli, and its width is equal to st of an inch: the surface to be gilt must first be carefully covered hence the surface occupied by one grain is equal with stroug size, made by builing down pieces of to 98.7 square inches, with a thickness of one of white leather, or clippings of parchment, till they an inch.
are reduced to a stiff jelly; this coating being driel, Gilding in general.- One of the most valuable eight or ten more must be applied, consisting of the properties of gold is, that of its extreme ductili- same size, mixed with fine Paris plaster, or washed ty, which we have just noticed, for without this, chalk; when a sufficient number of layers have it could seldom, on account of its dearness, be . been put on, varying according to the nature of employed in substance, and its ornamental use the work, and the whole is become quite dry, a would be extremely limited. It is in consequence moderately thick layer must be applied, composed of this property, that we are able to cover almost of size and bole, or yellow ochre; while this last any substance with layers almost infinitely fine, is yet moist, the gold leaf is to be put on in the and to make them assume the appearance and usual manner; it will immediately adhere on being possess the extreme beauty of this precious metal. pressed with the cotton ball, and, before the size And on this the art of gilding depends.
is become perfectly dry, those parts which are irThe materials of gilding, or rather the different tended to be the most brilliant are to be carefulstates in which gold is used for this purpose, are ly burnished with an agaie or dog's tooth. In the following: leaf-gold of different thicknesses, order to save the labour of burpisbing, it is a and formed either of the pure metal, or of an alloy common but bad practice slightly to burnish the of this with silver, amalgam of gold, and gold brilliant parts, and to deaden the rest by drawing powder. Gilding is performed either with or over them a brush dipped in size ; the required without the application of heat. By the first of contrast between the polished and unpolisher gold these methods, those substances are gilt which are is indeed thus obtained, but the general effect is not liable to attraction by exposure to a moderate greatly inferior to that produced in the regular hcat, such as metals, and sometimes glass and way, and the smallest drop of water falling on the porcelain: the second method is practised with sized part occasions a stain. This kind of gildthose substances, such as wood, paper, leather, ing can only be applied on in-door work, as rain, silk, lacquered and japanned ware, &c. which and even a considerable degree of dampness, will would bu injured and even destroyed at the tem- cause the gold to peel off. When dirty it may be perature requisite for gilding the fornier. This cleaned with a soft brush, and hot spirits of wine, last is the simplest method, and we will describe or oil of turpentine. It is chiefly used ou pictureit before we proceed to the art of gilding by beat, frames, mouldings, and stucco.
On wood there are two methods of gilding, viz.. Letters written on vellum or paper are gilded in oil-gilding, and burnished gilding. The first is three ways: in the first, a little size is mixed with thus performed: the wood must first be covered or the ink, and the letters are written as usual ; when primed with two or three coatings of boiled linseed they are dry, a slight degree of stickiness is prooil and white lead, in order to fill up the pores and duced by breathing on them, upon which the gold conceal the irregularities of the surface occasion. leaf is immediately applied, and by a little presed by the veins in the wood. When the priming sure may be made to adhere with sufficient firm. js quite dry, a thin coat of gold size must be laid Dess: in the second method some wbite lead or on. This is prepared by grinding together some chalk is ground up with strong size, and the let. strongly calcined red ochre with the thickest dry. ters are made with this by means of a brush; ing oil that can be procured, and the older the when the mixture is almost dry, the gold leaf may
be laid on, and afterwards burnished: the last gnited merely by the attraction of adhesion submethod is to mix up some gold powder with size, sisting between them. The simplest of all the and make the letters of this by means of a brush. kinds of gilding on metal, and which strikingly The edges of the leares of books are gilded while demonstrates the power of the affinity of adhesion, in the binder's press, by first applying a composic is one that is sometimes practised on plane surtion formed of four parts of Armenian bole, and faces of copper and iron with considerable success. one of sugarcandy, ground together to a proper The metal being previously polished and quite consistence, and laying it on by a brush with clean, is heated to about the temperature of melt. the white of an egg; this coating, when nearly ed lead, and covered with a double layer of gold dry, is smoothed by the burnisher, it is then slight- leaf; by the cautious application of a blood-stong ly moistened with clean water, and the gold leaf burnisher applied gently at first, and increasing applied, and afterwards burbished. In order to the force of the pressure by degrees, the surfaces impress the gilt figures on the leather corers of of gold and copper are brought to touch each other books, the leather is first dusted over with very in almost every point, and then adhere with a force fine powdered rosin or mastich, then the iron tool proportioned to the completeness of the contact. by which the figure is made is moderately heated, The first layer being thus burnished down, a seand pressed down upon a piece of leaf gold, which cond is made to adhere in the same manner, and slightly adheres to it; being then immediately ap- sometimes a third, if the gilding is intended to be plied to the surface of the leather with a certain very solid. The objection to this method of gildforce, the tool at the same time makes an impres- ing is its tediousness, and the almost impossibility sion, and melts the mastich, which lies between the of using a sufficient pressure without injuring the beated iron and the leather; in consequence of this evenness of the gilded surface; where these objecthe gold with which the face of the tool is covered tions do not apply, there cannot be a more effecis made to adhere to the leather, so that, on re- tual mode of giling, as is evident from the manumoving the tool, a gilded impression of it remains facture of gilt silver or copper wire. The bar, bebehind.
