Fine Casting of Brass, etc. 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 neither wash 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 faced 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 band quickly, viz. loosen the first mould while the second is pouring, etc. On removing the work every particle of the facing should be carefully scraped from the mould and thrown away. Part the moulds with coal and black rosin. Imitation of Silver. When copper is melted with tin, about oz. of tin to 1 lb. of copper, will make a pale bell-metal; it 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 at discretion to melted tin, until it has the requisite color and hardness. Another.-Melt together 2 lbs. of plate-brass, 2 lbs. of a mixture of copper and arsenic, either by cementing or melting, 2 lbs. of tin, 2 lbs. of bismuth and 2 lbs. regulus of antimony. This is to be added at discretion to melted tin. Another.-Melt together 1 lb. of copper, 1 lb. tin and 2 lbs. regulus of antimony, with or with out a little bismuth. Another.-Melt together 8 oz. Shruff brass, 2 lbs. regulus of antimony and 10 lbs. tin. This is fit for use as Britannia metal. German Tutania. Another.-Melt together 4 oz. of antimony, 1 oz. arsenic, and 2 lbs. tin. This compound is ready for use. The first of these Spanish alloys would be a beautiful metal, if arsenic were added. Engestroom Tutania. Melt together 4 parts copper, 8 parts regulus of antimony, and 1 part bismuth. When added to 100 parts of tin, this compound will be ready for use. Kustitien's Metal for Tinning. To 1 lb. of malleable iron, at a white heat, add 5 oz. regulus of antimony, and 24 lbs. of the purest Molucca tin. This alloy polishes without the blue tint, and is free from lead or arsenic. A New Silver Alloy. M. De Ruolz and De Fontenay, of France, have lately obtained, after several years' experiments, coin and for many industrial uses. It is composed a new alloy, which may be very useful for small of silver, 25 to 30 per cent. of nickel, and from 37 to 50 per cent. of copper. Its inventors propose to call it tiers-argent, or tri-silver. Its preparation is said to be a triumph of metallurgical science. The 3 metals when simply melted together form a compound which is not homogeneous; have been compelled to use phosphorus and cerand to make the compound perfect, its inventors tain solvents which they have not yet specified. The alloy thus obtained is at first very brittle; it cannot be hammered or drawn, and lacks those properties which are essential in malleable metals. But after the phosphorus is eliminated, the alloy perfectly resembles a simple metal, and possesses, Melt together 2 drs. of copper, 1 oz. of regulus in a very high degree, the qualities to which the of antimony and 12 oz. of tin. Spanish Tutania. To 8 oz. of scrap-iron or steel, at a white heat, add 1 lb. of antimony in small portions, with 3 oz. of nitre. Melt and harden 1 lb. of tin with 2 precious metals owe their superiority. In color it resembles platinum, and is susceptible of a very tenacity. It is ductile, 'malleable, very easily high polish. It possesses extreme hardness and fused, emits when struck a beautiful sound, is not affected by exposure to the atmosphere, or to any but the most powerful re-agents. It is without odor. Its specific gravity is a little less than that Melt together 20 parts of copper, 15.8 of nickel, of silver. An alloy possessing these qualities 12.7 of zinc. oz. of this compound. German Silver. must be very useful to gold and silversmiths. It 1 Foils may be made of copper or tin; and silver has been sometimes used, with which it has been advised, for some purposes, to mix gold; but the expense of either is. needless, as copper may be made to answer the same end. can be supplied at a price 40 per cent. less than | much inclined to the blue, or under crimson, where silver, and its greater hardness will give it a mark- it is desired to have the appearance more orange ed superiority. It may also serve as a substitute or scarlet. for gold-plated or silver-plated articles, which are now so common on account of their cheapness, but which will not bear replating more than a few times, and which are, in the long run, sometimes more expensive than the pure metal. The new alloy, however, will be most useful for small coin. Its preparation and coinage are so difficult that the coin made of it cannot easily be counterfeited. Its hardness would render it more durable than silver; and thus the expense of re-coining, and the heavy loss arising from the wearing of our silver coinage, would be greatly diminished. Silver Test. Silver coins, jewelry, or any other rich alloy, when moistened with a solution of chromic acid, or a mixture of bichromate of potassa and sulphuric