SECTION 17.METALLIC ALLOYS.
When two or more metals of different specific gravities are melted together and intimately mixed, they frequently enter into chemical union and form a new compound, called an alloy of the metals. Thesealloys often possess important properties which their constituents singly do not, and hence become valuable acquisitions to the arts. The metals thus combined may be fused together in any proportion; but if one of them greatly exceed the other in specific gravity, their intimate union is sometimes rendered difficult and even impracticable, partly from the weak affinity and partly from the gravitating principle causing the metal of least specific gravity to arise to the surface.
Notwithstanding this union of metals in seemingly indefinite proportions, there are only a few proportions in which the alloys possess peculiar excellences so as to entitle them to the attention of artists. These proportions have in many instances been discovered by experience; and it only remains for theory to point out the reason for such proportions, and to suggest other proportions which may bid fair to possess desirable qualities, and thereby diminish the unsuccessful attempts for improvement in these combinations.
That the metals thus alloyed constitute true chemical compounds and not merely mechanical mixtures, may be inferred from the change made in their primary qualities; such as
1.Tenacity,hardness, &c. Some alloys are much superior to their ingredients in tenacity and hardness, whilst others affect a kind of medium between them. This last is often the case too in regard to ductility and malleability.2.Fusibility.Several alloys fuse at temperatures intermediate between the fusing temperatures of their ingredients, but mostly lower than the mean; there are others which fuse below the temperature of the lowest, and few if any require a temperature above the mean for their fusion.3.Colour.In many cases the colour of alloys is such as would be produced by the mixture of the colours of the metals; but in others, remarkably different; for instance, the alloys of copper and zinc,—forming the various kinds of brass.4.Specific gravity.This is not always what might be inferred from a mixture of the two ingredients. Sometimes it is greater and other times less; but this is not a decisive mark of chemical union, as the same metal varies in specific gravity, by hammering, rolling, tempering, &c. very considerably. Besides, it is more than probable that the differences said to have been observed, have in some instances arisen from inaccurate experiments; as it is a delicate operation to find the specific gravity of small pieces of metal with sufficient precision for comparisons of this kind.
1.Tenacity,hardness, &c. Some alloys are much superior to their ingredients in tenacity and hardness, whilst others affect a kind of medium between them. This last is often the case too in regard to ductility and malleability.
2.Fusibility.Several alloys fuse at temperatures intermediate between the fusing temperatures of their ingredients, but mostly lower than the mean; there are others which fuse below the temperature of the lowest, and few if any require a temperature above the mean for their fusion.
3.Colour.In many cases the colour of alloys is such as would be produced by the mixture of the colours of the metals; but in others, remarkably different; for instance, the alloys of copper and zinc,—forming the various kinds of brass.
4.Specific gravity.This is not always what might be inferred from a mixture of the two ingredients. Sometimes it is greater and other times less; but this is not a decisive mark of chemical union, as the same metal varies in specific gravity, by hammering, rolling, tempering, &c. very considerably. Besides, it is more than probable that the differences said to have been observed, have in some instances arisen from inaccurate experiments; as it is a delicate operation to find the specific gravity of small pieces of metal with sufficient precision for comparisons of this kind.
Many of the simple metals, when fused and exposed to the air for some time, without a covering of charcoal, or some similar principle, acquire less or more of oxygen, and retain it even in a fluid state, as is proved from Mr. Lucas’s interesting communication in the 3d Vol. of the Manchester Society’s Memoirs (new series). Hence by frequent fusions of the same metal its quality becomes impaired in regard to tenuity and other properties.
This is more eminently the case with regard to alloys. Thus, zinc at the temperature in which brass melts is combustible; and hence a portion of it escapes by combustion. Hence the proportions of brass are changed less or more at each fusion, unless fresh zinc be added. The same observation applies to alloys of copper and tin with regard to the tin. The mixtures of lead, tin, bismuth and other soft and easily fused metals, are still more remarkable in this respect. They should be fused under a cover of oil or tallow in order to keep them of the sameproportions; otherwise, some of them, particularly the tin, is liable to great oxidation, and no two successive fusions will present the same alloy. Hence in some degree the use of fluxes in metallurgy which serve to cover the surface of the metals and prevent oxidation from the atmosphere.
When an alloy is made, it seldom happens that the metal is perfect and compact the first fusion; it is more or less porous, especially when the two metals fuse at very different temperatures. By a second fusion, which usually takes place at a much lower temperature than that requisite for the first, the metal becomes compact and free from pores. This is particularly the case with speculum metal; and I have little doubt it is so with regard to many other alloys.
Gold unites with many of the metals by heat, and forms various alloys, on which it may be proper to make a few remarks.
1.Gold with platina.Platina in a small proportion changes the colour of gold towards white. 1 part to 20 gold makes it much paler. 1to 11 gives it the colour of tarnished silver. 1 part with 4 of gold has much the appearance of platina. The colour of gold does not predominate till it becomes ⁸/₉ of the alloy. The alloy of 1 platina and 11 gold is very ductile, and elastic when hammered.Lewis. Klaproth. Vauquelin.
2.Gold with silver.These two metals may be combined in almost any proportion by fusion and proper treatment. Homberg found that when equal parts of gold and silver are kept in fusion for a quarter of an hour and then cooled, there were two masses, the uppermost pure silver, the undermost an alloy of 5 parts gold and 1 silver. 1 part silver to 20 gold produces a sensible whiteness in the alloy. 2 parts gold and 1 of silver are stated to form the alloy of greatest hardness; this will consist of 3 atoms of gold to 1 of silver.
3.Gold with mercury.See amalgams.
4.Gold with copper.Gold and copper form an alloy by fusion together. 11 parts gold and 1 copper form the alloy used for gold coin. The copper heightens the colour of the gold, and makes it harder and less liable to wear. The current gold coin, however, usually contains both silver and copper, but the weight of both does not much exceed onetwelfth of the whole. According to Muschenbroeck the maximum of hardness is when 7 parts of gold and 1 part of copper are united. This corresponds nearly to 6 atoms of gold and 1 of copper, the atom of gold being estimated at 66 and that of copper at 56.