fore it is committed to the wire-drawer, is plated Drinking-glasses and other utensils of this ma- with gold, by having several leaves of gold burterial are sometimes, especially in Germany, gilt nished down upon it, and being then subjected to on their edges; this is done in two ways, either by the strong compression that takes place in wire a simple adbesive varnish, or by means of fire. drawing, the gold and the other metal become so The varnish is prepared by dissolving in drying perf-ctly united as to form in a manner but one linseed oil a quantity of gom anime,or, still better, substance. The most usual method of covering of clear amber equal in weight to the oil; a very the surface of a metal with gold is by means of an, drying and adhesive varnish is thus prepared, amalgam, or, as it is technically called, water gildwhich being diluted with a proper quantity of oil ing. If the metal to be gilt is silver, the best way of turpentine is to be applied as this as possible to of proceeding is first to soak it in warın dilute muthose parts of the glass which are to be gilded; riaiic acid, that the surface may be rendered per. vben this is dry, which will be in about a day, the fectly clean; it must then be washed in clean glass is to be placed by the fire side, or in a stove, water changed two or three times to get rid of the till it is so warm as almost to burn the fingers whole acid; being afterwards dried and made mo when handled: at this temperature the varnish will derately warm, a little gold amalgam, also warm, become glutinous, and a piece of leaf gold applied is to be carefully and evenly spread upon the in the usual way will immediately adhere; when silver, to which it will immediateiy adhere: when the gilding is thus put on, and before it is grown this is coinpleted, the piece is piaced upon a conquite cold, it may be burnished, taking care only renient support over a clear charcoal fire, and to juterpose a piece of very thin paper between while the mercury is evaporating, if any specks or the gold and the burnisher. If the varnish is very places appear that have escaped the amalgam, a good, this is the best method of gilding glasses, as sınall piece is to be laid on and spread with a brush the gold is thus fixed on more evenly thau in any to suppiy the deficiency, without removing the other way: it often happens, however, when the article from the fire. Aiter a time the whole of varnish is but indifferent, that by repeated wash- the mercury will be driven off, and the piece, after ing the gold soon wears off; on this account the cooling, being accurately examined, will be found practice of burning in is sometimes bad recourse to be entirely covered with a thin coating of pale to. For this purpose some powdered gold is tem- dull gold. The small roughnesses and loosely adpered with gum water and borax, and in this state hering particles are now to be removed with a applied to the clean surface of the glass with a scratch brush, which is made of some exceedingly fine camel's hair pencil; when quite dry, the glass fine brass wire, bound together into a tuft; by is put into a stove heated to about the tempera- this the surface is rendered perfectly smooth and ture of an annealing oven, the gum burns off, and bright, but it still remains of a pale yellow colour: the borax,by vitrifying,cements the gold with great this defect is next removed by warming the piece firmness to the glass; after which it may be bure and smearing it over with gilder's wax, a composipished. The gilding upon porcelain is in like tion of bees-wax, red ochre, verdigris, and green manner fixed by fire and borax; and this kind of vitriol or alum. The wax being burnt off over a ware,being neither transparent nor liable to soften, charcoal fire, and the piece quenched in urine, the and thus injure its form in a low red heat, is free colour of the gilding will be found to be much from the risk and injury that the finer and more heightened; if it is not sufficiently so by the first' fusible kinds of glass are apt to sustain from such application, a succeeding one will complete the treatment. All the methods of gilding hitherto desired effect; after which the work may be bure described reseinble cach other, by being accom- nished or not, according to the taste of the artist, plished by means of some adhesive medium : this, Instead of the common silder's wax, a mixture of , however, is not the case with gilding upon metals; equal parts of nitre, sal ammoniac, green vitriol, the gold is brought into immediate contact with and verdigris, moistened with water, will answer. the other metal, and they both remain firmly
Copper and the alloys formed by its combina- the production of standard gold, though of a dif. tiun with zinc,are gilded nearly in the same way as ferent character, its bulk will be found remarkably silver; but as their affinity for mercury is consider- greater than would be deduced from the mean speably less than that of silver, it would be difficult cific gravity of its ingredients. to inake the amalgain of gold adhere to the bur. Zinc forins with gold an alloy of a brass-yellow nished surface of these metals by the same means colonr; in other respects its action resembles that of and with the same evenness as takes place in the arsenic. The specific gravity of the compound is case just described, and hence nitric acid is enn- somewhat greater than the calcalated mean, when ployed to facilitate the adliesion of the copper and the zinc constitutes t's
of the mass, mercury : by wbich aid five graios of gold may be Cobalt, mixed with standard gold in the propormade completely to gild toth the upper and under tion of four grains to an ounce, renders the colour surfaces of 144 copper buttons, each of them ar somewhat paler, and induces a slight degree of inch in diameter.
