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Fret tfiem as much as possible from earthy matter s by well washii£, and from sulphur and arsenic by rousting. The ore thus prepared is to be mixed with three parts of black flux, and a little decrepitated sea-salt; nut the mixture in a lined crueible, cover it, and place it in a forge fire, or in a hot furnace, for this ore is"very difficult of fusion.
When well fused, a metallic regulus will be found at the bottom, covered with a scoria of a deep blue colour: as almost all cobalt ores contain bismuth, this is reduced by the same operation as the regulus of cobalt; but as they are incapable of chemically uniting together, they are always found distinct from each other in the crucible. The regulus of bismuth, having a greater specific gravity, is always at th* bottom, and may be separated by a blow with a hammer.
In the humid -way.
Make a solution of the ore in nitrous acid, or aqua regia, and evaporate to dryness; the residuum, treated with the acetous acid, will yield to it the cohaltic part; the arsenic should be first precipitated by the addition of water.
Mercurial oret. The calciform ores of mercury are easily reduced without any addition. A quintal of the ore is put into a retort, and a receiver luted on, containing aome water; the retort is placed in a sand bath, and a sufficient degree of heat given it, to force over the mercury which is condensed in the water of the receiver.
Sulphuretted mercurial oret.
The sulphurous ores are assayed by distillation in the manner above, only these ores require an equal weight of clean iron filings to be mixed with them, to disengage the sulphur, while the heat volatilizes the mercury, and forces it into the receiver. These ores should likewise be tried for cinnabar, to know whether it will answer the purpose of extracting rt from them; for this a determinate quantity of the ore is finely powdered and put into a glass vessel, which is exposed to a gentle heat at first, and gradually increased till nothing more is sublimed. By the quantity thus acquired, a judgment may be formed whether the process will answer. Sometimes this cinnabar is not of so lively a colour as that which is used in trade; in this case it maybe refined by asecond sublimation, and if it be still of too dark a colour, it may be brightened by the addition of a quantity of mercury, Mid subliming it a^ain.
Humid atsay of cinnabar.
The stony matrix should be dissolved in nitrous acid, and the cinnabar being disengaged, should be boiled in 8 or 10 times its weight of aqua regia, composed of Spartsof nitrous, and 1 of marine acid. The mercury may be precipitated in its runniug form by zinc.
Take the assay quantity of the ore finely powdered, and roast it well in a proper degree of heat, frequently stirring it with an iron rod; then add to it about double the quantity of granulated lead, put it in a covered crucible, and place it in a furnace; raise the fire gently at first, and continue to increase it gradually, till the metal begins to work; if it should appear too thick, make it thinner by the addition of a little more lead; if the metal should boil too rapidly, the fire should be diminished. The surface will be covered by degrees with a mass of scoria, at which time the metal should be carefully stirred with an iron hook healed, especially towards the border, lest any of the ore should remain undissolved; and if what is adherent to the hook when taised lrom the crucible melts quickly tguin, and the extremity of the hook, after it is
grown cold is covered with a thin, shining, smooth crust, the scorification is perfect; but, on the cut,, trary, if while stirring it, any considerable clamminess is perceived in the scoria, and when it adnem to the hook, though red hot, and appears unequally tinged, and seems dusty or rough, with rrains interspersed here and there, the scorification is incomplete; in consequence of which the fire should be increased a little, and what adheres to the hook should be gently beaten off, and returned with .■ small ladle into the crucible again. When the scorification is perfect, the metal should be poured into a cone, previously rubbed with a little tallo», and when it becomes cold, the scoria mar be serrated by a few strokes of a hammer. The button is the produce of the assay.
By cupeUation. Take the assay quantity of ore, roast and grind i» with an equal portion of litharge, divide it into 8 or 3 parts, and wrap each up in a small piece ol paper; put a cupel previously seasoned under a muffle, with about six times the quantity of lead upon it. When the lead begins to work, carefully put one of the papers upon it, and after this is absorbed, put on a second, and so on till the whole quantity is introouced; then raise the fire, and as tne scoria is formed, it will be taken up byth: cupel, and at last the silver will remain alone. This will be the produce of the assay, unless the lead contains a small portion of silver, which may be discovered by nutting an equal quantity of the same lead on another cupel, and working it off at the same time; if any silver be produced it must be deducted from the assay. This is called the witness.
In the humid way.
