SECTION 17.. Metallic Alloys.

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. These alloys 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.

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 same proportions; 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.

Alloys of Gold with other Metals.

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. 1 to 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 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. 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.

(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.

(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 precision this 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.

(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 form brass, 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 which may 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 the mixture 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; 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 then increasing 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, so that what is 8.2 when cast will be 8.7 when rolled; or it 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 of spelter solder, 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 zinc gradually 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 are ternary combinations 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 be obtained 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 of white copper, and white 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.

Alloys of Iron with other Metals.

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 common tin-plate is 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.

Alloys of Nickel and other Metals.

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.

Alloys of Tin with other Metals.

1. Tin with lead. Tin and lead unite by fusion in any proportion. This alloy, according to Muschenbroek, is harder and much more 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.

Atoms. | Weights | Sp. Gr. by | Sp Gr. by | Fusing | |calculation.| experim. | Point. Tin. Lead. | Tin. Lead. | | | 1 + 1 | .58 + 1 | 9.32 | 9.17 | 430° 2 + 1 | 1.16 + 1 | 8.64 | 8.79 | 350 3 + 1 | 1.73 + 1 | 8.25 | 8.49 | 340 4 + 1 | 2.3 + 1 | 8.00 | 8.10 | 345 5 + 1 | 2.9 + 1 | 7.93 | 8.00 | 350 6 + 1 | 3.47 + 1 | 7.81 | 7.90 | 360

From the above table it appears that when 1 atom of tin is united to 1 of 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 of tutenag. This metal in colour approaches more to silver 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 and brittle 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.

Alloys of Lead with other Metals.

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 and not 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 antimony and 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 this way 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.)

Triple Alloys, Solders; Fusible Metal, &c.

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, or even 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 3 atoms 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,

Bismuth 14 parts -- Lead 5 -- tin 3 ------- 10 ----- -- ---- 5 ------ 3 ------- 5 ----- -- ---- 2½ ------ 3

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:

1 atom tin + 1 lead + 1 bismuth; fuses at 270° 1 -------- + 1 ---- + 1½ ------ -------- 235° 1 -------- + 1 ---- + 2 ------ -------- 205° 1 -------- + 1 ---- + 2½ ------ -------- 200° 1 -------- + 1 ---- + 3 ------ -------- 197° 1 -------- + 1 ---- + 3½ ------ -------- 200° 1 -------- + 1 ---- + 4 ------ -------- 220° 1 -------- + 1 ---- + 4½ ------ -------- 205° semi fluid. 1 -------- + 1 ---- + 5 ------ -------- 240° semi fluid. but it retains a little fluidity down to nearly 200°

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.

APPENDIX.

Since the publication of the second part of the first volume, (1810) some important essays on the subject of heat have appeared, which have a direct bearing upon some points of the doctrine on that subject inculcated in the said volume. It may be proper to state the results, with such remarks and reflections as have occurred in the consideration of them.

In the Annales de Chimie for January 1813, also in the Annals of Philosophy, vol. 2, we find a Memoir on the specific heat of different gases, by M. M. De la Roche and Berard. This exhibits a most laborious and refined series of experiments on this most difficult subject. Great merit seems to be due to them, both for invention and execution.

It is unnecessary to describe the particulars of the apparatus and the mode of conducting the experiments, as a description may be found as above referred. It is sufficient to observe that the calorimeter used was a copper cylinder of 3 inches diameter and 6 in length, filled with water, and having a serpentine tube 5 feet in length, running through the interior and opening at both ends on the outside of the vessels. By means of this tube a regular current of any gas of a given temperature (212°) might be passed through the vessel so as to part with its excess of temperature to the water. The quantity of water and the capacity of the vessel for heat were previously determined; and the quantity of heated gas passed through the calorimeter was determinable at any time, as well as the temperature of the water, from the judicious arrangements.

It is easy to see that when an apparatus of this kind is at work, the gas will impart heat, more or less according to its capacity, to the water; and that the temperature of the calorimeter will gradually ascend till it arrives at a maximum; that is, till the refrigerating effect of the surrounding atmosphere upon the calorimeter is equal to the heating effect of the current of gas.

The following Table exhibits the results of their experiments.

+----------------+---------------------------------------+ | | Specific Heat | | | Of the same bulk.| Of the same weight.| +----------------+------------------+--------------------+ | Air | 1.0000 | 1.0000 | | Hydrogen | 0.9033 | 12.3401 | | Carbonic Acid | 1.2583 | 0.8280 | | Oxygen | 0.9765 | 0.8848 | | Azote | 1.0000 | 1.0318 | | Nitrous Oxide | 1.3503 | 0.8878 | | Olefiant Gas | 1.5530 | 1.5763 | | Carbonic Oxide | 1.0340 | 1.0805 | | Aqueous Vapour | 1.9600 | 3.1360 | +----------------+------------------+--------------------+

They found the specific heats of equal volumes of air of the pressures 29.2 and 41.7 inches of mercury to be nearly as 1 ∶ 1.2396, differing from the ratio of the pressures or densities, which is 1: 1.358.

The above table of the specific heat of the permanent gases (excluding aqueous vapour) was corroborated by the results of another series of experiments in which the principle was varied a little: namely, to find how many cubic inches of each gas at a given temperature were required to raise the temperature of the calorimeter a given number of degrees, and inferring the capacities for heat to be inversely as the quantities of gas employed. The differences in the results were from 1 to 10 per cent., which may be considered small, in experiments of such delicacy.

The ratios of the specific heats of several gases being found, it was highly expedient to find the ratio of the specific heat of water, and that of some one gas, as common air. This was effected by passing a small current of hot water through the calorimeter, and comparing the effect of this current with that of the larger one of air, the requisite care being taken to ascertain the quantity of water passing in a given time and its temperature at the ingress. The result of this experiment was that the specific heat of water is to that of common air as 1 ∶ .25 nearly. By two other experiments, varied from the above, results not much differing were obtained, so that the average of the three gave, water to air, as 1 ∶ .2669.

Reducing the specific heats of the gases to the standard of water as unity, we have the following Table of the specific heats of equal weights of the respective bodies:

Water 1.0000 Air 0.2669 Hydrogen 3.2936 Carbonic Acid 0.2210 Oxygen 0.2361 Azote 0.2754 Nitrous Oxide 0.2369 Olefiant Gas 0.4207 Carbonic Oxide 0.2884 Aqueous Vapour 0.8474

Before we animadvert upon these results, it will be expedient to give an abstract of the not less interesting experiments of Messrs. Dulong and Petit, on heat, as given in the Annales de Chimie and de Physique, vol. 7 and 10.

These gentlemen begin by an investigation of the expansion of air by heat. The absolute expansion of air from freezing of water to boiling had been previously determined by Gay Lussac and myself to be from 8 to 11 nearly: they however extended the enquiry above and below these points of temperature, namely to those of freezing and boiling mercury. From the temperature of freezing mercury or thereabouts, to that of boiling water, they find the expansion of air to keep pace with that of mercury, as indicated by the common thermometer; but from the boiling point of water to that of mercury, the latter expands somewhat more in a proportion gradually increasing: as by the following Table.