acid, become covered with a red purple spot of bichromate of silver. This spot does not occur on poor alloys or metals imitating silver. Useful Alloy of Gold with Platinum. Put into a clean crucible 74 drs. of pure gold, and when perfectly melted, throw in a dr. of platinum. The 2 metals will combine intimately, forming an alloy rather whiter than pure gold, but remarkably ductile and elastic; it is also less perishable than pure gold or jewellers' gold; but more readily fusible than that metal. These excellent qualities must render this alloy an object of great interest to workers in metals. For springs, where steel cannot be used, it will prove exceedingly advantageous. It is a curious circumstance, that the alloy of gold and platinum is soluble in nitric acid, which does not act on either of the metals in a separate state. It is remarkable, too, that the alloy has very nearly the color of platinum, even when composed of 11 parts of gold to 1 of the former metal. Ring Gold. Melt together of Spanish copper, 6 dwts. and 12 grs.; fine silver, 3 dwts. and 16 grs., to 1 oz. 5 dwts. of gold coin. Gold from 358 to 408 per oz. Melt together 8 oz. 8 dwts. of Spanish copper, 10 dwts. of fine silver, to 1 oz. of gold coin. Manheim-Gold, or Similor. To Prepare Copper for Foils. Where colored foils are wanted, copper may therefore be best used, and may be prepared for the purpose, by the following means: Take copper plates beaten to a proper thickness, and pass them betwixt a pair of fine steel rollers very close set, and draw them as thin as is possible to retain a proper tenacity. Polish them with very fine whiting, or rotten-stone, till they shine, and have as much brightness as can be given them, and they will then be fit to receive the color. To Whiten Foils. Where the yellow, or rather orange-color of the ground would be injurious to the effect, as in the case of purples, or crimson red, the foils should be whitened, which may be done in the following manner: Take a small quantity of silver and dissolve it in aqua-fortis, and then put bits of copper into the solution, and precipitate the silver; which being done the fluid must be poured off, and fresh water added to it, to wash away all the remainder of the first fluid; after which the silver must be dried, an equal weight of cream of tartar and common salt must then be ground with it, till the whole be reduced to a very fine powder; and with this mixture, the foils, being first slightly moistened, must be rubbed by the finger, or a bit of linen rag, till they be of the degree of whiteness desired; after which, if it appear to be wanted, the polish must be refreshed. The tin foils are only used in the case of colorless stones, where quicksilver is employed; and they may be drawn out by the same rollers, but need not be further polished, as that effect is produced by other means in this case. Foils for Crystals, Pebbles, or Paste, to give the Lustre and Play of Diamonds. The manner of preparing foils, so as to give colorless stones the greatest degree of play and lustre, is by raising so high a polish or smoothness on Melt together 34 oz. of copper, 14 oz. of brass, the surface, as to give them the effect of a mirror, and 15 grs. of pure gold. PREPARATION OF FOILS. Foils are thin plates or leaves of metal that are put under stones, or compositions in imitation of stones, when they are set. The intention of foils is either to increase the lustre or play of the stones, or more generally to improve the color, by giving an additional force to the tinge, whether it be natural or artificial, by that of a ground of the same hue, which the foil is in this case made to be. There are consequently two kinds of foils; the one is colorless, where the effect of giving lustre or play to the stone is produced by the polish of the surface, which makes it act as a mirror, and, by reflecting the light, prevents that deadness which attends the having a duller ground under the stone, and brings it by the double refraction of the light that is caused, nearer to the effect of the diamond. The other is colored with some pigment or stain of the same hue as the stone, or of some other which is intended to modify and change the hue of the stone in some degree; as, where a yellow foil may be put under green, which is too which can only be done, in a perfect manner, by the use of quicksilver, applied in the same general way as in the case of looking-glasses. The method by which it may be best performed is as follows: Take leaves of tin, prepared in the same manner as for silvering looking-glasses, and cut them into small pieces of such size as to cover the surface of the sockets or the stones that are to be set. Lay three of these then, one upon another, and having moistened