Boil vitreous silver ore in dilute nitrous acid, using about 25 times its weight, until the sulphur is quite exhausted. The silver may be precipitated from the solution by marine acid, or common salt; 100 grains of this precipitate contain 75 of real silver; if it contain any gold it will remain tubdissolved. Fixed alkalies precipitate the earth} matters, and the Prussian alkali will show if any other metal be contained in the solution.
To atmvthe value of rilver.
The general method of examining the purity of silver is by mixing it with a quantity of lead proportionate to the suppose! portion of'alloy; by testing this mixture, and afterwards weighing tiki remaining button of silver. This is the same process as refining silver by cupcllation.
It is supposed that the mass of silver to be examined, consists of 12 equal parts, called pennyweights; so that "if an ingot weighs an ounce, each of the parts will be l-12th of an ounce. Hence, if the mass of silver be pure, it is called silver of 12 penny-weights; if it contain t-12th of its weight of alloy, it is called silver of 11 penny-weights; it 212ths of its weight be alloy, it is called silver of 10 penny-weights; which parts of pure silver are called 5 penny-weights. It must be observed here, that assayers give the name penny-weight to a weight equal to 24 real grains, which must not he confound*^ w ith their ideal weights. TheassayciV grains .'ire called fine grains. An ingot of fine silver, or silver of 12 penny-weights, contains, then, 288 fine grains; if this ingot contain L-288th of alloy, it is said to be silver of II pennv-weighta and 23 grains; if it contain 4-28 St hs of alloy, it is Mho* to be 11 penny-weights, 20 grains, etc. Xow ti certain real weight must be taken to represent the assay-weights: fur instance, 36 real grains represent 12 fine penny-weights; this is ■undivided intu a sufficient number of other smaller weights, which also represent fractions of fine penny-weights and graius. Thus, 18 real grains represent n fine pen
Tombac. Melt together 16 pounds of copper, 1 pound of tin, and 1 pound of zinc.
Red tombac. Put into * crucible 5J pounds of copper: when fused, add \ pound of zinc: these metals will eomsine, forming an alloy of a reddish colour, but possessing more lustre than copper, and also greater durability.
White tombac. When copper is combined with arsenic,by melting them together in n close crucible, and covering the surface with muriate of soda, to prevent oxidation, a white brittle alloy is formed.
Common pewter. •
Melt in a crucible 7 pounds of tin, and when fused throw in 1 pound of lead, 6 ounces of copper, and 2 ounces of zinc This combination of metals will form an alloy of great durability and tenacity; also of considerable lustre. . Seat pewter. The best sort of pewter consists of 100 parts of tin, and 17 of regulus of antimony. Hard pewter. Melt together 12 pounds of tin, 1 p' md of regulus of antimony, and 4 ounces of copper. Flute-key valves. Fuse in a crucible 4 ounces of lead and 2 ounces of antimony, and cist into a bar. This alloy is of considerable hardness and lustre, and is used by flute manufacturers, (when turned into small buttons in a lathe,) for making valves to stop the keynotes of flutes.
Common solder. Put into a crucible 2 pounds of lead, and when melted, throw in 1 pound of tin. This alloy is that
Generally known by the name of solder. When eated by a hot iron, and applied to tinned iron • itli powdered rosin, it acts as a cement or solder; t is also used to join leaden pipes, etc. Hard tolder.
Melt together 2 pounds of copper, and 1 pound of tin.
Melt together 2 pounds of tin, and 1 of lead.
Put into a crucible 10 pounds of lead, and when It is in a state of fusion, throw in 2 pounds of antimony; these metals, in such proportions, form the alloy of which common printing types are made. The antimony gives a hardness to the lead, without which the type would speedily be rendered useless in a printing press. Different proportions of lead, copper, brass, and antimony, frequently constitute this metal. Every artist has his own proportions, so that the same composition cannot be obtained from different foundries; each boasts of the superiority of his own mixture.
Small types and stereotype plates.
Melt 9 pounds of lead, and throw into the crucible 2 pound" of antimony and 1 pound of bismuth: these metals will combine, forming an alloy of a peculiar quality. This quality is expansion as it oools; it is therefore well suited for the formation of small printing types (particularly when many are cast together to form stereotype plates,) as the whole of the mould is accurately filled with the alloy; consequently there can be no blemish in the letters. If a metal or alloy liable to contract in cooling were to be used, the effect of course would be very different.
Another.—The proprietors of different foundries adopt different compositions for stereotype plates. Some fcrra an alloy of 8 parts of lead, 2 parts of ntimony, and l-8th part of tin. Mode of casting.