TABLE I. +------------------------+-----------------+-----------------------+ | | | Temperature by an | | | | air Thermometer, | |Temperature by Mercurial| Corresponding | corrected for | |Thermometer. |volume of a given| expansion of glass. | | | mass of air. | | |Fahrenheit.| Centigrade.| | Centigrade. | +-----------+------------+-----------------+-----------------------+ | -33° | -36°| 0.8650 | -36.8 | | 32 | 0 | 1.0000 | 0 | | 212 | 100 | 1.3750 | 100 | | 302 | 150 | 1.5576 | 148.70 | | 392 | 200 | 1.7389 | 197.05 | | 482 | 250 | 1.9189 | 245.05 | | 572 | 300 | 2.0976 | 292.70 | | 680 |M. boil 360 | 2.3125 | 350.00 | +-----------+------------+-----------------+-----------------------+

The absolute dilatation of mercury claims their attention. They quote nine authorities for the expansion from freezing to boiling water temperatures; the extremes of these nine are, Casbois ¹/₆₇ of original volume, and mine ¹/₅₀ of the same. They determine it to be ¹/₅₅.₅. By doubling and tripling the elevation of the temperature, they made observations from which are deduced the results of the following Table. The dilatations are for each degree of the thermometer centigrade, to which I have added the corresponding ones for Fahrenheit’s.

TABLE II. +---------------------+-----------------+-------------------------+ | | Mean absolute | Temperatures indicated | |Temperature by an air| dilatations |by dilatation of mercury,| | Thermometer. | of mercury. | supposed uniform. | +---------------------+-----------------+-------------------------+ | Fahr. Cent. | Fahr. Cent. | Fahr. Cent. | | 32° 0° | 0 0 | 32° 0° | | 212 100 | ¹/₉₉₉₀ ¹/₅₅₅₀ | 212 100 | | 392 200 | ¹/₉₉₄₅ ¹/₅₅₂₅ | 400.3 204.61 | | 572 300 | ¹/₉₅₄₀ ¹/₅₃₀₀ | 597.5 314.15 | +---------------------+-----------------+-------------------------+

By a series of observations on the apparent dilatation of mercury in glass vessels, compared with the results in the above tables, they deduce the absolute dilatation of glass for each degree of the thermometer, and the temperature that would be indicated by supposing the uniform expansion of a glass rod adopted as the measure of temperature as under:

TABLE III. +---------------+--------------+-------------------+--------------+ | |Mean apparent | Absolute |Temperature by| |Temperature by |dilatation of | dilatation of |a Thermometer | |an air Thermom.| mercury | glass in |made of glass.| | | in glass. | volume. | | +---------------+--------------+-------------------+--------------+ | Fahr. Cent. | Fahr. Cent.| Fahr. Cent. | Fahr. Cent. | | 212° 100° |¹/₁₁₆₆₄ ¹/₆₄₃₀| ¹/₆₉₆₆₀ ¹/₃₈₇₀₀ | 212 100 | | 392 200 |¹/₁₁₄₃₀ ¹/₆₃₇₈| ¹/₆₅₃₄₀ ¹/₃₆₃₀₀ | 415.8 213.2 | | 572 300 |¹/₁₁₃₇₂ ¹/₆₃₁₈| ¹/₅₉₂₂₀ ¹/₃₂₀₀₀ | 667.2 352.9 | +---------------+--------------+-------------------+--------------+

The absolute dilatations of iron, copper, and platina were investigated with great address, from 0° to 100° and from 0° to 300° centigrade; and were found as per Table below, for each degree of the centigrade thermometer.

TABLE IV. +--------+---------------+--------+---------------+ |Temp. by|Mean dilatation|Temp. by|Mean dilatation| | the air| of iron, |iron rod| of copper | | Therm. | in volume. | Therm. | in volume. | +--------+---------------+--------+---------------| | Cent. | | | | | 100° | ¹/₂₈₂₀₀ | 100° | ¹/₁₉₄₀₀ | | 300 | ¹/₂₂₇₀₀ | 372.6 | ¹/₁₇₇₀₀ | +--------+---------------+--------+---------------+

+-----------+---------------+-----------+ | Temp. by |Mean dilatation| Temp. by | |copper rod | of platina |platina rod| | Therm. | in volume. | Therm. | +-----------+---------------+-----------+ | | | | | 100° | ¹/₃₇₇₀₀ | 100° | | 328.8 | ¹/₃₆₃₀₀ | 311.6 | +-----------+---------------+-----------+

Connected with this subject was another important enquiry, whether the capacities of bodies for heat remain constant at different temperatures, or whether they diminish or increase as the temperature advances. In other words, does a body that requires a certain quantity of heat to raise it from 0° to 100° centigrade, require the same quantity to raise it from 100° to 200°, and from 200 to 300°, &c.; or does it require less or more as we ascend? This enquiry involves that of the measure of temperature. They adopt the uniform expansion of air, or the air thermometer, as the proper measure, and find the capacity of iron,

From 0° to 100° = .1098 0 to 200 = .1150 0 to 300 = .1218 0 to 350 = .1255

the capacity of an equal weight of water being 1.

The following Table exhibits the capacities of seven other bodies according to their results.

TABLE V. +---------+--------------+--------------+ | |Mean capacity |Mean capacity | | | between 0° | between 0° | | | and 100° | and 300° | +---------+--------------+--------------+ |Mercury | .0330 | .0350 | |Zinc | .0927 | .1015 | |Antimony | .0507 | .0549 | |Silver | .0557 | .0611 | |Copper | .0949 | .1013 | |Platina | .0335 | .0355 | |Glass | .1770 | .1900 | +---------+--------------+--------------+

According to this table the capacities of bodies increase with the temperature in a small degree: and the increase, though it would still exist, would be less, if the common mercurial thermometer were the measure of temperature.

Also supposing that thermometers made of these bodies and graduated by immersion in freezing and boiling water into 100°; if these were all immersed in a fluid in which an air thermometer stood at 300°. Then the relative temperatures of the several thermometers would be as under, if measured by the absolute quantity of heat acquired, namely,

Iron 322.2° Silver 329.3 Zinc 328.5 Antimony 324.8 Glass 322.1 Copper 320.0 Mercury 318.2 Platina 317.9

From these observations they infer that the law which has been promulgated for the refrigeration of bodies, cannot be strictly true: namely, that bodies part with heat in proportion as their temperature exceeds that of the surrounding medium.

Some animadversions on the general laws relative to the phenomena of heat, announced in my elements of Chemical Philosophy (page 13) then follow, together with a table drawn up to show the discordance between the air thermometer and the mercurial thermometer, both being graduated in the manner I proposed in the said elements. On these points I may have to remark in the sequel.

The first part of the Essay concludes with some remarks to shew why a preference should be given to the air thermometer, or more strictly, the thermometer whether of mercury or any other body, supposed to be graduated so as to correspond with an air thermometer of equal degrees.

The Second Part of the Essay is on

The Laws of Refrigeration.

Adopting the air thermometer as the most eligible measure of temperature, Messrs. Dulong and Petit proceed to investigate the laws of the refrigeration of bodies, under a great variety of circumstances, in vacuo and in air or gases of different kinds and densities. The inquiry abounds with experiments and observations evincing great skill and acuteness; but which it will not suit our purpose to detail. It may suffice for us to give a general summary of the Laws deduced by them from their experiments, at the same time recommending all those who feel sufficient interest in the subject to peruse the essay at large, which exhibits a profound philosophical train of experiments, the results of which are illustrated by the aid of mathematical generalization.

“Law 1. If one could observe the cooling of a body placed in a vacuum, and surrounded by a vessel absolutely destitute of heat, or otherwise deprived of the power of radiating heat, the velocities of cooling would decrease in geometrical progression when the temperatures diminished in arithmetical progression.”

