Part 13
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 one twelfth 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._
_Alloys of Platina with other Metals._
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 preferred for 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._
_Alloys of Silver with other Metals._
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; the alloy corresponds nearly to 3 atoms silver and 1 arsenic. It is brittle and of a yellowish colour.
_Alloys of Mercury and other Metals: Amalgams._
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 grows hard 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 in mercury, 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 which crystallizes 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.
_Triple, quadruple, &c. Amalgams._
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 of lead 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 along _drags 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 up with 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.
_Alloys of Copper with other Metals._
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 called _bell-metal_; but they receive more particular names according to the purposes for which they are destined, as _bronze_, _speculum metal_, _gun-metal_, &c. those of them which are yellow are frequently confounded in common language with brass, as _brass guns_, &c. Indeed the ancient Greeks and Romans seem to have been in possession of these two alloys, under one and the same name. The =χαλκος= of the Greeks, being used for cutting-instruments, must have signified _bell-metal_, or the alloy of copper and tin as well as brass, as indeed is proved by the analysis of them. The _æs_ of 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 degree of 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 in _bell-metal_ properly 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 any other 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.
[Footnote 20: See a very excellent essay on the alloy of copper and tin by M. Dussaussoy, in the Annales de Chimie & Physique. 5--113.]
(_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 gong analysed 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.