For the manufacture of stereotype plates, plaster
of Paris, of the consistence of a batter-pudding b«v fore baking, is poured over the letter-press page and worked into the interstices of the types with r brush. It is then collected from the sides by & slip of iron or wood, so as to lie smooth and con* pact. In about two minutes, the whole mass if hardened into a solid cake. This cake, which n to serve as the matrix of the stereotype plate, ii now put upon a rack in an oven, where it undergoes great heat, so as to drive off superfluous mc.V ture. When ready for use, these moulds, according to their size, are placed in flat cast-iron pots, ami are covered over by another piece of cast-iron perforated at each end, to admit the metallic compnsition intended for the preparation of the stcreon | ■■ plates. The flat cast-iron pots are now fastened in a crane, which carries, them steadily to the metallic-bath, or melting pot, where they are immersed and kept for a considerable time, until all the pores and crevices of the mould are completely and accurately filled. When this has taken place, the pots are elevated from the bath by working the crane, and are placed over a water trough, to cool gradually. When cold, the whole is turned out ot the pots, and the plaster being separated, by hammering and washing, the plates are ready for use; having received the most exact and perfect impression.
Metallic casts from engravings on copper.
A most important discovery has lately been made, which promises to be of considerable uti lity in the fine arts: some very beautiful specimens of metallic plates, of a peculiar composition, have lately appeared under the name of " Cast Xxokavings." This invention consists in taking moulds from every kind of engraving, whether line, roezzotinto, or aquatinta, and in pouring on this mould an alloy in a state of fusion, capable of taking the finest impression. The obvious utility of tins invention, as applicable to engravings which meet v ith a readv sale, and of which great numbers are required, will be incalculable; as it will wholly prevent the expense of retouching, which forms so prominent a charge in all works of an extended sale. No sooner is one cast worn out, than ano'her may immediately be procured from the original plate, so that every impression will be a proof. 1 bus the works of our most celebrated artists may be handed down, tid infinitum, for the improvement and delight of future ages, and will afford at the same time the greatest satisfaction to every lover of tlw fine arts.
Melt together 10 ounces of lead, 6 ounces of bismuth, and 4 drachms of regulus of antimony.
Another.—Melt together 2 pounds of regulus of antimony, 8 ounces of brass, and 10 ounces of tin. Common hard white metal.
Melt together 1 pound of brass, 1J ounce of spelter, and J an ounce of tin.
Melt together 2 parts of tin, and 1 of bismuth. Fusible alloy.
Put into a crucible 4 ounces of bismuth, and when in a state of fusion, throw in 24 ounces of lead, and, 14, ounce of tin; these metal-' will combine, forming an alloy fusible at the temperature of boiling water; the 'lisenvery of which is ascribe' to Sir Isaac Newton. Mould this alloy in bars, and take them to a silversmith's to be made into half a dozen tea-spoons. If one of these be given to a stranger to stir his tea, as soon as it is poured from i.ie tea-pot, he will be not a little surprised to find the spoon melt in the tea-cup.
The fusibility of this alloy is certainly surprising, far the fusing temperature of each of its components, singly is higher than twice that of boiling
Etsmuth fuses at 476°, lead at 612°, and tin fl take the mixture from the fire, and cod it. it 44-2°; whilst water boils at SI 2°. substance mixed with the white of an egg,
Jin other.—Melt together 1 ounce of zinc, 1 ounce' uf bismuth, and 1 ounce of lead; this alloy will be found to be remarkably fusible (although each of the metal*, separately, requires considerable heat to melt it,) and will melt even in hot water: It will likewise remain in a fused state on a sheet of pa\.er, over the flame of a lamp or candle.
AfetoUogmphical application of fumble alloy*. Piute a piece of white paper at the bottom of a china saucer, and let it drv: then write on it with common writing ink, and sprinkle some finelvpowdered gum arabic over the writing, which will produce a slight relief When well dried, brush off the powder that does not adhere, and pour fusible metal into the saucer, taking care to cool it rapidly, that crystallization mar not take place. In this way a counterpart of the writing will be obtained, impressed on the metal. By immersing (he ost in slightly warm water, any adhering gum may oe remoTed, and then, if examined by a glass, the writing may easily be read and seen to be perfect. Afterwards, by using common printer's ink, impressions may be taken from it, all of which will Le true fac-nmUe* of the first writing.