“Law 2. The temperature of a vessel containing a vacuum being constant, and a body being placed in it to cool, the velocities of cooling for excesses of temperature in arithmetical progression, decrease as the terms of a geometrical progression diminished by a constant number. The ratio of this progression is the same for the cooling of all kinds of bodies, and is equal to 1.0077.”

“Law 3. The velocity of cooling in a vacuum for the same excess of temperature, increases in geometrical progression, the temperature of the vessel circumscribing the vacuum increasing in an arithmetical progression. The ratio of the progression is the same as above, namely 1.0077 for all kinds of bodies.”

“Law 4. The velocity of cooling due to the sole contact of a gas is entirely independent of the nature of the surface of the cooling bodies.”

“Law 5. The velocity of cooling due to the sole contact of a gaseous fluid varies in a geometrical progression, while the excess of temperature itself varies in a geometrical progression. If the ratio of this second progression be 2, that of the first is 2.35, whatever be the nature of the gas and its elastic force.”

“This Law may be likewise announced by saying that the quantity of heat carried off by a gas is in all cases proportional to the excess of the temperature of the heated body raised to the power whose index is 1.233.”

“Law 6. The cooling power of a gaseous fluid diminishes in a geometrical progression, when its tension itself diminishes in a geometrical progression. If the ratio of this second progression is 2, the rate of the first is 1.366 for atmospheric air; 1.301 for hydrogen; 1.431 for carbonic acid; and 1.415 for olefiant gas.”

“This law may also be presented as follows: The cooling power of a gas, all other things being alike, is proportional to a certain power of the pressure. The exponent of this power depends on the nature of the gas, and is for air 0.45; for hydrogen 0.315; for carbonic acid 0.517; and for olefiant gas 0.501.”

“Law 7. The cooling power of a gas varies with its temperature in such a manner that if the gas can dilate so as to preserve the same uniform tension, the cooling power will be as much diminished by the rarefaction of the gas, as it is increased by its augmentation of temperature; so that definitively it depends only on its tension.”

* * * * *

Another ingenious Essay was published by Messrs. Dulong and Petit, in the Annal. de chimie et de physique, vol. 10, namely, “Researches on some important points of the theory of heat.”--One object is to ascertain the specific heats of bodies with superior precision. A table of the specific heats of certain metals, found by their method, is given, together with the weights of the atoms of those metals, and the products of the specific heats and weights of the atoms, as under:

+----------+---------------+--------------+--------------+ | | | |Product of the| | | | |weight of each| | |Specific heats,|Weights of the| atom by the | | | that of water |atoms, that of|corresponding | | | being 1 |oxygen being 1| capacity. | +----------+---------------+--------------+--------------+ |Bismuth | 0.0288 | 13.300 | 0.3830 | |Lead | 0.0293 | 12.950 | 0.3794 | |Gold | 0.0298 | 12.430 | 0.3704 | |Platinum | 0.0314 | 11.160 | 0.3740 | |Tin | 0.0514 | 7.350 | 0.3779 | |Silver | 0.0557 | 6.750 | 0.3759 | |Zinc | 0.0927 | 4.030 | 0.3736 | |Tellurium | 0.0912 | 4.030 | 0.3675 | |Copper | 0.0949 | 3.957 | 0.3755 | |Nickel | 0.1035 | 3.690 | 0.3819 | |Iron | 0.1100 | 3.392 | 0.3731 | |Cobalt | 0.1498 | 2.460 | 0.3685 | |Sulphur | 0.1880 | 2.011 | 0.3780 | +----------+---------------+--------------+--------------+

The inference intended from this Table is pretty obvious, namely, that the atoms or ultimate particles of the above bodies contain or attach to themselves the same quantity of heat, or have the same capacity. This principle the authors think will apply to the simple atoms of all bodies, whether solid, liquid, or elastic; but they hold it does not apply to compound atoms. It differs therefore essentially from a suggestion of mine, made eighteen years ago, (see Vol. I. page 70,) that the quantity of heat belonging to the ultimate particles of all elastic fluids, must be the same under the same pressure and temperature. They seem to apprehend, from experience, that a very simple ratio exists between the capacities of compound atoms and that of the elementary atoms. They draw another inference from their researches, that the heat developed at the instant of the combination of bodies, has no relation to the capacity of the elements; this loss of heat, they argue, is often not followed by any diminution in the capacity of the compounds. They seem to think that electricity developes heat in the act of combination; but they do not deny that a change of capacity may sometimes ensue, and heat be developed from this cause.

Remarks on the above Essays.

Results nearly agreeing with those of De la Roche and Berard, on the capacity of certain elastic fluids for heat, were about the same time obtained by M. M. Clement and Desormes. (See Journal de Physique, Vol. 89--1819.) Such results, impugning some of the most plausible doctrines of heat, could not be admitted but upon very good authority. I remained doubtful, in some degree, till satisfied by my own experience. I procured a calorimeter of the construction of De la Roche’s, and to simplify the experiment, instead of forcing a given volume of hot air through the calorimeter to impart heat to the water, I drew, by means of an air-pump, a certain volume of atmospheric (or other air) of the common temperature, through the calorimeter filled with hot water, in order to find how much this process would accelerate the cooling. From several experiments of this kind, I am convinced that the capacity of common air for heat is very nearly such as the above ingenious French chemists have determined. That is, it is about ¹/₇ part only of what Dr. Crawford deduced from his experiments, and nearly the same part of what I inferred from my theoretic view of the specific heats of elastic fluids. (See Vol. I. pages 62 and 74.)

Indeed M. M. De la Roche and Berard appear to have been puzzled with the admission of their own results. The combined heats of oxygen and hydrogen gases give only .6335 for the specific heat of water; whereas by experiment the heat of water is found to be 1, notwithstanding an immensity of heat is evolved during the combination of these gases.

“It is necessary therefore,” they observe, “to abandon the hypothesis which ascribes the evolution of heat in cases of combination to a diminution of specific heat in the bodies combined, and admit with Black, Lavoisier, and Laplace, and many other philosophers, the existence of caloric in a state of combination in bodies.” I am not aware of any writer that denies the existence of caloric in a state of combination of bodies. Dr. Crawford, who would be thought the most likely to err in this respect, maintains, “that elementary fire is retained in bodies partly by its attraction to those bodies and partly by the action of the surrounding heat,” and that “its union with bodies will resemble that particular species of chemical union wherein the elements are combined by the joint forces of pressure and of attraction.” (On animal heat, 2d edition, page 436.) He is perhaps somewhat unfortunate in his instance in the combination of carbonic acid and water; muriatic acid or ammonia and water would have been more in point.

The truth is, these important experiments shew that in elastic fluids the increments of temperature are not proportional to the whole heat, compared with the like increments of temperature and whole heat in those bodies when in the liquid and solid states.

The specific heats of bodies, it is well known, are determined by means of the relative quantities of heat necessary to raise the temperature of those bodies a certain number of degrees. They are expressed by the ratios of those quantities. If the capacities of the same bodies for heat were permanent at all temperatures, then these ratios would also express those of the whole quantities of heat in bodies. In fact, most authors represent the specific heats as expressing both the ratio of the total quantities of heat in bodies, and of the relative quantities to raise their temperature a given number of degrees; but it is the latter only which they accurately represent, and the former only hypothetically.