Other alloys of gold besides the above standard is that for watch cases, which must contain at least ¾ pure gold. Watch chains, and trinkets, are usually made of inferior alloy, called jewellers gold, which is under no control. It rarely contains less than 30 per cent. of pure gold.
5.Gold with iron.Gold and iron may be united by fusion in various proportions. 11 parts gold and 1 iron form a ductile alloy which may be rolled and stamped into coin. Its specific gravity is 16.885. The colour is a pale yellowish gray approaching to white. The alloy is harder than gold. When the iron is three or four times the weight of gold, the alloy has the colour of silver. This last compound is constituted of 1 atom of gold and 8 of iron nearly.Lewis. Hatchett.
6.Gold with nickel.Mr. Hatchett fused 11 parts gold and 1 nickel together, and obtained a brittle alloy of the colour of fine brass.
7.Gold with tin.Gold combines with tin and forms a brittle alloy. 10 parts gold and 1 tin form a pale alloy and less ductile than gold. One fiftieth of tin does not materially injure the ductility. Heat, up to a visible red, does not impair the alloy; but beyond that the tin fuses and the alloy falls to pieces.Hatchett.
8.Gold with lead.The effect of uniting even a very small proportion of lead to gold is remarkable. When the alloy contains ¹/₂₀₀₀ part of lead, it is brittle like glass. The vapour of fused lead in close vessels is sufficient to injure gold.ibid.
9.Gold and zinc.These two metals combine in almost any proportion. When 11 parts gold and 1 zinc are alloyed, the compound is of a pale greenish yellow like brass, and very brittle. Equal parts of these metals form a very hard, white alloy, susceptible of a fine polish.ibid.&Hellot.
10.Gold and bismuth.Gold unites with bismuth, but the colour is injured and the ductility of the alloy destroyed by a very small portion of the latter metal, the same as with lead.ibid.
11.Gold and antimony.These metals combine and produce a brittle alloy, much of the same kind as those with bismuth and lead.ibid.
12.Gold and arsenic.There seems a considerable affinity between gold and arsenic, but the volatility of arsenic in the fusing temperature of gold renders it difficult to bring them into contact. A very small proportion of arsenic makes the alloy brittle, and this property increases with the arsenic.Hatchett.
13.Gold with cobalt.These unite and form a brittle alloy, even when the cobalt only makes ¹/₆₀ of the compound.ibid.
14.Gold and manganese.Gold and manganese may be united, and the alloy is very hard and less fusible than gold. One alloy was found to consist of 7 or 8 parts of gold and 1 of manganese.ibid.
1.Platina and silver.It does not appear very clear that these two metals combine by fusion; at least if they do, the difference in their specific gravities is sufficient to overcome their affinity.
2.Platina and mercury.See amalgams.
3.Platina and copper.These two metals unite with difficulty by a strong heat and form a malleable alloy. This alloy has been preferredfor specula for telescopes, as it is hard, polishes well, and is not liable to tarnish.Lewis.
4.Platina and iron.Platina and soft or pure iron do not seem to be easily combined by heat, by reason of the infusibility of iron. But it combines with cast iron and steel by heat. The alloy is very hard, and in some decree ductile when the iron forms ¾ of the alloy.ibid.
5.Platina and tin.Equal parts of platina and tin unite by fusion, and form a dark coloured brittle alloy. But when the platina falls short ⁷/₉ of the alloy, the ductility and whiteness proportionally increase.ibid.
6.Platina and lead.These two metals may be combined in various proportions by heat; but the compounds are not stable, part of the platina falling down, when the alloy is subsequently melted.ibid.
7.Platina and zinc.Platina may be combined with zinc, by being exposed to the fumes of the metal as reduced from its ore. Three parts of platina become four of alloy. It is hard, brittle, of a blueish white colour, and easily fusible.ibid.
8.Platina and bismuth.Platina and bismuth combine readily in a high temperature in almost any proportions. The alloys are brittle.ibid.
9.Platina and antimony.Platina easily combines with antimony by heat. The alloy is brittle.ibid.
10.Platina and arsenic.When white oxide of arsenic is projected upon strongly heated platina, an imperfect union takes place with a partial fusion of the mass; it is brittle, of a greyish colour and a loose granulated texture.Lewis.
1.Silver with mercury.See amalgams.
2.Silver with copper.Silver and copper are easily alloyed in any proportion by fusion. The compound is harder than silver, and retains its white colour when the copper is half of the alloy or more.—The silver coin is a compound of 12⅓ silver and 1 copper, which nearly corresponds to 8 atoms of silver and 1 of copper. The hardest alloy is said to be when 5 silver unite to 1 copper; that is, 3 atoms of silver and 1 of copper.
3.Silver with iron.The alloys of silver and iron have not been very minutely examined. The two metals are said to unite by fusion, but the iron still retains its magnetism. The alloy is of a white colour,hard and ductile. When kept in fusion for some time the two metals separate, but not entirely. These circumstances shew the affinity between silver and iron to be weak.
4.Silver with tin.Silver and tin form a hard brittle alloy, which is of little if any use. The modifications arising from various proportions have not been particularly investigated.
5.Silver and lead.Silver and lead unite in any proportion and form a brittle alloy of a lead colour. The union is not very intimate; for when urged by heat the lead parts from the silver, as in the process of cupellation.
6.Silver and zinc.These two unite and form a brittle alloy of a blueish white colour. The proportions have not been particularly noticed.
7.Silver and bismuth.Silver and bismuth readily unite by heat. The alloy is brittle and its colour inclines to that of bismuth.
8.Silver and antimony.These metals unite by fusion and form a brittle alloy, which does not seem possessed of any remarkable properties.
9.Silver and arsenic.These two metals unite according to Bergman, the fused silver taking up ¹/₁₄ of its weight of arsenic; thealloy corresponds nearly to 3 atoms silver and 1 arsenic. It is brittle and of a yellowish colour.
The alloys of Mercury with the various metals have been commonly denominated amalgams.