The difficulties in this new application of the fu-
r covering three square feet of
*hen the ink will
in the || in form, the sur
ind break under pressure;
Ca»U from J
A combination of three parts of lead, with 9 of
In making casts with this and similar alloys, it
This composition, with the addition of a small
For cushion* of electrical machinery.
For varnuhing figure;
of bismuth in a erucibl": when melted, add 4 an
very beautiful vsrnish, for plaster figures, hu
On tin-foil, fitly disposed on a fiat table, mertu-
The success of this i the clearness of the glass; and the least dirt or dust on its surface will prevent the adhesion of the amalgam or alloy.
Liquid foil for eilvering glasa globes. Melt together 1 ounce of clean lead, and I r of fine tin, in a clean iron ladle; then immediately add 1 ounce of bismuth. Skim off the dross, remove the ladle from the fire, and before it seta, add 10 ounces of quicksilver. Now stir the whole carefully together, taking care not to breathe ovei it, as the fumes of the mercury are very pernicious Pour this through an earthen pipe into the gbu globe, which turn repeatedly round.
Another.—To 4 ounces of quicksilver, add a? much tin-foil as will become barely fluid wheD mix-d. Let the globe be clean and warm, and inject the quicksilver by means of a pipe at tht aperture, turning it about till it is silvered all over. Let the remaiuder run out, and hang the globe up.
Another.—For this purpose, 1 part of mercury and 4 of tin have been used; but it 2 parts of men cury, I of tin, 1 of lead, and 1 of bismuth, are melted together, the compound which they form will answer the purpose better: either of them must be made in an iron ladle, over a clear 5re, and must be frequently stirred.
Melt together 1 pound of brass, and 4£ ounces of speller.
expose it fused, udd . forming
that generally used alloy, called brass.
Another.—For brass which is to be cast into plates, from which [tans and kettles arc to be made, and wire is to be drawn, braziers use calamine jf the finest sort, instead of pure zinc, and in a greater proportion than when common brass is made; generally 56 lb. of calamine to 34 lb. of copper. Old brass, which has been frequently exposed to the action of fire, when mixed with the copper calamine, renders the brass far more ductile, fitter for the muking of fine wire, than it would be without it; but the l.erman brass, particularly thai of Nuremberg, is, when drawn into wire, said ta be preferable to any made in England, for the strings of musical instrument*.
Put into a crucible 5 ounces of pure copper; when it is in a state of fusion, add 1 ounce ofzinc
Put 4^ lbs. of copper into a crucible, ej to heat in a furnace, and when perfectly fu; l£ lb. ofzinc. The metals will combine, f
These metals combine, forming an alloy not unlike jeweller's gold: pour it into a mould of any
shape. ThU alloy is used for inferior jewellery.
Some use onlv half this quantity of zinc, in which proportion the alloy is more easily worked especially in the making of jewellery.
Another.—Melt together 1 ounce of brass with 1J cr 2 ounces of copper, fused under a coat of charcoal dust.
Prince't metal Melt together 3 ounces of copper, and 1 ounce ■jf zinc: or 8 ounces of brats, and 1 ounce of zinc Another.—Melt in a crucible 4 ounces of copper, and when fused, add 2 ounces of zinc; they will combine and form a very beautiful and useful alloy, called Prince Rupert's metal.
Melt in a elean crucible 7 lbs. of pare copper: when fused, throw into it 3 lbs. of zinc, and 2 lbs. of tin. These metals will combine, forming bronze, which, from the exactness of the impression which it takes from a mould, has, in ancient and modern times, been generally used in the formation of busts, medals, and statues.
Specula of teletcope*.
Melt 7 lbs. of coptier, and when fused, add 3 lbs. of zinc, and 4 lbs. of tin. These metals will combine to form a beautiful alloy of great lustre, and of a light yellow colour, fitted to be made into specula for telescopes. Mr Mudge used only copper and grain tin, in the proportion of 2 lbs. to J 4} ounces.
Melt together 112 lbs. of Bristol brass, 14 lbs. of spelter, and 7 lbs. of block tin.
Another.—Melt together 9 parts of copper and 1 part of tin: the above compounds are those used in the manufacture of small and great brass guns, swivels, etc.
The pieces of ordnance used by the besiegers at the battle of Prague, were actually melted by the frequency of the firing; the mixture of which they were made contained a large portion of lead; it would have been less prone to melt, and consequently preferable, had it contained none. A mixture of copper and tin is preferred to pure copper, not only lor the casting of cannon, but of statues, etc.; for pure copper, in running through the various parts of the mould, would lose so much of its heat as to or become solid too soon. Jlell metal.