In regard to bodies in the solid and liquid forms, all experience shews that their capacities for heat are nearly if not accurately constant within the common range of temperature; it seems therefore not unreasonable to infer that the whole quantity of heat in each is proportional to their increments. When, however, a solid body by an increase of temperature assumes a fluid form, and absorbs heat without any increase of its temperature, its total quantity of heat is thus increased; and it is contended by the writers on capacity, that the increments of heat afterwards are increased in the same proportion as the total quantities. This is probable enough; but it ought to be proved in several instances by direct experiment before it can safely be admitted as a general principle; more especially now since the analogy in the case of a liquid becoming an elastic fluid is found to fail in this particular. As an instance of uncertainty, the capacity of ice to water has been found as 9 to 10 by one person, and as 7.2 to 10 by others; such wide difference in the results shows there must be a difficulty in determining the specific heat of ice, and that it may even be doubted whether the specific heat of ice or water is greatest.

From the foregoing detail of experiments on elastic fluids, it appears evident that such fluids exhibit matter under a form in which it has the greatest possible capacity for heat, when capacity is understood to denote the total quantity of heat connected with the fluid; but if the capacity or specific heat is meant to denote the quantity of heat necessary to raise the body a given number of degrees of temperature, then the elastic fluid form of matter is that which has the least capacity for heat of any known form of the same matter. When therefore we use the terms specific heat as applied to elastic fluids we should henceforward carefully distinguish in what sense they are used; but the terms may still be indifferently used in the one or the other sense as applied to liquids and solids, till some more decisive experiments shew that a distinction is required. Probably the anomalies that have occurred in investigations of the zero of cold, or point of total privation of heat, are in part due to the want of accordance between the ratio of the total quantities of heat in bodies, and the ratio of the quantities producing equal increments of temperature.

The greatest possible quantity of heat which a given weight of elastic fluid can contain is when the dilatation of the fluid is extreme. For, condensation, whether arising from mechanical pressure or from increased attraction of the atoms of matter for each other, tends to dissipate the heat, by increasing its elasticity. Hence increase of temperature, at the same time that on one account it increases the absolute quantity of heat in an elastic fluid, diminishes the quantity on another account by an increase of pressure, if the fluid be not suffered to dilate. This is well known from the fact that condensation produces increase of temperature in elastic fluids.

When it is considered that all elastic fluids expand the same quantity by the same increase of temperature, it might be imagined that all of them would have the same capacity, or require the same quantity of heat to produce that expansion. The results of De la Roche and Berard do not seem to admit of this supposition, though the differences of the capacities of elastic fluids of equal volumes are not very great. There is a remarkable difference too between their results and those of Clement and Desormes, in regard to hydrogen gas: namely, .9033 and .6640; also in carbonic acid gas, 1.2583 and 1.5. The subject deserves further investigation.

In reference to the experiments of Dulong and Petit, on the relative expansions of air and mercury by heat, I have no doubt their results are good approximations to the truth. My former experiments were chiefly made in temperatures between 32° and 212°, and I found, as General Roi had done, the expansion of air to be somewhat greater in the lower half than in the upper half of that interval, compared with mercury. On a repetition of the experiments, I think the difference is less than I concluded it to be, and I find that the like coincidence of the air scale and mercurial, continues down to near freezing mercury; at least the difference will not be so great as my new table of temperature makes it at page 14. I have made some experiments on the expansions of air above 212°, which lead me to adopt the results of Dulong. On a comparison of the air and mercurial thermometer upon the laws which I pointed out, namely, the former expanding in geometrical progression to equal intervals of temperature, and the latter expanding as the square of the temperature reckoned from its freezing point, it appears that in the long range of 600° from freezing water to boiling mercury, the greatest deviation of the two thermometers does not exceed 22°. However, the great deviation of the scales between the temperatures of freezing water and freezing mercury, is sufficient to shew, as Dulong and Petit have observed, that their coincidence is only partial. Like the scales of air and mercury, which are so nearly coincident from -40° to 212° that scarcely any difference is sensible, though no one doubts of its existence; yet afterwards the differences become obvious enough, and the greater the farther we advance.

Expansion of Mercury. See page 34, vol. I. I have overrated the expansion of glass bulbs (as will be seen presently,) and hence that of mercury; my expansion of mercury corrected on account of the glass, will be ¹/₅₃ nearly, which leaves it still greater than Dulong’s. The 2nd table of Dulong is valuable, on account of its affording us information of the rate of expansion in the higher degrees of temperature, from a given or standard air thermometer.

Iron, Copper, and Platina.

Expansion of Glass.--By the 3rd Table of Dulong and Petit, it appears these ingenious chemists found the expansion of glass for 180°, or from 32° to 212°, very nearly the same as had been determined previously by Smeaton and others. It also expands increasingly with the temperature, whether it is estimated by the air or mercurial standard. This was observed by Deluc, but more extensively by the present authors. The expansions of iron, copper, and platina, from 32° to 212° as detailed in the 4th table, agree nearly with the results of others; but the expansions in the higher part of the scale manifest some remarkable facts not before known. Platina not only expands the least of the above bodies, but its expansion is almost equable; iron expands more than glass and less than copper, but the most unequally of any one, the expansion increasing rapidly as the temperature advances. These facts explain some others which have fallen under my observation. I was formerly surprised to find glass and iron expand so nearly alike (see vol. I. page 31); but it now appears that iron increases more slowly in proportion than glass about the freezing point. More recently I procured a small thermometrical vessel of platina to contain water like those described at page 31, vol. I, and having filled it and treated it as the other metallic vessels, I was again surprised to find that the apparent greatest density of water in this vessel was at 43°, whereas I expected to have found it below 42°, the point for glass vessels. This observation, in conjunction with Dulong’s, shews, that platina expands more than iron at low temperatures, though for a range of 300° the whole expansion of the platina is to that of the iron as 2 to 3 nearly. Hence the error (for I now consider it as such) which I was led into with respect to the expansion of glass bulbs, (see vol. I. page 32) and subsequently into that of the expansion of mercury abovementioned. It is not the expansion of glass which approaches that of iron, but it is the reverse, which occasions the two bodies to meet so nearly in the table, page 31. This consideration will affect the point of greatest density of water also; for, the less the expansion of iron and glass, the nearer will be the points of real and apparent greatest density of water, contained in vessels of those materials. My observations on brown earthenware are scarcely to be relied upon from the difficulty of making such vessels water tight: but the common white ware I have verified repeatedly since the publication of that table, and am satisfied the point of apparent greatest density, is at or near 40° in such vessels; hence the real maximum density of water must be below 40°. I am inclined to adopt 38° as the most proximate degree.

Capacities of bodies for heat. In the 5th table of Dulong, we have the specific heats of glass and of six metals, determined between freezing and boiling water: that of iron is given before. So far the question does not involve that of the measure of temperature. Their results afford no striking differences from those previously determined; however, it is desirable to find a greater accordance amongst philosophers in this respect. The experiments which give the specific heats between 0° and 300° centigrade, are original and interesting. The results go to shew that the capacities of bodies increase in a small degree with the temperature. But supposing that these results may be relied upon as accurate (which can scarcely be affirmed of any former ones) still the character of them may be changed by adopting a different measure of temperature.