1.Mercury and gold.Gold amalgamates pretty easily with mercury and forms an alloy much used in gilding metals. For this purpose six parts of mercury may be heated nearly to the ebullition of the liquid, and one part of pure gold in thin plates may be gradually added. In a few minutes the whole becomes one fluid mass of a yellowish white colour. It is constituted of 1 atom of gold and 2 of mercury. By squeezing it through leather one half of the mercury is separated nearly pure, and the other remains combined with the gold, and forms a soft white mass, consisting of 1 part gold and 2½ mercury nearly, which is the alloy of 1 atom to 1, and may be subsequently used for gilding. A ready way of making this amalgam I find is to put 3 parts of gold,precipitated by green sulphate of iron, to 8½ or 9 parts of mercury; by a few minutes trituration the whole becomes a fine crystalline amalgam.—When this amalgam of gold is exposed to a heat just below red, the mercury sublimes and leaves the gold; hence its use in gilding.
2.Mercury and platina.These two metals may be combined, but not very easily, as little affinity seems to exist betwixt them. This is manifest from the circumstance that platina wire may be long immersed in mercury without any sensible effect. An union may be produced by immersing thin platina foil into boiling mercury for some time; also by triturating the ammonio-muriate of platina with mercury and exposing it to a due heat. The proportions have not been determined.
3.Mercury and silver.Silver and mercury have a considerable affinity and are easily combined by putting lamina of silver into heated mercury and agitating the mixture. When 1 part silver and 2 mercury are mixed as above, a fluid mass is obtained which being heated to the temperature of boiling mercury, a little mercury evaporates and the remainder crystallizes into a soft white mass, which in time growshard and brittle. A higher heat than boiling mercury expels the mercury. Hence this amalgam may be used for giving a thin coating of silver to the surface of metals, like that of gold. The compound is evidently one atom of silver (90) with one of mercury (167).
4.Mercury and copper.I have made several unsuccessful attempts to combine mercury and copper.
When a plate of copper is kept immersed in mercury for some time, the mercury adheres to its surface in a small degree and is not easily rubbed off; the plate is rendered brittle by it and the fracture has a brilliant mercurial appearance; but a low red heat expels the mercury and the copper resumes its colour and tenacity, with scarcely any loss of weight, being only about 5½ per cent. in two or three trials.
Recently precipitated copper in powder, dried and triturated with mercury, produced no union. Neither did Dutch-leaf (which is copper with a very little zinc) unite with mercury by trituration. Mercury precipitated from deutonitrate by a plate of copper gave pure running liquid. The plate of copper appeared as if it had been immersed inmercury, was brittle with a shining fracture, but recovered its colour and texture by heat, and lost scarcely any weight.
The method recommended by Boyle was tried: 2½ parts of crystallized verdigris, 2 parts of mercury and 1 of common salt, were triturated together till the mercury disappeared, the powder was then digested awhile with vinegar over a fire and frequently stirred. The mass was then put on a filter and dried. It contained a little fluid mercury, but was chiefly composed of acetate of copper and oxide or muriate of mercury. The liquid contained acetate of copper and muriate of soda.
From the above it is manifest that mercury has some chemical action upon copper; but it has not yet been found, I apprehend, that the two metals unite so as to form a proper amalgam.
5.Mercury and iron.These two metals have little if any affinity for each other. I do not know that any chemical combination of them has ever been formed.
6.Mercury and tin.These two metals readily combine, especially if assisted by heat. I heated 52 parts of tin and 167 of mercury together, that is, 1 atom of each, till they united in a fluid mass.The amalgam crystallized in about 180°. By hard pressure in the hand nearly 50 parts of fluid mercury were separated from the amalgam when cool, containing in appearance very little tin. After this an amalgam was formed of 104 parts of tin and 167 mercury (2 atoms tin to 1 mercury); this congealed about 230°, and remained a hard, dry, crystalline substance, agreeing in appearance with that which adheres to mirrors. For the purpose of silvering mirrors however much more mercury is employed than is indicated by the above proportion; but after the glass is slid upon the tinfoil previously covered with mercury, a great pressure is applied, which expels the superfluous mercury nearly in a state of purity.
7.Mercury and lead.To 90 parts of lead I put 167 of mercury (1 atom of each); they united in a moderate heat and crystallized in about 180°. In a few days the mercury partly separated from the amalgam, and 56 parts were squeezed out, the whole was then put together with 90 parts more of lead (now 2 atoms lead to 1 mercury), and fused together; the amalgam crystallized in about 200°, and remained in a solid uniform mass.
8.Mercury and zinc.When 29 parts zinc and 167 mercury (1 atom to 1) are heated together, they combine and form an amalgam whichcrystallizes about 200°. A little of the mercury may be squeezed out when cold. By putting 29 parts more of zinc (2 atoms to 1) we obtain an amalgam which fuses considerably above 200°, and when cooled becomes a permanent hard crystalline mass.
9.Mercury and bismuth.When 62 parts bismuth are fused with 167 mercury (1 atom to 1), the compound remains fluid at common temperature, but crystallizes partially by standing; about ⅓ of the weight may be poured off like fluid mercury. If we put 62 bismuth more to the whole (so as to be 2 atoms to 1), the fluid amalgam crystallizes about 150 or 180°: the mass is soft however and by pressure one may squeeze out about 20 per cent. of a fluid amalgam. If we put 62 more bismuth (so as to be 3 atoms to 1), then the compound crystallizes between 200 and 300° into a darkish coloured granular soft mass which continues without any change. Higher than this of bismuth I have not examined.
10.Mercury and antimony.Antimony is said to form a feeble union with mercury, which is soon loosened by time. I made several unsuccessful trials to combine these two metals, which it seems unnecessary to detail, as the compound when formed is no ways interesting.
11.Mercury and arsenic.On the authority of Lewis an amalgam of mercury and arsenic may be made by keeping them over the fire for some time and constantly agitating the mixture. It is grey-coloured, and composed of 5 parts of mercury and 1 of arsenic.
Most of the other metals are incapable, as far as is known, of combination with mercury, excepting potassium and sodium considered as metals, which combine with mercury; but these alloys are of little interest, and the proportions have not been particularly investigated.