Melt together 6 parts of copper, and 2 of tin: These proportions are the roost approved for bells throughout Europe, and in China.
In the union ol the two metals above mentioned, the combination is so complete, that the specific gravity of the alloy is greater than that of the two metals uncombined.
Another.—Some bells are made in the proportion of 10 parts of copper to 3 of tin. It may be in general observed, that a less proportion of tin is used for making church bells, than clock bells; and that a little zinc is added for the bells of repeating watches and other small bells.
Melt together 8 ounces of copper, and £ an ounce of neutral arsenical salt, fused together, undera flux continued of calcined borax, charcoal dust, and tiue powder glass.
Cotiipsntion of ancient ttatne*.
According to Pliny, the metal used by the Romans for thjr statues, and for the platts on which' they engraved inscriptions was composed in the fallowing manner. They first melted a quantity of cupper, into which they put a third of its weight of old copper, which had 1><>cn long in use; to every 100 lbs. weight nf this mixture they added 12^ lbs. ot w\ nUn* composed ol equ*J nun? of lead and tin.
Mock platfna. Melt together 8 ounces of brass and 5 ounces ol
Fine carting of bra*$, £jfc. The principal object in fine casting is to have a mould that shall receive a beautiful impression, and at the same time sufficiently adhesive to resist the force of the fluid metal, that shall neit her wa*h, nor be injured by the heat. The sand that covers or surrounds the model should be fine close sand; after removing the mould, the model must be '"act -d with burnt rotten stone, and covered with loam, each dusted through a bag, and the mould laid down upon it—this facing may be repeated, the mould must be dried and smoked with a torch, in lieu of water, the sand is moistened with a solution of tartar, or the lees of wine, or with cream of tartar. Care must be taken to loosen the bands quickly: viz. loosen the first mould, while the second is pouring, etc. On removing the work, every
Krtiele of Uie lacing should be carefully scraped >m the mould and thrown away. Part the moulds with coal and black rosin.
Gilding metal Melt together 4 parts of copper, 1 of Bristol old brass, and 14 oz. of tin, to every pound of copper. For common jewellery. Melt together 3 parts of copper, 1 of Bristol old brass, and 4 oz. of tin, to every pound of copper.
If this alloy is for fine polishing, the tin may be omitted, and a mixture of lead and antimony substituted. Paler polishing metal is made by reducing the copper to two or to one part.
Yellow dipping metal Melt together 2 parts of Oncadle brass, 1 part ol copper, with a little Bristol old brass, and £ oz. of tin to every pound of copper.
This alloy is almost ol the colour, etc. of gold coin. Cheadle brass is the darkest, and gives the metal a greenish hue. Old Bristol brass is pale and yellow.
Another.—Good dipping metal may be made ot 1 pound of copper to 5 oz. of spelter; the copper should be tough cake, and not tile.
When antimony is used instead of tin, it should be in smaller quantity, or the metal will be brittle. Imitation of tilver.
When copper is melted with tin, about 2 oz. of Cn to a pound of copper, will make a pale bellmetal, tfiey will roll and ring very near to sterling silver.
Tutania or Britannia metal.
Melt together 4 oz. of plate brass, and 4 oz. tin. When in fusion, add 4 oz. bismuth, and 4 oz. regulus of antimony.
This is the hardening, which is to be added ai discretion to melted Uu, until it has the requisite colour and hardness.
Another.—Melt together 2 lbs. of plate brass, 2 lbs. of a mixture if copper and arsenic, either by cementing or melting, 2 lis. of tin, 2 lbs. of bismuth, and 2 lbs. regulus of antimony.
This is to be added at discretion, to melted ti;t
Another.—Melt together 1 lb. of copper, 1 lb. tin, and 2 lbs. regulus of antimoDy, with or without a little bismuth.
Another,—Melt together 8 oz. ShruflT brass, 2 lbs. regulus of antimony, and 10 lbs. tin.
This is fit for use as Britannia metal.
Melt together 2 drachms of copper, 1 oz. of regUus of antimony, and 12 oz. of tiu.
To 8 oz. of scrap iron or steel, at a white heat, add 1 lb. of antimony in small portions, with 3 oc of nitre. Melt and harden 1 lb. ot tin with 2 os of this compound.