The Essay of M. M. Dulong and Petit, in the 10th vol. of the An. de chimie (see An. of Philosophy, vol. 14th, 1819) manifests great ingenuity. It does not appear, however, so fortunate either in theory or experiment as the former one. It would be difficult to convince any one, either by reasoning or by experience that a number of particles of mercury at the temperature of -40°, whether in the solid,, liquid, or elastic state, have all the same capacity for heat. Indeed the experiments of De la Roche and Berard, if they are to be credited, demonstrate the inferior capacity of condensed air to rarefied air; and if the same body changes its capacity in the elastic form, it may well be concluded that all the three forms have not the same capacity. M. M. Dulong and Petit have themselves shewn, in their former essay, (see page 276) that solid bodies vary in their capacities for heat, and that scarcely any two bodies, vary alike; hence it is impossible that the product of the weight of the atom and specific heat of the body should be a constant quantity. Their specific heat of certain metals differ greatly from what is found by others. For instance, they make the specific heat of lead .0293; the lowest authority I have seen is Crawford, .0352, and the highest Kirwan .050; from repeated trials I have lately found it, upon an average, .032. The weights of some of the atoms in their table, differ materially from what are commonly received; for instance, bismuth is 13.3 instead of 9; also copper, silver, and cobalt, are only half the weights of some authors. The gases too are unfortunate examples. Oxygen gas gives a product of .236 instead of .375; azotic gas gives a product .1967, if oxygen be to azote as 7 to 5, but a product of .393 if oxygen be to azote as 7 to 10: by Dr. Thomson’s ratio of oxygen to azote, 4 to 7, the product will be .482, very different from .375. Hydrogen will give a product of .47 or .41 instead of .375. All these differences, it may be said, are occasioned by errors in the specific heats of the gases; but if errors of this magnitude can still subsist after all the care that has been taken, we shall scarcely know what to trust in experimental philosophy.

If M. Dulong would assume all his simple elements in an elastic state and under one uniform pressure, the hypothesis would then make a part of mine (vol. 1. page 70), and there is great reason to believe it would be either accurately true or a good approximation; but to suppose that some of the bodies should be in a solid state, having their particles united by various degrees of attraction, others fluid, and others in the elastic state, without any material modifications of their heat arising from these circumstances, appears to me to be in opposition to some of the best established phenomena in the mechanical philosophy.

Their observations on the specific heat of compound elements, on the relation of the heat developed by combination, as compared with the heat of the elements before and after the combination, &c., are not supported by a detail of actual experience. Heat given out by chemical changes they suppose not to have been previously in a state of combination with the elements. As an argument, the heat given out by charcoal kept in a state of ignition, by a current of galvanic fluid, is adduced. It is true this case is most easily explained, by allowing that the galvanic fluid is in such circumstances converted into heat. But the charcoal does not undergo any chemical change, and therefore this is not a case in point.

All modern experience concurs in shewing that the heat of combustion is primarily dependent on the quantity of oxygen combining. The heat evolved by the combustion of phosphorus and hydrogen is very nearly, if not accurately, in proportion to the oxygen spent. The heat by the combustion of charcoal is not in a much less ratio: and I find the heat in burning carbonic oxide, carburetted hydrogen and olefiant gas is the same as in burning hydrogen gas, provided the combining oxygen is the same.

One difficulty seems to have occurred to M. M. Dulong and Petit. They all along conceive that the specific heats of bodies, that is, the heats producing equal increments of temperature, must necessarily be proportionate to their whole heat. This is purely hypothetical, till established by experiment. The generality of writers on specific heat had conceived it almost confirmed by experiment. The results of Delaroche and Berard have shewn that in elastic fluids the increments of heat are not proportional to the whole quantities, but on the contrary are less when a body is elastic than when liquid. Indeed some writers have argued this should be the case; because a body nearly saturated with another has less affinity for it left. It is plain then that oxygen gas or any other elastic fluid, may have a small specific heat in the sense above defined, and yet have an almost unlimited quantity of heat. I am not aware of any one established fact that does not admit of an explanation upon the hypothesis that heat exists in definite quantities in all bodies, and is incapable of any change, except perhaps into one of the other equally imponderable bodies, light or electricity.

NEW TABLE OF THE Forces of Vapours in Contact with the Generating Liquids at Different Temperatures.

(A) = Temperatures by the common thermometer. (B) = Ether vapour, ratio 2 Spec. Gravity .72 (C) = Sulphuret of carbon vapour, ratio 1.978 (D) = Alcohol vapour, ratio 2.7 Spec. Gravity .82 (E) = Acetic acid vapour, ratio 2.57 (F) = Water, ratio 2.602() -----+--------+--------+--------+--------+------- (A) | (B) | (C) | (D) | (E) | (F) -----+--------+--------+--------+--------+------- | Inches | Inches | Inches | Inches |Inches | of M. | of M. | of M. | of M. | of M. -----+--------+--------+--------+--------+------- 7° | 3.75 | 3.134 | .193 | | .11 35 | 7.5 | 6.20 | .560 | .27 | .29 65+ | 15. | 12.26 | 1.51 | .69 | .75 97 | 30 | 24.26 | 4.07 | 1.77 | 1.95 133 | 60 | 48. | 11.00 | 4.54 | 5.07 173 | 120 | | 29.70 | 11.7 | 13.18 220 | 240 | | 80.2 | 30. | 34.2 272 | | | | | 88.9 340 | | | | | 231 -----+--------+--------+--------+--------+-------

This is an improved and extended table of the force of vapour, similar to that at page 14, vol. I. It shews that the different vapours increase inforce in geometrical progression, to certain intervals of temperature, the same to most or all liquids. These intervals of temperature were presumed in the former table, to be in reality equal to one another; but the accuracy of this last notion has been questioned.

TABLE, Shewing the expansion of air, and the elastic force of aqueous and ethereal vapour, at different temperatures. ----------+---------+---------------+----------------+------------- | | Utmost force of | Temperat. | Vol. +---------------+----------------+Weight of 100 | of air. |Aqueous vapour.|Ethereal vapour.| cubic inches ----------+---------+---------------+----------------+ of aqueous -28° | 420 | | | vapour. -20 | 428 |Inches of Merc.|Inches of Merc. | -10 | 438 +---------------+----------------+------------- 0 | 448 | .08 | | Grains. 10 | 458 | .12 | | 20 | 468 | .17 | | 30 | 478 | .24 | | ----------+---------+---------------+ | 32° | 480 | .26 | 7.00 | .178 33 | 481 | .27 | 7.18 | .184 34 | 482 | .28 | 7.36 | .191 35 | 483 | .29 | 7.54 | .197 36 | 484 | .30 | 7.73 | .203 37 | 485 | .31 | 7.92 | .209 38 | 486 | .32 | 8.11 | .216 39 | 487 | .33 | 8.30 | .222 40 | 488 | .34 | 8.50 | .229 41 | 489 | .35 | 8.70 | .235 42 | 490 | .37 | 8.90 | .245 43 | 491 | .38 | 9.10 | .255 44 | 492 | .40 | 9.31 | .267 45 | 493 | .41 | 9.52 | .275 46 | 494 | .43 | 9.74 | .284 47 | 495 | .44 | 9.96 | .293 48 | 496 | .46 | 10.18 | .303 49 | 497 | .47 | 10.41 | .313 50 | 498 | .49 | 10.64 | .323 51 | 499 | .50 | 10.87 | .329 52 | 500 | .52 | 11.10 | .341 53 | 501 | .54 | 11.34 | .354 54 | 502 | .56 | 11.59 | .366 55 | 503 | .58 | 11.85 | .378 56 | 504 | .59 | 12.12 | .384 57 | 505 | .61 | 12.39 | .396 58 | 506 | .62 | 12.66 | .402 59 | 507 | .64 | 12.94 | .414 60 | 508 | .65 | 13.22 | .420 61 | 509 | .67 | 13.51 | .432 62 | 510 | .69 | 13.80 | .444 63 | 511 | .71 | 14.10 | .456 64 | 512 | .73 | 14.41 | .468 65 | 513 | .75 | 14.72 | .480 66 | 514 | .77 | 15.04 | .492 67 | 515 | .80 | 15.36 | .509 68 | 516 | .82 | 15.68 | .521 69 | 517 | .85 | 15.90 | .539 70 | 518 | .87 | 16.23 | .551 71 | 519 | .90 | 16.56 | .569 72 | 520 | .92 | 17.00 | .580 73 | 521 | .95 | 17.35 | .598 74 | 522 | .97 | 17.71 | .610 75 | 523 | 1.00 | 18.08 | .627 76 | 524 | 1.03 | 18.45 | .645 77 | 525 | 1.06 | 18.83 | .662 78 | 526 | 1.09 | 19.21 | .680 79 | 527 | 1.12 | 19.60 | .700 80 | 528 | 1.16 | 20.00 | .721 ----------+---------+---------------+----------------+-------------

Applications of the above Table.