Besides those amalgams which are formed of mercury and each single metal, there are others formed of mercury and alloys of two or more metals, which in some instances possess properties differing essentially from mere mixtures.
1.Mercury with bismuth and lead.When the amalgam formed of 2 atoms bismuth and 1 of mercury is mixed with that formed by 1 atom oflead and 1 of mercury, in such proportion that the mercury is the same in both, the two powders, though dry and crystalline at first, soon become a permanently fluid amalgam by trituration. The liquid in running alongdrags a tail after it, and is disposed to separate into portions less and more fluid, but the most fluid part is much inferior to pure mercury in this respect. Specific gravity of the amalgam, 11.
2.Mercury with fusible metal composed of 7 bismuth, 5 lead and 3 tin.A mixture of 4 parts fusible metal with 5 parts mercury compose the most fusible amalgam with a minimum of mercury that I have found. It is formed of 2 atoms bismuth, 1 lead, 1 tin and 2 mercury. Its specific gravity is 12.
3.Mercury, zinc and tin.This amalgam is found the most effectual for the excitation of electric machines. Mr. Cuthbertson recommends 1 part zinc, 1 tin and 2 of mercury for the plate machine amalgam. But for a cylinder the best amalgam I have made contains more than twice the above portion of mercury. I form an alloy of 58 parts zinc and 52 tin, (2 atoms to 1). To this alloy I add 250 mercury, and fuse the mixture; the liquid mass crystallizes about 222° into a white, moderately hard amalgam. This is pulverized in a mortar and mixed upwith ¹/₁₂ of its weight of hog’s lard. A small portion then is spread upon a piece of leather and applied to the machine when in action. It is probable however that a harder and less unctuous amalgam may be better adapted to the plate machine. This amalgam of mine consists of 4 atoms of zinc, 2 of tin and 3 of mercury.
I have tried the amalgams of zinc and tin separately and find that they answer for electric excitation as well as when combined. They ought to be formed of 2 atoms zinc and 1 of mercury (58 parts to 167), and of 2 atoms tin and 1 of mercury (104 parts to 167). If we choose to combine them, we have only to take 2 parts of the zinc amalgam and 1 of the tin amalgam and triturate them together.
Bismuth amalgam is not good for electric excitation; lead amalgam is better; but they are much inferior to those of tin and zinc.
1.Copper and iron.These two metals may be united with difficulty by heat; but the compound possesses no useful property.
2.Copper and nickel.A white, hard, brittle alloy is said to be formed by combining these two metals. The alloy is scarcely known.
3.Copper and tin.The metals of copper and tin, may be fused together and united in almost any proportion by skilful treatment; but it is found that only a few of the proportions constitute alloys possessing properties eminently valuable to the arts.
The alloys of copper and tin are commonly calledbell-metal; but they receive more particular names according to the purposes for which they are destined, asbronze,speculum metal,gun-metal, &c. those of them which are yellow are frequently confounded in common language with brass, asbrass guns, &c. Indeed the ancient Greeks and Romans seem to have been in possession of these two alloys, under one and the same name. Theχαλκοςof the Greeks, being used for cutting-instruments, must have signifiedbell-metal, or the alloy of copper and tin as well as brass, as indeed is proved by the analysis of them. Theæsof the Romans seems also to have included the same compound. Ancient copper coins too are usually found to contain tin.
Tin united to copper in certain proportions gives a surprising degreeof hardness and tenacity to the alloy, much superior in these respects to either of the ingredients. In other proportions it makes the compound highly sonorous, as inbell-metalproperly so called. Tin also increases the fusibility of the compound in proportion as it abounds, being itself fusible at the low temperature of 440° Fahrenheit.
The principal varieties in the alloys of copper and tin are enumerated below, beginning with those in which the copper is most abundant. The atom of copper is taken at 56 and that of tin at 52 weight, the hardness of these metals is denoted by 7.5 and 6 respectively, by Kirwan.
(a).Gun-metal.The alloy for brass guns or cannon is made of 100 parts of copper and 11 or 12 of tin. A small portion of iron is found to improve the metal; this is best added in the state of tin-plate, as it more readily fuses and unites with the metal.[20]This compound is hard and extremely tenacious, exceeding in this respect anyother alloy of the two metals. The addition or subtraction of 1 or 2 parts of tin materially impairs the tenacity of the alloy. It is constituted of 8 atoms of copper and 1 of tin.
(b).Alloy for edge tools, printers’ cylinders, &c.The best proportion for this compound seems to be 100 parts copper and 15 or 16 tin. When hammered and tempered duly it is fit for making edge tools not inferior to some kinds of steel. It is a compound of greater density than the preceding, though containing more tin; the grain is fine and the metal free from blisters and suited for turning in the lathe. It seems to be the best alloy of the kind for printers’ cylinders; but an analysis which I lately made of some turnings from one of these cylinders gave me much less tin than the above proportion. The alloy (b) is constituted of 6 atoms of copper and 1 of tin.
(c).Alloy for the Chinese gong, cymbals, &c.An alloy formed of 100 parts copper and 23 tin, appears from Dussaussoy’s experiments to form the compound of minimum density. It is used for making cymbals; and nearly accords with the composition of the Chinese gong. It is formed of 4 atoms of copper and 1 of tin. The Chinese gonganalysed by Klaproth was composed of 100 copper and 28.2 tin; that by Dr. Thomson of 100 copper and 23.4 tin.
(d).Common bell-metal used for casting bells.This alloy is commonly made of 3 parts copper and 1 of tin; but to be in due proportion for 3 atoms of copper and 1 of tin, it should be formed of 100 copper and 31 tin. It is hard, of a white colour, less malleable than the preceding alloys, and more sonorous. A specimen I analysed consisted of 100 copper and 36 tin. The exact proportion of 100 copper and 31 tin is not essential to produce a sonorous alloy.