brittleness, but does not materially alter the graIron, or rather steel, is gilt with great difficulty: vity. In the proportion of 33 yrs. to the ounce for if a high heat be employed for this purpose, it renders the gold very britule, and gives it an the temper of the steel will hereby be injured and earthy fracture. reduced too low. One of the best plans lately re
Nickel, mixed in the proportion of 38 grains to commended, is a mixture of sulphuric ether with the ounce, produces an alloy of the colour of tine nitro-muriat of gold: if ether thus charged with brass, with a coarse-grained earthy fracture and gold be spread, by means of a fine brash, on the very brittle: its specific gravity being somewhat surface of highly polished steel, the ether will pre- less than the mean. sently evaporate, and leave the gold bebind in close With manganese, in its black oxyd, gold will comcontact with the steel; at which time the adhesion bine, and produce an alloy of a reddish grey, cawill be considerably improved by an application pable of receiving a brilliant lastre like steel : the of the burnisher. The dearness, and especially mixed metal is exceedingly hard, and so far pos. the rapid volubility of ether, are objections of some sessed of ductility, as to be in some measure flatmoment, but may be got over by using the best oil tened by the hammer before it break's. of turpentine instead of the ether, which has nearly With bismuth, in the proportion of 58 grains to the saine efficacy in decomposing the nitro-mu- the ounce, it yields an alloy of a pale greenish riat of gold; and while much cheaper, is by no yellow, excessively brittle, and exhibiting a finemeans so quickly evaporable.
grained earthy fracture: its specifie gravity someApplication of Gold to the purposes of Coin.-The high what greater than the mean. It standard gold be alvalue of gold renders it at all times expedient to loyed with eren a quarter of a grain of bismuth in preserve it as free from the wash produced by fric. the ounce, the inixture, although in colour aud textion as possible: but more especially so when it is
ture reseinbling gold, is yet perfectly brittle. converted into coin, and thus becomes a standard
Lead, melted with gold, in the proportion of 38 measure of value; and is extremely liable to wear grains in the ounce, gives an alloy externally reout by an incessant circulation.
sembling fine pale gold, but which is as brittle as It is hence constantly alloyed with some other glass, is wholly destitute of metallic lustre, and has råctal that is capable of giving it additional hard
a fine-grained porcellaneous appearance : its spenesss, and in just such a quantity as is sufficient cihc gravity a little less than the mean. The very to produce this effect. In the standard gold of our
fumes of this metal are nearly as prejudicial to the on country, copper is the alloy employed for ductility of gold as those of bismath. this purpose, and the proportion is that of thirty to the ounce, furnis a pale yellow alloy with a
Tin, inixed with gold in the proportion of 38 grs. eight grains to the ounce. mixed, at the same tiine that it is rendered harder, somewhat earthy fracture ; it may be bent without is as ductile as in its state of purity. The colour is breaking, but is very little dactile: its specifie grachanged to a deeper yellow, and its specitic gravity vity is considerably greater than the mean of the is remarkably diminished beyond the mean of it's ingredients. ingredients.
Iron, in the state of bar, cast, or steel, may be This last result is a very extraordinary fact, and combined with gold to the amount of 38 grains, and has led to an examination of the effect produced probably uruch more in the ounce, without impairby an intermixture of gold with other alloys, so as ing its durability: the colour of the alloy is pale to decide which might be most advantageously em- yellowish grey, approaching to dull white; it is ployed as an alloy for geld coin, by enabling the considerably harder than standard gold, and its metal to retain bulk for bulk the nearest approach specific gravity is somewhat less than the mean or to its own specific gravity when pure, at the same
its constituent ingredients. time that it augments its hardn ss, and does not
Platina and gold, when the proportion of the for. detract from its ductility. These enquiries were
mer amounts to 38 grains in the ounce, compose an lately entered upon with great spirit, by Mr. Hat- alloy of a yellowish white colour, like burnished chet and Mr. Cavendish, and the general result of silver, perfectly ductile, but much harder, and conthem has been communicated to and since publish- siderably more elastic, than standard gold. ed by the Royal Society.
Silver may be alloyed with gold in all propor
tions, and occasions hardly any perceptible alter. Arsenic, on account of its volatility, can be com- ation of ductility, hardness, or mean specific grabined with gold only in small proportions. The vity: the colour of the mass becomes paler exactly alloy, or mixed metal hence produced, is of a grey as the quantity of the silver is increased. colour, coarse granular fracture, and very brittle.
Quicksilver and gold unite with the utmost readin' Antimony, mixed by fusion with either fine or ness into an amalgam. The smallest quantity of standard gold in the proportion of not more than the former renders the alloy extremely brittle. $gr. to the ounce, (being not more than us of the Amalgam of gold is of a yellowish white colour, whole mass) will give a brittle compound of a and crystallizes in tetrahedral prisms when comelose granular fracture, with little metallic Justre: posed of six parts of mercury to ope of gold. while, with a change quite as extraordinary as in Copper we have already noticed in speaking of