These tables will be found of great use in reducing volumes of air from one temperature or pressure to any other given one: also in determining the specific gravities of dry gases from experiments on those saturated with or containing given quantities of aqueous or other vapours.

As several writers, and some of considerable eminence, have given erroneous or imperfect formulæ on these subjects, more particularly with regard to the effect of aqueous vapour in modifying the weights and volumes of gases, it has been thought proper to subjoin the following precepts and examples for the use of those who are not sufficiently conversant in such calculations.

The 5th column of the above table, or weight of aqueous vapour, is new, and may therefore require explanation. Gay Lussac is considered the best authority in regard to the specific gravity of steam; but it would be well if his results were confirmed or corrected, as they are of importance. According to his experience, the specific gravities of common air and of pure aqueous vapour, of the same temperature and pressure, are as 8 to 5, or as 1 to .625. Now I assume that 100 cubic inches of common air, free from moisture, of the temperature 60° and the pressure of 30 inches of mercury, weigh 31 grains nearly. It is an extraordinary fact that philosophers are not agreed upon the absolute weight of a given volume of common air. Most authors now assume the weight of 100 inches = 30.5 grains, whilst according to my experience it is more than 31 grains. If common air be assumed 31 grains, steam would be 19⅜ grains for 100 cubic inches, at the same temperature and pressure, could it subsist; but as it cannot sustain that pressure at the temperature of 60° we must deduct according to the diminished pressure, the utmost force of steam at 60° being .65 parts of an inch of mercury, we have 30 inches ∶ 19⅜ grains ∷ .65 ∶ .420 grains = the weight of 100 cubic inches of aqueous vapour at 60° and pressure .65 parts of an inch; which is the number given above in the table. The like calculation is required for any other pressure: but in addition to this, there is to be an allowance for the temperature from the 2d column: Thus, let the weight of 100 cubic inches of steam at 32° be required. We have 30 inch. ∶ 19⅜ grs. ∷ .26 inch. ∶ .1679 grs.; the weight of 100 inches of steam at 60°; then if 480 ∶ 508 ∷ .1679 ∶ .178 grs. = weight of 100 cubic inches of steam at 32° and pressure .26 parts of an inch, the tabular number required.

Examples.

1. How many cubic inches of air at 60° are equivalent in weight to 100 cubic inches at 45°?

By the column headed volume of air we have this proportion, if 493 ∶ 508 ∷ 100 inch. ∶ 103.04 inches, the volume required.

2. How many cubic inches of air with the barometer at 30 inches height, are equal in weight to 100 cubic inches when the barometer stands at 28.9 inches?

Rule. The volume of air being inversely as the pressure, we have, 30 ∶ 28.9 ∷ 100 inches ∶ 96⅓ inches the answer.

3. How many cubic inches of dry air are there in 100 inches saturated with aqueous vapour, at the temperature of 50°, and pressure 30 inches of mercury?

Here the formula

(p - f) ----------- p

applies, where p denotes the atmospheric pressure at the time, and f denotes the utmost force of vapour in contact with water at the temperature. Hence p = 30, f = .49 per table, and we have

(p - f) (30 - .49) 29.51 ----------- = ----------- = ----- = 98¹¹/₃₀, or p 30 30

98¹¹/₃₀ percent dry air. & 1¹⁹/₃₀ vapour. --------- 100.

If the vapour of ether is assumed, then f = 10.64, and we have

(p - f) (30 - 10.64) 19.36 ----------- = ----------- = ----- = p 30 30

.645, ... or 64½ per cent dry air. 35½ per cent ethereal vapour. ----- 100

4. Suppose we find by trial the weight of 100 cubic inches of common air saturated with vapour at 60°, the barometer standing at 30 inches to be 30.5 grains, and the weight of hydrogen gas in like circumstances to be 2.118 grains; query the weights of 100 cubic inches of each gas free from vapour, and their specific gravities, the temperature and pressure being as above?

If 30.5 ∶ 2.118 ∷ 1 ∶ .0694 = sp. gr. of vapourized hydrogen, that of vapourized air being 1. Subtracting .42 grs. (weight of vapour per table) from 30.5 grs., leaves 30.08 grains; and subtracting .65 parts of an inch from 30 inches, leaves 29.35 inches. Hence 100 cubic inches of dry air at the pressure of 29.35 inches, weigh 30.08 grains; and we have 29.35 ∶ 30 ∷ 30.08 ∶ 30.746 grains, the weight of 100 inches of dry air. Again, subtracting .42 grs. from 2.118, leaves 1.698 grains = weight of 100 cubic inches of hydrogen of 60° and sustaining the pressure of 29.35 inches; whence if 29.35 ∶ 30 ∷ 1.698 ∶ 1.736 grains, weight of 100 inches of dry hydrogen; and 30.746 ∶ 1.736 ∷ 1 ∶ .05645 = sp. gr. of dry hydrogen, that of dry air being unity. Or the results may be exhibited as under:

Weight of 100 cubic inches. Sp. Gravities.

Vap. air 30.5 grains 1 14.4 Vap. hydrogen 2.118 ---- .0694 1

Dry air 30.746 grains 1 17.7 Dry hydrogen 1.736 ---- .05645 1

FORMULÆ FOR DETERMINING THE PROPORTIONS OF COMBUSTIBLE GASES IN MIXTURES.

It frequently happens, especially in the decomposition of vegetable substances by heat, that the product consists of several combustible gases in mixture, and it is desirable to determine the proportions of each of those which collectively constitute the mixture. The following forms will be found useful for this purpose.

1. Carbonic oxide and hydrogen.

Let x = the volume of carbonic oxide, y = that of hydrogen, w = that of mixture, and a = that of carbonic acid, produced by exploding the mixed gases with oxygen over mercury.

Then the carbonic oxide, or x = a, and the hydrogen, or y = w - a.

2. Sulphuretted hydrogen and hydrogen.

Let x = the volume of sulphuretted hydrogen, y = that of hydrogen, w = that of the mixture, and g = the oxygen spent in the combustion of w.

Then because x + y = w, and 1½x + ½y = g; we have x = g - ½w, and y = 1½w - g.

3. Phosphuretted hydrogen and hydrogen; also carburetted hydrogen and hydrogen, and carburetted hydrogen and carbonic oxide.

The notation being as above, we have x + y = w, and 2x + ½y = g (see page 171): and,

2g - w 4w - 2g x = -----------, and y = -----------. 3 3

4. Olefiant gas and carburetted hydrogen.

The notation being as above, we have

x + y = w, and 3x + 2y = g; whence x = g - 2w and y = 3w - g.

5. Carburetted hydrogen, carbonic oxide and hydrogen.

Let x = carburetted hydrogen, y = carbonic oxide, z = the hydrogen, g = the oxygen spent in the combustion of w volumes of mixed gas, and a = the carbonic acid produced.