(e).Speculum metal.This compound has been investigated with great care by opticians. According to Mr. Mudge the best proportion is 32 parts copper to 14.5 tin, but Mr. Edwards finds 15 parts tin, 1 brass, 1 silver and 1 arsenic. The slightest variation in the proportions of copper and tin impairs the metal. The alloy is white, hard and close grained; it takes a beautiful polish. The use of the minute portions of zinc, silver and arsenic is perhaps to correct the colour of the alloy; though it seems in several alloys that very minute portions of metals apparently foreign to the alloy, improve the density and texture of the metal. It is remarkable with what precisionthis alloy accords with the atomic combinations of 2 copper with 1 tin. By calculation 32 copper would require 14.8 tin. Mr. Mudge finds 32 copper to 14½ tin, and observes that if ½ a part more of tin be added the metal is too hard. Mr. Edwards indeed says 32 copper and 15 tin; but then he adds 1 part brass, which containing ⅔ of a part of copper, it reduces his proportion to 32 copper and 14.7 tin, almost exactly that required by the theory. When 32 copper and 13½ tin are combined, Mr. Mudge asserts the metal is too soft.[21]
(f).Copper and tin, equal parts.This alloy is of blueish white colour, and of no particular use that I am acquainted with. It consists of the union of 1 atom of copper with 1 of tin.
The other alloys of copper with a higher proportion of tin appear to be uninteresting, and have not been objects of much attention.
Not having an opportunity of forming these alloys synthetically, I contented myself with the analysis of several of them.
The mode of analysis I adopted with compounds of copper and tin, is simple and easy. The alloy is treated with nitric acid, which dissolves the copper, and on being diluted with water throws down the tin in the state of deutoxide. This last is collected on a filtre, dried, and heated to a low red; then ²⁶/₃₃ of this is allowed for the tin (the other 7 parts being oxygen); and the rest of the alloy may be considered as copper. But if thought proper the copper may be thrown down by immersing a plate of lead in the solution, which succeeds better than a plate of iron in nitric solutions of copper.
4.Copper and lead.Copper unites with boiling lead and forms a grey brittle alloy of granular texture. This alloy being heated above the melting point of lead, causes the last metal to run off, leaving the copper nearly pure. The alloy is scarcely of any use.
5.Copper and zinc.Copper and zinc combined formbrass, one of the most useful of all alloys. Though this is a general name for such combinations, yet several of the proportions form compounds to which peculiar names are given, some of which will be noticed below.
It may be proper to remark that copper is estimated by Mr. Kirwan at 7½° in hardness, whilst zinc is 6½. The former metal is highly tenacious and malleable; the latter is brittle and malleable only in a small degree. According to Lewis a very small proportion of zinc dilutes the colour of copper and renders it pale; when the copper has imbibed ¹/₁₂ of its weight, the colour inclines to yellow. The yellowness increases with the zinc till the weight of that metal in the alloy equals the copper. Beyond this point if the zinc be increased the alloy becomes paler and paler and at last white, like zinc.
The tenacity of brass is greater than that of either copper or zinc according to Muschenbroek. His experiments give brass nearly twice as strong as copper, and 18 times as strong as zinc. It seems to me most probable that the tenacity of brass increases with the increase of zinc in the alloy to a certain proportion, when it becomes a maximum, and thence diminishes with the further increase of zinc, but experiments are yet wanting, I presume, to ascertain what proportion of the two metals must be taken to form the alloy of greatest tenacity. The same observation may be made as to the maximum hardness; it is not improbable that the two maxima may be found in different kinds of brass.
The point of temperature at which copper fuses is stated to be 27° of Wedgwood’s thermometer, whilst that of zinc is much lower, namely, 680° of Fahrenheit. Common brass is stated to melt at 21° of Wedgwood. It is very probable that all kinds of brass melt at temperatures intermediate between those of copper and zinc; and that the more of zinc the lower will be the fusing temperature; but there have not been direct experiments to ascertain the degrees, as far as I know.
In enumerating the different proportions of such alloys as have come under my notice I shall begin with that containing the maximum of copper, and proceed in gradation to that with the maximum of zinc.
(a).Brass for the manufacture of plated goods.This alloy is composed, judging from one specimen I analysed, of 12 atoms of copper and 1 of zinc; or of nearly 28 parts of copper by weight and 1 of zinc. The atom of copper is here estimated at 56 and that of zinc at 29, or very nearly ½ that of copper. This alloy had much the same qualities apparently as copper itself, only a little more yellow.
(b).Dutch gold, gilding metal.This is the alloy whichmay be beaten out into thin leaves, after the manner of gold leaf. I have not been able to find any proportions for this compound in books. It seems to have been kept as a secret by the manufacturers. By analysis however I find it composed of 6 atoms of copper and 1 of zinc, or nearly 12 parts copper and 1 zinc by weight. This alloy is probably the most malleable of all the kinds of brass. A leaf containing 12 square inches weighs about ⁷/₁₀ of a grain. The colour, as is well known, makes a good approach to that of gold. It is the composition used for making articles to be gilt, as buttons, &c.
(c).Dipping metal for stamped brass goods.This is a well known article of Birmingham manufacture. It is an alloy both tenacious and malleable, as is manifest from the perfection of the articles. It possesses a beautiful gold colour. A specimen was composed, by my analysis, of 4 atoms of copper to 1 of zinc; or of 8 lbs. of copper and 1 of zinc; or of 4 lbs. copper and 3 of common brass; but it is varied according to the colour wanted.
(d).Soft, fine coloured brass.According to M. Sage, a very fine kind of brass may be made by mixing oxide of copper, calamine, black-flux and charcoal powder together and fusing themixture in a crucible till the blue flame disappears. The brass is found to weigh ⅙ more than the copper resulting from the weight of oxide. He says when the copper retains ⅕ of zinc the colour is not so fine; and the excess of zinc will be burned off by heat, but the zinc cannot be reduced by burning below ⅙; so that this appears to be a natural limit. Hence this compound, being formed of 6 parts copper and 1 of zinc, must be constituted of 3 atoms of copper and 1 of zinc.
(e).Soft brass preferred for watch movements.There is a kind of brass greatly preferred by watch-makers on account of its working well with steel. I have not met with a specimen; but Dr. Thomson has analysed one and found it to consist of 2 atoms of copper and 1 of zinc;[22]or 4 parts copper and 1 of zinc by weight nearly.