the inside of the socket with thin gum-water, and suffered it to become again so dry that only a slight stickiness remains, put the three pieces of leaves, lying on each other, into it, and adapt them to the surface in as even a manner as possible. When this is done, heat the socket and fill it with warm quicksilver, which must be suffered to continue in it 3 or 4 minutes, and then gently poured out. The stone must then be thrust into the socket, and closed with it, care having been taken to give such room for it that it may enter without stripping off the tin and quicksilver from any part of the furnace. The work should be well closed round the stone, to prevent the tin and quicksilver contained in the socket from being shaken out by any violence. The lustre of stones set in this manner will con- | amethyst, topaz, vinegar-garnet and eagle-ma. tinue longer than when they are set in the common way, as, the cavity round them being filled, there will be no passage found for moisture, which is so injurious to the wear of stones treated in any other way. This kind of foil likewise gives some lustre to glass or other transparent matter, which has little of itself; but to stones or pastes that have some share of play it gives a most beautiful brilliance. To Color Foils. Two methods have been invented for coloring foils: the one by tingeing the surface of the copper of the color required by means of smoke, the other by staining or painting it with some pigment or other coloring substance. The colors used for painting foils may be tempered with either oil, water rendered duly viscid by gum Arabic, size or varnish. Where deep colors are wanted, oil is most proper, because some pigments become wholly transparent in it, as lake, or Prussian blue; but yellow and green may be better laid on in varnish, as these colors may be had in perfection from a tinge wholly dissolved in spirit of wine, in the same manner as in the case of lacquers, and the most beautiful green is to be produced by distilled verdigris, which is apt to lose its color and turn black with oil. In common cases, however, any of the colors may be, with least trouble, laid on with isinglass size. in the same manner as the glazing colors used in miniature painting. Ruby Colors. For green, where a deep hue is required, the crystals of verdigris, tempered in shellac varnish, should be used, but where the emerald is to be imitated, a little yellow lacquer should be added to bring the color to a truer green, and less verging to the blue. Other Colors. rine, may be very cheaply imitated by transparent white glass or paste, even without foils. This is to be done by tempering the colors above enumerated with turpentine and mastic, and painting the socket in which the counterfeit stone is to be set with the mixture, the socket and stone itself being previously heated. In this case, however, the stone should be immediately set, and the socket closed upon it before the mixture cools and grows hard. The orange lake above menhas a beautiful effect, and was used with great tioned was invented for this purpose, in which it lor it produces is that of the vinegar-garnet, which success by a considerable manufacturer. The coit affords with great brightness. The colors before directed to be used in oil should be extremely well ground in oil of turpentine, and tempered with old nut or poppy-oil; or, if time can be given for the drying, with strong fat oil diluted with spirit of turpentine, which will gain a fine polish of itself. The colors used in varnish should be likewise thoroughly well ground and mixed; and, in the case of the dragon's blood in the seed-lac varnish and the lacquer, the foils should be warmed before laid on the foils with a broad, soft brush, which they are laid out. All the mixtures should be must be passed from one end to the other, and no part should be crossed or twice gone over, or, at least, not till the first coat can be dry; when, if the color do not lie strong enough, a second coat may be given. ELECTRO-METALLURGY. casting of metals by the agency of electricity. Its Galvanoplasty or Electrotype, is the art of cold applications are extensive. It is used to multiply engravings and photographs; to cover the faces of types with harder metal; to deposit gold, silver, and alloys on other metals, etc. The process depassed through a metallic solution properly prepends upon the fact that an electrical current the metal being deposited upon any conducting pared, will cause a decomposition of the solution; body attached to the negative pole (cathode) of a voltaic cell or battery. This is the pole attached to the zinc plate in all cases. The Battery. The term battery is properly applied to several voltaic cells united. Frequently, however, it is