Then x + y + z = w, x + ½y + ½z = g, and 2x + y = a.

whence we have

2g - w 3a - 2g + w x = -----------, y = ----------------- 3 3

and z = w - a.

6. Olefiant gas, carburetted hydrogen and carbonic oxide.

Let a = the olefiant gas, y = the carburetted hydrogen, and z = equal the carbonic oxide, g = the oxygen entering into combination, and a = the carbonic acid produced; also w = the whole volume as before.

Then we have x + y + z = w, 3x + 2y + ½z = g, and 2x + y + z = a.

Whence x = a - w,

y = 4w - 5a + 2g -------------------, 3

and z = ⅔(w + a - g).

7. Superolefiant gas, carburetted hydrogen, and carbonic oxide.

Let x = volume of superolefiant, y = volume of carburetted hydrogen, z = volume of carbonic oxide, g = the oxygen combining, a = carbonic acid produced, and w = volume of mixed gas.

Then x + y + z = w, 4½x + 2y + ½z = g, and 3x + y + z = a.

Whence x = a - w ----------, 2

y = 3w - 4a + 2g ------------------, 3

and z = 3w - 4g + 5a -------------------. 6

8. Superolefiant gas, carburetted hydrogen, carbonic oxide, and hydrogen.

This is the mixture of gases obtained by a red heat from coal and oil, after being freed from carbonic acid, &c., by the usual means.

This mixture requires a very complicated formula, in consequence of the specific gravities of the gases entering into the calculus. The importance of the subject however may be an apology for the labour.

Let x = vol. of superolefiant, S its sp. gr. y = vol. of carb. hydrogen, ∫ its sp. gr. z = vol. of carbonic oxide, c its sp. gr. & u = vol. of hydrogen, s its sp. gr.

C = specific gravity of the mixture, g = oxygen, a = carbonic acid, and w = whole volume of mixture as before.

Then we have x + y + z + u = w 4½x + 2y + ½z + ½u = g 3x + y + z = a and Sx + ∫y + cz + su = Cw.

Whence u =

(3S + 5c - 8∫)a - (4c - 4∫)g - (3S + 6C - 6∫ - 3c)w -------------------------------------------------------------------- 8∫ + c - 3S - 6s.

The value of the hydrogen being obtained, it may be subtracted from w, and the remainder will be best divided into three portions, by the preceding formula.

HEAT PRODUCED BY THE COMBUSTION OF GASES.

Subsequent experience to that detailed at page 77, Vol. 1. has furnished the following more correct results of the heat produced by the combustion of pure gases.

Hydrogen, combustion of it raises an equal volume of water 5° Carbonic Oxide 4½ Carburetted Hydrogen, or Pond Gas 18 Olefiant Gas 27 Coal Gas (varies with the gas from 10° to) 16 Oil Gas (varies also with the gas from 12° to) 20

Generally the combustible gases give out heat nearly in proportion to the oxygen they consume. See note at the end of Vol. 4, new series of the Manchester memoirs.

ABSORPTION OF GASES BY WATER, &c.

This curious subject has attracted much less attention than it deserves. Very little has been published relating to it since the time of Dr. Henry’s essays and my own, now more than twenty years ago. The only author I remember is M. Saussure of Geneva, who published a similar essay about twelve years afterwards. See Thomson’s Annals of Philosophy, Vol. 6. He investigates the quantities of gases absorbed by various solid bodies, in a manner which I do not fully comprehend; he then treats of the absorption of gases by liquids, adverting at the same time to Dr. Henry’s experiments and mine. My enquiries were principally confined to one liquid, water; but I made a few trials with others, such as weak aqueous solutions of salts, alcohol, &c., and observing no remarkable differences, I concluded somewhat too hastily that “most liquids free from viscidity, such as acids, alcohol, &c., absorb the same quantity of gases as pure water.” Manchester memoirs, new series, Vol. 1. M. Saussure however asserts that there are considerable differences in liquids in this respect. He finds sulphuretted hydrogen to be more absorbable by water than Dr. Henry and I did; in this I find he is right. Water takes about 2½ its bulk of this gas when pure; and it seldom had been obtained unmixed with hydrogen when Dr. Henry and I made our experiments upon its absorption. In regard to carbonic acid, nitrous oxide, and olefiant gas, M. Saussure nearly agrees with us; but his results with oxygen gas, carbonic oxide, carburetted hydrogen, hydrogen and azote, would prove that water absorbs twice the quantities of each that we have assigned. I have no doubt he is wrong in the less absorbable gases. In the case of absorption of mixed gases, Saussure has given four examples, in which he finds the results to militate against my theoretic view, as stated at page 201, Vol. 1.; namely, that water takes the same quantity of each in a mixed state as it would do if they were separate, and in other respects in like circumstances. But I have shewn in the Annals of Philos. Vol. 7, 1816, that his results coincide as near as any one can expect with the views which I have all along taken of this subject.

It will be seen, page 173, that another gas has been found to coincide with olefiant gas in absorbability; namely, phosphuretted hydrogen.

FLUORIC ACID.--DEUTOXIDE OF HYDROGEN.

In treating of Fluoric acid, (Vol. 1, page 277) we came to the conclusion that this acid was probably constituted of two atoms of oxygen, and one of hydrogen, and have figured it accordingly (Plate 5, fig. 38). Subsequent experience however has shewn that deutoxide of hydrogen, though it can be formed synthetically, is not the same thing as fluoric acid. We are indebted to M. Thenard for the discovery of this curious compound, the deutoxide of hydrogen or oxygenated water. An ingenious memoir on the subject was published by him in 1818, in which the formation and the properties of this compound are fully detailed. I had no small satisfaction in 1822, when at Paris, in being obligingly favoured by M. Thenard with a view of the process of the formation, and of the more distinguishing properties of this singular liquid.

The nature of fluoric acid is still enveloped in obscurity. My experience led me to adopt the composition of fluate of lime to be 40 acid and 60 lime per cent. I had not then seen Scheele’s admirable essay on the subject. From the 5th section of his 2d. essay on fluor mineral, 1771, it may be deduced that fluate of lime is composed of 72.5 lime and 27.5 acid per cent. In 1809 Klaproth, and near the same time, Dr. Thomson found about 67½ lime and 32½ acid per cent. in fluor spar. They both erred, no doubt, as I did, by not repeating the treatment of the mineral with sulphuric acid often enough. Since then most authors, as Davy, Berzelius, Thomson, &c., agree with Scheele nearly, in assigning 27.5 acid, and 72.5 lime, in 100 parts of fluate of lime. My experience in 1820 gave me 1 per cent. less of lime; and Dr. Thomson now finds about 1 per cent. more of lime than Scheele’s analysis gives.

If we estimate the atom of lime at 24, that of fluoric acid must be about 9, according with the above proportion; this is much below 15, the weight of an atom of deutoxide of hydrogen.

Should Sir H. Davy’s view of fluate of lime be found correct, its atomic constitution would be one atom of calcium, the metallic substance of which lime is the protoxide, and one atom of fluorine, the name he has assigned to the other element, which with hydrogen is supposed to constitute the fluoric acid. The atom of fluor spar would then be 1 atom of calcium, 17, united to one atom of fluorine 16.

MURIATIC ACID.--OXYMURIATIC ACID, &c.

From the articles muriatic acid and oxymuriatic acid in the former volume, published now 16 years ago, as well as from the appendix to said volume, in which sundry animadversions are found on the fluctuating opinions entertained in regard to these acids, the reader will not be surprised to find some further addition.