(f).Common hard brass.This constitutes the great bulk of brass, as manufactured in the large way. It is made by exposing granulated copper, calamine, that is, a native oxide of zinc, and powdered charcoal in mixture to a red heat for some hours, and thenincreasing the heat so as to melt the compound of copper and zinc, the charcoal having carried away the oxygen of the calamine. The metal is then cast into ingots or plates as may be required. This is called brass of cementation as distinguished from the other species, which are usually made from this by fusion with copper or zinc as the case requires.
It is found that 40lbs. of copper with 60lbs. of calamine yield 60 lbs. of brass; hence a great part of the zinc burns away during the process. The brass thus resulting, consisting of 2 parts of copper and 1 of zinc, is of course constituted of 1 atom of each metal united together.
Common brass is malleable, when cold, like the preceding species; but probably does not possess that property in so high a degree. It seems better adapted for turning in the lathe than any other kind of brass. The specific gravity of this brass before it is hammered or rolled is generally about 8.1 or 8.2 by my experience. When rolled it receives a great increase of density, amounting to .5 according to M. Dussaussoy[23], so that what is 8.2 when cast will be 8.7 when rolled; orit is condensed nearly ¹/₁₆ of its volume by the operation of rolling. The same author finds that brass is hardened very considerably by rolling, but rendered less tenacious; however by being heated and consequently softened after rolling, it becomes stronger than ever, and nearly of an intermediate specific gravity between cast and rolled brass.
(g).Prince’s metal, pinchbeck, &c. This compound, as far as I can learn, is usually formed by combining equal weights of copper and zinc, or by fusing together 3 parts of common brass with 1 of zinc. According to Lewis the yellow colour of brass is a maximum in this proportion. The alloy is brittle, or at least much less malleable than common brass. I find the composition ofspeltersolder, as it is called, or that used for soldering both brass and copper, to be nearly equal parts of copper and zinc. Hence it appears that 1 atom of copper unites to 2 of zinc to form this alloy.
The other alloys of copper and zinc in which the zincgradually exceeds the copper, become gradually paler in colour and more brittle. They do not promise to be of much utility in the arts, and have not therefore been very particularly investigated by metallurgists.
Besides the binary combinations of copper and zinc and copper and tin, there areternarycombinations of these metals, namely, alloys of copper, zinc and tin. For instance, the metal of which common white buttons are made. I had occasion to analyse a specimen of this metal and found it to be constituted of 4 parts copper, 1 of zinc and 1 of tin; or 4 atoms of copper, 2 of zinc and 1 of tin.
It will be proper to subjoin the methods of analysis which I adopted in regard to brass. Twenty grains, more or less, of the particular articles were dissolved in nitric acid, and the metals were precipitated in the state of sulphurets by hydrosulphuret of lime. The copper is thrown down in the state of a black powder, and the zinc in that of a white powder turning to grey. Great care was taken to add the precipitating liquor gradually in order that the copper might beobtained distinctly from the zinc. The whole of the copper is thus thrown down before any of the zinc precipitate appears. The precipitates were collected and dried in a temperature not exceeding 150°, and then weighed. In both cases one third of the weight was allowed for sulphur, and the remaining two thirds were estimated to be metal; which is agreeable to the known constitutions of these sulphurets. Another method I sometimes practised, which also answers very well; namely, to throw down the whole or greatest part of the copper by a plate of lead, then to throw down the lead by sulphuric acid; after this the liquor was tested by hydrosulphuret of lime to precipitate the copper remaining, if any; and lastly to throw down the zinc by hydrosulphuret of lime.
6.Copper and bismuth.The alloy is brittle and of a pale colour. It is not much known.
7.Copper with antimony.Copper and antimony unite by fusion and form a violet coloured, brittle alloy.
8.Copper and arsenic.These metals unite by fusion in a close crucible, the surface of the mixture being covered with common salt to prevent the oxidizement of the arsenic. The alloy is white and brittle,and is known by the names ofwhite copper, andwhite tombac.
9.Copper and manganese.These may be united by fusion, and form a red coloured, malleable alloy, according to Bergman.
10.Copper and molybdenum.These metals may be alloyed in various proportions, but the compounds exhibit nothing peculiarly remarkable.
1.Iron with tin.These two metals are alloyed with some difficulty by fusion in a close crucible. The difficulty seems to arise from the very unequal temperatures at which the metals individually fuse. Bergman always found two alloys when the metals were fused together; the one composed of 21 parts tin and 1 of iron, that is, 10 atoms of tin to 1 of iron; and the other of 2 parts iron, and 1 of tin; that is, 4 atoms of iron and 1 of tin. The first was very malleable, harder than tin and not so brilliant; the second but moderately malleable and too hard to yield to the knife.
The formation of commontin-plateis a proof of the affinity of tin and iron. Thin plates of iron, thoroughly cleaned, are dipped into melted tin, when the tin adheres to the surface of the iron, forming with that metal a true chemical union.
2.Iron and lead, &c. Iron combines by fusion more or less perfectly with lead, zinc, bismuth, antimony, arsenic, cobalt, manganese, &c. but the proportions have in few instances been ascertained, and the compounds are generally of little importance.
Nickel and arsenic.As nickel and arsenic are naturally found in combination, though mostly along with small quantities of other bodies, it is to be presumed that an affinity subsists between them; but I do not know that the proportions have been ascertained in which they unite, or the nature of the alloys.
1.Tin with lead.Tin and lead unite by fusion in any proportion. This alloy, according to Muschenbroek, is harder and muchmore tenacious than either tin or lead, especially when 3 parts tin and 1 lead are its constituents.
I fused various proportions of tin and lead together, as per the following table, in order to find some of the more prominent characteristics of the several alloys. The specific gravity of the tin was 7.2, that of the lead was 11.23; and the portions taken were such as to combine, 1, 2, or more atoms of tin with 1 of lead. The several metals were melted and the compounds formed under a few drops of tallow, otherwise the oxidation is so rapid that the proportions are disturbed and the quantity of pure alloy is not equal to the weight of the ingredients. Without this precaution it is no uncommon occurrence in small experiments to obtain only 3 parts of fusible alloy from 4 of metal.