used to designate a single cell. The forms usually employed in practice are Smee's, Daniell's, and the nitric acid battery. In order to avoid confusion, the following points must be well understood. In all the batteries named, there are two plates and av exciting fluid. One of these plates is of zinc, waich must be amalgamated by dipping it into weak sulphuric acid and rubbing the surface with mercury; or better still, immersing the whole plate in a bath of mercury. This must be repeated from time to time, when the battery is in use. This zinc plate is alone acted on by the exciting fluid. It is called the positive plate. Attached to it is a binding screw, by which a wire may be connected with the plate. This screw, or the end of the attached wire, is called the pole or electrode. The name of the pole is opposite to that of the plate. The positive pole or anode being attached to the negative plate, and the negative pole or cathode to the positive (zinc) plate. The Decomposing Cell. Usually the liquid to be decomposed (electrolyte) is kept in a separate vessel, and the current conveyed to it by wires. To the anode is usually of the same character The stones of more diluted color, such as the attached a piece of metal as that to be deposited. This is gradually eaten away while the deposition is going on, on the cathode, and the solution thus kept of uniform strength. The current may be regulated by altering the distance between the poles. With the same battery power, the amount of electricity passing will be less as the distance of the poles in the electrolyte is greater. Too powerful a current must be avoided, as it renders the coating brittle and non-adherent. It should not be strong enough to cause bubbles of gas to arise from the object. A large number of objects can be plated by one battery if they are suspended on copper rods, the ends of which are connected with the pole. Smee's Cell Consists of two plates of amalgamated zinc, separated by a piece of baked and varnished wood, and between them a plate of silver having depos ited on it by the electric current finely divided platinum; so as to roughen it and prevent the adhesion of hydrogen. The silver plate is fixed in the wood separating the zinc plates; to the zine and to the silver plates are attached binding screws for the wires. The exciting fluid is dilute sulphuric acid; 1 part of acid to 20 of water, is strong enough. When more intensity is required, several cells are joined by passing wires from the anode of one cell to the cathode of the next. This form of battery is generally preferred on account of its simplicity, constancy, and ease of manage ment. Daniell's Cell. of cyanide of potassium until no further precipitate is formed; but not enough to re-dissolve the precipitate already thrown down. Pour off the supernatant liquid, wash with water, and then re-dissolve the precipitate in cyanide of potassium. The anode should be of silver. Should the solution change on keeping, add a little fresh cyanide. Use a moderate current. An ounce and a half of silver will give to a surface a foot square, a coating as thick as common writing-paper. And since silver is worth $1.25 per ounce, the value of the silver covering a foot square, would be about $1.87. At this rate, a well plated tea-pot or coffeepot is plated at a cost in silver of not more than $1.50 to $2. The other expenses, including labor, would hardly be more than half that amount. To Recover the Silver from a Bath. Add muriatic acid, carefully avoiding the fumes which are given off. Dilute the liquid, decant from the precipitate formed, dry the precipitate, and reduce in a black lead crucible with carbonate of soda. Solution for Gilding. Electro-gilding is done in like manner. The gold is dissolved in nitro-hydrochloric acid, washed with boiling nitric acid, and then digested with calcined magnesia. The gold is deposited in the form of an oxide, which after being washed in boiling nitric acid, is dissolved in cyanide of potassium, in which solution the articles to be plated with gold, after due preparation, are placed. Iron, steel, lead, and some other metals that do not readily receive the gold deposit, require to be first lightly plated with copper, or dipped in a solution of nitrate of siver, 1 part; nitrate of mercury, 1 part; nitric acid (8. g. 1384) 4 parts; water, 120 parts. The positive plate of the battery must be of gold, the other plate of iron or copper. The process is the same as that above described; use a feeble current. In delicate operations, as in copying engraved plates, where great constancy is required, this form of cell is employed. It consists of a plate of amalgamated zinc, one of copper, generally of cylindrical form separated by a cell of porous earthenware (a flower-pot with the hole closed by a cork, makes a very good porous cell). The plates and cell are enclosed in a glass or earthenware vessel; the zinc is excited by dilute sulphuric The popular notion is, that genuine electroacid; the copper is kept immersed in saturated gilding must necessarily add a good deal to the solution of sulphate of copper (blue-stone). The cost of the article plated. This is erroneous. A solution of copper is gradually decomposed; the silver thimble may be so handsomely plated as to copper being deposited in the copper plate. Hence have the appearance of being all gold for 5 cents, there should always be a quantity of crystals of a pencil-case for 20 cents, and a watch-case for 1 the sulphate at the bottom of the cell, and the dollar. An estimate of the relative value of elecsolution should be stirred from time to time; or tro-gilding, as compared with silver-plating, conthe crystals may be suspended in a basket nearsidering the cost of material alone, is about 15 to 1. the top of the solution. Nitric Acid Batteries. To Deposit Brass. Dissolve 5 oz. powdered acetate of copper in When great intensity is required, as in the de-gall. of water, add 1 pt. of solution of au position of copper on iron, and of certain alloys, the decomposition of fused chlorides for the purpose of obtaining certain metals, these batteries are used. In all cases the positive plate is of amalgamated zinc excited by dilute sulphuric acid; which may be as strong as 1 in 10 with 1-10th of nitric acid. This is separated by a porous cell from the negative plate, which may be of platinum (Grove), carbon (Bunsen), or passive iron (Callan). The negative plate is immersed in strong nitric acid. Iron may be rendered passive by dipping it once or twice into strong nítric acid, and then washing with water and carefully drying. nia. To Prepare Articles for Plating. dilute nitric acid to remove oxide. Scour with a hard brush and fine sand. Then having fastened to a wire, dip in strong nitric acid and immerse in the electrolyte as quickly as possible. Solution for Silvering. Add to a solution of nitrate of silver (made by dissolving silver in pure nitric acid), a solution To Copy Medals. Casts of the medals may be made in fusible metal, plaster, wax, etc. In case of a non-metallic mould it must have its face brushed over with A black lead. The metallic mould is to be coated on the back with wax or varnish. The wire is usually attached to the edge by soldering or twisting. A decomposing cell is not necessary. water-tight box is divided by a porous (plaster or leather) partition. On one side is a plate of zino immersed in diluted, 1 to 20, sulphuric acid; on the other a solution, kept saturated, of sulphate of copper. A wire from the zinc is attached to a copper rod, from which the medals are suspended, which consists simply in depositing copper upon dipping into the copper solution. To Bronze Copper Medals. 1. Brown, Moisten the surface, well cleaned, with weak nitric acid, allow it to dry, and apply a gentle heat. 2. Black.-Use, instead of nitric acid, sulphydrate of ammonia or liver of sulphur. 3. Green.Expose in a close box to the fumes of chloride of lime, or to the vapor of acetic or muriatic acid. 4. For bronzing all sorts of fine copper or brass work a weak solution of bichloride of platinum is used. By varying the temperature and color, between a steel gray and deep black may be obtained. To Deposit Copper on Iron. Prepare a solution of cyanide of copper, by dissolving oxide of copper in cyanide of potassium, or by adding cyanide of potassium to a solution of sulphate of copper, and re-dissolving the precipitate formed. Work with a strong battery power. The copper will not deposit unless the current be strong enough to evolve hydrogen at the cathode, which evolution should always be avoided in depositing the other metals. Voltaic Protection of Metals. When two metals are united and exposed to a corrosive agent, which would act unequally upon them if separate, the one which would be most acted on receives most of the force of the corrosion, while the other escapes. Thus iron coated with zine (galvanized iron) will last for years exposed to the atmosphere. Copper points on lightningrods remain bright for a long time, when screwed into a zine ball. Coating Electrotype-plates with Iron. The following has been successfully employed in Coating electrotype deposits with a coating of pure iron, thereby rendering them little inferior to steel-plate engravings as regards durability: Dissolve 1 lb. of sal ammoniac in 1 gall, of rainwater, then add 2 lbs. of neutral acetate of iron; boil the solution in an iron-kettle for 2 hours, replacing the water lost by evaporation; when cold, filter the solution, and keep it in close-covered vats (when not in use) to prevent oxidation. The iron plate used in the decomposition-cell must be of the same surface as the plate to be coated with iron; a Smee's battery, of at least 3 cells, charged with 1 part sulphuric acid, and 60 parts water, being used for the decomposition. To insure success the following rules must be observed: 1st. The plate must be thoroughly freed from any greasy matter by immersing in a solution of caustic soda, then rinsed in clean cold rainwater, after which dip it in dilute acetic acid, and immediately transfer it to the solution of iron; this will insure perfect adhesion between the metals. 