From the above table it appears that when 1 atom of tin is united to 1of lead there is an expansion of volume; but when more than 1 of tin are combined to 1 of lead there is a contraction of volume, or the density is above that by calculation. This increase of density is greatest when 3 atoms of tin are combined with 1 of lead; and it is not improbable the tenacity may then be a maximum; though Muschenbroek finds it more tenacious when 3 parts tin are united to 1 of lead, which answers more nearly to 4 atoms tin and 1 of lead; this opinion is countenanced by the fact that tin is much the most tenacious of the two metals taken singly.
It is remarkable that the fusing point of these alloys is below those of either tin or lead. The lowest of all (340°) is when 3 atoms of tin are alloyed with 1 of lead.
Common pewter, I find, is an alloy of 4 atoms of tin and 1 of lead nearly, and fuses about 345 or 350°. This is perhaps the best proportion; it is hard, tenacious and of a good colour. More of lead would impair the colour, and more of tin would impair the tenacity and increase the expence, though it might improve the colour.
Certain articles for family use, such as tea-pots, spoons, &c. are made of white metal, which commonly, though I apprehend improperly, goes by the name oftutenag. This metal in colour approaches more tosilver than pewter does. A spoon of this description I found to be pure tin.
2.Tin and zinc.This alloy is easily made by fusion. The metals seem to unite in any proportion. I melted together 29 parts zinc and 52 tin (1 atom of each), and obtained a white hard alloy of about 6.8 specific gravity. When 2 atoms tin and 1 zinc are united the specific gravity is 6.77, which is below the mean. The alloy appears to be very hard and tenacious; and probably might be put to some use.
3.Tin and bismuth.These metals readily combine by fusion in any proportion. When 52 parts tin and 62 bismuth are fused together (1 atom to 1), a fine, smooth, hard but brittle alloy is obtained of the specific gravity 8.42. It fuses at 260°. Two atoms tin and 1 bismuth give an alloy of 8 specific gravity, which fuses about 320°. The alloy of 1 atom tin and 2 of bismuth is of 8.67 specific gravity, and fuses about 260°. The alloy of 3 atoms tin and 1 bismuth is of 7.73 specific gravity, and fuses at 350°. The alloy of 1 atom tin and 3 bismuth is of specific gravity 9.14, and fuses at 330°.
4.Tin with antimony.This compound is said to be white andbrittle when formed of equal parts. I did not succeed in uniting the two metals by fusion on a small scale.
5.Tin with arsenic.When 15 parts of tin and 1 of arsenic are fused together the alloy crystallizes in large plates like bismuth, according to Bayen. It is brittle and less fusible than tin. This alloy must be composed of 5 atoms of tin and 1 of arsenic, that is, 312 tin and 21 arsenic.
1.Lead and zinc.These two metals seem to have a weak affinity. They are easily united, or rather mixed, in any proportion by fusion under a little tallow. But however they may be mixed there is a strong tendency to separate again, which no doubt is occasioned in part by their great difference in specific gravity.
I have fused lead and zinc together in various proportions, from 6 parts lead to 1 of zinc, to 1 part lead to 2 of zinc. The compound usually gives a specific gravity rather greater than the mean; but upon being broken the fracture is often like that of zinc in one part andnot so in another; and the analysis of fragments proves that a great difference exists in their composition. Subsequent fusion sometimes improves the combination and at other times the contrary. Six parts lead and 1 of tin gave a compound as nearly uniform as any. It was 11 specific gravity, harder and whiter than lead and had much the appearance of pewter, that is, the alloy of tin and lead.
2.Lead and bismuth.These metals alloy well. Three parts lead and 2 of bismuth unite by fusion and form a tenacious alloy which fuses about 340°. Muschenbroek found it ten times stronger than lead. It grows dark coloured soon by keeping. Its specific gravity by my observation is 10.85, which is rather greater than the mean. It is constituted of 1 atom of each metal, or 62 bismuth to 90 lead.
Three parts lead and 4 bismuth (1 atom lead to 2 bismuth) fuses at 250°. This is the lowest temperature at which any alloy of two metals fuses. With a little tin it makes the triple alloy which fuses lower than any other metallic compound, without mercury, as will be shown in the sequel. The specific gravity of this alloy of lead and bismuth is 10.7, which is greater than the mean.
The alloy of 1 part lead and 2 bismuth (1 atom of lead and 3 bismuth), fuses at 280°, and is of 10.1 specific gravity, or rather less than the mean.
The alloy of three parts lead and 1 bismuth (2 atoms of lead and 1 of bismuth) fuses at 450°. The specific gravity is 11, or rather greater than the mean.
3.Lead and antimony.These two metals combine by fusion in any proportion. The alloy is of a fine grain and is brittle or flexible as the antimony or lead prevails. The principal use of this alloy, I believe, is in the formation of printers’ types. The small types require a harder alloy or one with more antimony; the large types have a greater share of lead as being less expensive. On examination of the different types I find 3 proportions of the alloy principally in use. The smallest types are cast from a mixture which very nearly corresponds with 40 parts of antimony to 90 of lead (or 1 atom to 1). It is hard, has a fracture like steel and is of the specific gravity 9.4 or 9.5 nearly, and fuses about 480 or 500°. The proportions were determined both by analysis and by inference from the specific gravity of the metal.
The middle sized types are made of metal composed of 1 atom of antimonyand 2 of lead, or 40 parts antimony and 180 of lead. This alloy fuses about 450° or 460° and has the specific gravity of 10 nearly.
The largest types or letters of 2 or 3 inches diameter are made of metal composed of 1 atom antimony and 3 of lead, or 40 parts to 270. This alloy also fuses about 450 or 460°, which is a very remarkable fact. Its specific gravity is usually 10.22. After several trials I could not determine whether the fusing point of this or the preceding alloy was lower; and equal parts of the two alloys fused together were liquified at the same temperature of 450 or 460°.
All the intermediate sizes of types appear to be made of one or other of the three preceding proportions or of mixtures of them, the smaller the type the more of antimony being required to give the requisite hardness. The largest types might, I conceive, be made with a much greater proportion of lead.
When 40 antimony and 360 lead (1 atom to 4) are fused together, the melting point is about 470°. The specific gravity was found 10.4, but probably too low from blisters or air bubbles. The alloy was more flexible than the preceding, but brittle with a fine grained fracture.
Forty parts antimony with 450 lead (1 atom to 5) fused at 490°, and gave 11 specific gravity. This alloy bends and breaks with a fine grained fracture.
Forty parts antimony with 540 lead (1 atom to 6) fused at 510°, and gave 10.8 specific gravity, which in all probability was owing to air bubbles. Now the alloy soft and malleable.
4.Lead and arsenic.When lead is fused in contact with the white oxide of arsenic under a film of tallow and stirred frequently, an union of the two metals takes place and the excess of white oxide is partially converted into arsenic and partly driven off, seemingly taking with it a portion of the lead. A considerable portion of the mass assumes the form of a black spongy compound infusible at the temperature. It contains a portion of the lead and is probably a compound of the metals with oxygen. The fusible alloy has the appearance of lead, but is brittle, breaks without bending and exhibits a fracture like that of antimony and lead. The specific gravity of the alloy is 10.6, or more if not saturated with lead. By treating it with an excess of nitric acid it is dissolved, and the lead may be thrown down by sulphuric acid, and the arsenic acid or oxide by lime. In thisway I find the alloy is composed of about 9 parts of lead with 2 of arsenic, or 1 atom of each of the metals. The spongy mass treated with nitric acid yields a similar solution, accompanied with a precipitation of oxide of arsenic.
5.Lead and cobalt.The alloy of these two metals is not easily obtained, probably from the great difference of the temperature at which they fuse. Gmelin fused 1 part cobalt with 1, 2, 4, 6 and 8 parts of lead respectively. Alloys were obtained of the specific gravities 8.12, 12.28 (query 8.28?), —, 9.65 and 9.78 respectively. From these specific gravities it is plain the lead had been in great part dissipated by the heat. For the last or greatest specific gravity corresponds nearly to 2 parts lead and 1 of cobalt. (An. de Chimie, 19—357.)
Though it may seem premature to treat of triple compounds in the present chapter, which professedly is limited to compounds of two elements, yet as the triple alloys are few and so immediately connected with the preceding, it will scarcely require an apology for introducing them here.
Soft solders.Solders for plumbers and tin-workers, are required to melt easily, and yet not too low, as they should withstand a heat greater than boiling water. The fusing point of the soft solders is usually between 300-400°. Plumbers’ solder I believe is commonly formed by mixing equal parts of tin and lead. I procured a specimen of 8.9 specific gravity, and its fusing point was 380°. Probably a more perfect compound would be formed by mixing 104 parts tin with 90 lead (2 atoms to 1), which would give a specific gravity of 8.8 and the fusing point 350°.
Tin workers’ solder is made rather more fusible than that of the plumbers. A specimen I got from the workmen was 8.87 specific gravity and fused at 345°. A mixture of 3 parts tin and 2 of lead would have formed an alloy of the same fusibility, but the specific gravity would have been 8.6 or 8.7 only. Probably a rather less proportion of tin with a little bismuth entered into the composition.
Fusible Metal.Tin, bismuth and lead are metals which melt at comparatively low temperatures; and it has been shewn that the alloys of any two of them usually melt at lower temperatures than the mean, oreven than the lower extreme. By analogy it might be inferred that an alloy of tin and lead fused with one of tin and bismuth, would melt below either of the two ingredients. It has been shewn that proportions of bismuth and lead of easiest fusion are 2 atoms bismuth with one of lead; this alloy melts at 250°. An alloy of 2 atoms of bismuth and 1 of tin melts at 260°; and so does that of 1 atom bismuth and 1 tin. These alloys being much more easily fused than any other proportions of these metals, it is from their combinations we are to expect a still further reduction of the fusing point. In fact, a combination of either of the tin and bismuth alloys, with the lead and bismuth alloy, produces almost exactly the same reduction of the fusing temperature.
Thus if 4 atoms of bismuth, 1 of tin and 1 of lead be fused together, the compound melts in boiling water or below 212°. It is equally the case if 3 atoms bismuth, 1 of tin and 1 of lead, are fused together.
The double alloy next to those above mentioned in regard to easy fusion is that of 2 atoms tin, and 1 bismuth. It fuses at 320°. This alloy, united to the one of 2 atoms bismuth and 1 lead, gives a compound of 3atoms bismuth, 2 tin and 1 lead, which fuses very nearly at the same temperature as the above triple alloys.
In reference to weights, the above proportions for the most fusible metals will nearly be,
Most of the elementary books have given the proportions of 8 bismuth, 5 lead and 3 tin; or 5 bismuth 2 lead and 3 tin, which nearly agree with some of the above, and give an alloy fusing below 212°.
Wishing to investigate this subject more fully, and it being obvious from the preceding facts that there are only two proportions of tin and lead to be united with bismuth, to produce the desired effect, namely, either 1 atom of tin with 1 of lead, or 2 atoms of tin with 1 of lead, I proceeded as follows:
1 atom tin (52) + 1 atom lead (90) + 1 atom bismuth (62), were fused together; the fusing point was 270°. The alloy was flexible to a certain degree; and the fracture very small grained. To this alloy 31 grains of bismuth were added successively till it was evident the alloy was growing less fusible; the results were as follows:
From this it appears that 3 parts by weight of tin, 5 of lead, and any proportion of bismuth from 7 to 14 will produce an alloy fusing below 212°; but of these the best is 10 or 11 parts.
Again, 2 atoms of tin were combined with 1 of lead and 3 of bismuth, by gradually adding one half of the tin. The several alloys fused without any material difference at or below 200°. A further addition of tin impaired the property as in the above case with bismuth. I did not think it important to mix 2 atoms of tin and 1 of lead with any other proportion than 3 atoms of bismuth.