2nd. The solution must be filtered previous to use to remove the oxide of iron formed by exposure to the atmosphere. After the plates have been coated with iron they must be well rinsed in clear warm rain-water, then in a weak alkaline solution, well dried with a piece of clean soft cotton, and slightly oiled to prevent oxidation. The coating of iron is very hard and brittle, resembling the white iron used by manufacturers of malleable iron. Should any of the surface be damaged, the whole coating of iron may be removed by immersion in dilute sulphuric acid, and re-coated again by the above process. Copper Tubes made by Galvanic Process. Le Génie Industrial publishes the details of a process for making copper-tubes without soldering, This lead patterns by the galvanic battery, and then melting out the lead. It is said to work perfectly, and of course tubes could be made of any desired form-straight, curved, or right-angled. suggests the idea of forming tubes in the same manner with cores of wax or clay. The clay may be forced into the size of the pipe through a draw. plate, then allowed to harden slightly, when it may be covered with plumbago and an electrodeposit of copper made upon it with a galvanie battery. When the copper is deposited in sufficient thickness the clay may be removed from the interior by boiling the pipe in water. To conduct this manufacture it would require long depositingtroughs, and the expense would probably be too great for making straight copper-tubes; but for curved tubes, such as the worms of stills, it would made by filling straight tubes with hot resin, then perhaps pay. Curved copper-tubes are commonly twisting the entire tube into its curved form When the resin becomes cool it is driven out by striking the pipe, which breaks the resin-core into small pieces. GILDING, SILVERING, AND TINNING. To Gild Glass and Porcelain. Drinking and other glasses are sometimes gilt on their edges. This is done, either by an adhesive varnish, or by heat. The varnish is prepared by dissolving in boiled linseed-oil an equal weight either of copal or amber. This is to be diluted by a proper quantity of oil of turpentine, so as to be applied as thin as possible to the parts of the glas intended to be gilt. When this is done, which will be in about 24 hours, the glass is to be placed in a stove, till it is so warm as almost to burn the varnish will become adhesive, and a piece of leaffingers when handled. At this temperature the gold, applied in the usual way, will immediately stick. Sweep off the superfluous portions of the leaf; and when quite cold it may be burnished, (Indian paper) between the gold and the burnisher. taking care to interpose a piece of very thin paper If the varnish is very good, this is the best method of gilding glass, as the gold is thus fixed on more evenly than in any other way. Another Method. It often happens, when the varnish is but indif. ferent, that by repeated washing the gold wears off; on this account the practice of burning it in is sometimes had recourse to. For this purpose some gold powder is ground with borax, and in this state applied to the clean surface of the glass by a camel's-hair pencil. When quite dry the glass is put into a stove heated to about the temperature of an annealing oven; the gum burns off, and the borax, by vitrefying, cements the gold with great firmness to the glass, after which it may be burnished. The gilding upon porcelain is in like manner fixed by heat and the use of borax; and this kind of ware being neither transparent nor liable to soften, and thus to be injured in its form, in a low red heat, is free from the risk and injury which the finer and more fusible kinds of glass are apt to sustain from such treatment. Porcelain and other wares inay be platinized, silvered, tinned, and bronzed in a similar manner. Preparation for Gilding Porcelain. This preparation, the invention of the brothers Dutuste, is reported on by Salvétat. The peculiar advantage of it is, that after burning the gold is so bright as not to require polishing. Thirty-two grammes of gold are gently warmed with 128 |