Three notions have been submitted to the public in the last twenty years in regard to the nature of muriatic acid. First, the gas detached from common salt by sulphuric acid has been thought to be the acid in a state of purity, and constituted of a certain base or radical united to oxygen; this was the notion inculcated in the articles alluded to above. Second,--it is stated as a fact that when oxymuriatic acid and hydrogen in equal volumes are united by the electric spark, a volume of muriatic acid gas is the result equal to the sum of both the other volumes, and that this gas perfectly agrees with the gas obtained from common salt by sulphuric acid; this suggested the idea that muriatic acid gas is a compound of what has been called real or dry muriatic acid one atom, and water one atom. And, third, it is argued, that the element we have called oxymuriatic acid gas, is, for aught that appears, a simple body, and consequently, that muriatic acid gas is the real acid, and is constituted as above, of one atom of hydrogen, and one atom of oxymuriatic acid (now called chlorine.) It is not intended here to enter into a discussion of the arguments and facts adduced in support of the different conclusions. More experience must be had before all the doubts and difficulties are removed from the subject. But it will be proper to illustrate these different positions by an example. For instance, common salt, muriate of soda or chloride of sodium. By the first notion 50 parts of dry common salt will consist of one atom of muriatic acid gas, 22, and one atom of caustic soda, 28. By the second notion the same salt will be formed of 30 parts of muriatic acid gas, and 28 of caustic soda; but 8 parts of water evaporate when the salt is dried. By the third view common salt consists of oxymuriatic acid, or chlorine and sodium, or the metal of which caustic soda is the protoxide; and 50 parts of salt will consist of 29 chlorine and 21 sodium, or one atom of each.

NITRIC ACID--COMPOUNDS OF AZOTE AND OXYGEN.

Since the account of nitric acid (Vol. 1, page 343) was printed, a change has universally taken place in estimating the weight of the nitric acid atom, and of the proportion of azote and oxygen in the same. This has been effected chiefly by a more correct analysis of nitre than existed at that time. Nitre is now found to consist nearly of 52 parts acid and 48 parts potash per cent. Hence if the atom of potash be 42, that of nitric acid must be 45; for, 48 ∶ 52 ∷ 42 ∶ 45, nearly. That is, the nitric acid atom consists of 10 azote + 35 oxygen by weight; or of 2 atoms of azote (according to my estimate) and 5 of oxygen. There appear to be two nitrous acids; namely, the one which I have designated by that name, which may now be called subnitrous, or as Gay Lussac terms it pernitrous; and the other what I considered as nitric acid in the former volume, composed of 1 atom azote, and 2 of oxygen.

Real nitric acid then is that combination which is effected by uniting oxygen with a minimum of nitrous gas; or 1 measure of oxygen with 1.3 nitrous gas, (See Vol. 1, page 328). The oxynitric acid, which I was led to infer from the last mentioned combination, (1 azote with 3 oxygen) does not appear to exist. The Table of nitric acid (Vol. 1, page 355) will require some correction. An increase of about 4 per cent. should be made, I apprehend, on the quantities of acid corresponding to the several specific gravities.

Since my former volume of Chemistry was printed, several essays on the compounds of azote and oxygen have been published, with some new and some additional experiments, the chief of which may be seen in Sir H. Davy’s Elements of Chemical Philosophy, the Annales de chimie et de physique, Vol. 1; Annals of philosophy, Vol. 9 and 10; and the Manchester Society’s Memoirs, Vol. 4, second series; also Dr. Thomson’s first principles of Chemistry. Notwithstanding all that has been written on the subject, there still appears uncertainty as to the number of combinations formed by these two elements, their relative weights, and the number of atoms in the several compounds.

The results of an experiment I lately made on the decomposition of nitrate of potash by heat seem to be worthy of record, as I am not acquainted with those of any other person who has pursued the experiment to the same extent.--I took an iron retort of 6 cubic inches capacity, and cleaned it as well as I could from carbonaceous matter which it had previously contained, first by heating nitre to redness for an hour or more in it, and then washing it repeatedly with water till the liquid came out tasteless, and only mixed with a little red rust; I then put in 480 grains of purified nitre, and having secured a copper tube to the retort so as to be air tight, the retort was put into a fire and gradually raised to a red heat, and the fire was occasionally urged with a pair of bellows, in order to keep up a glowing red on the retort for nearly two hours; the air was received over water in jars; the first 4 or 5 inches were thrown away, and the rest was preserved and transferred to a graduated jar; the products were examined in successive portions as under, namely,

Inches. 1 produce, 85 cubic inches, 83 per cent. pure = 70.5 2 5 77 = 3.85 3 25 50 = 12.5 4 6 30 = 1.8 ----- ------- Total 121 Oxygen 88.65 Oxygen 88.65 = 30 grains. ------ Residue 32.35 = 10 grains.

About 1 per cent. on the whole gas was carbonic acid, the rest oxygen and azote, the weights of which would be nearly as above.

Towards the last the gas came very slowly, and being of inferior quality, the operation was discontinued.

The remaining contents of the retort were diluted with water, and well washed till the water ceased to shew alkali; the liquid was then concentrated and gave 1600 water grain measures of the sp. gr. 1.153. There were obtained also 64 grains of red oxide of iron from the washing of the retort, containing 19 grains of oxygen.

The liquid was divided into portions and examined; the original nitre consisted of 250 grains of nitric acid united to 230 of potash = 480 grains. After the process there appeared to be,

10 grains of carbonic acid united to 21 grains potash. 62 grains of subnitrous acid to 84 ” ” 134 grains nitric acid to 125 ” ” --- 230

The quantity of carbonic acid was determined by lime water: the quantity of potash uncombined with nitric acid was found by precipitating it by tartaric acid, and manifested 105 grains of potash in the bitartrate = that combined with the carbonic and subnitrous acids; from which subtracting 21, it was inferred the remainder 84 must have been in union with subnitrous acid, or else with nitrous acid; the rest of the potash, not being acted upon by tartaric acid, was understood to be combined with nitric acid.

The quantity of subnitrous acid given above, appeared somewhat hypothetical, till it was confirmed by treating a portion of the liquid with oxymuriate of lime solution of known strength; it was found that 32 grains of oxygen were required to be combined with the subnitrous acid, in order to restore it to the state of nitric acid; that is, when oxymuriate of lime, containing that quantity of oxygen, was added to the liquid, and this was afterwards rendered acidulous by the addition of sulphuric acid, neither nitrous vapour nor oxymuriatic gas was perceptible; but a greater or less quantity of the oxymuriate being applied, and the liquid made acidulous, the fumes of the one or the other were abundantly manifest.

It remains to account for the oxygen. There were 250 grains of nitric acid at first in the nitre; of which 200 grains were oxygen and 50 azote, nearly. One-fifth part of the oxygen = 40 grains, corresponds to 1 atom of oxygen. Now the whole of the oxygen derived from the nitre in the course of the experiment, seems to be 30 grains in gas, 7 grains in the carbonic acid, and 19 grains in the iron oxide, together equal to 56 grains. Now the azote and oxygen in the gas collected, were very nearly in the proportion of those elements in nitric acid; so that a portion of the acid (about ⅙) might be considered as completely decomposed, whilst the rest was only losing a small part of its oxygen: this is remarkable, and I think indicates that the carbonic acid (formed from the carbon of the retort, or from the adhering carbon) unites to the potash, expelling the nitrous acid, which is immediately decomposed into its elements azote and oxygen. This would not however account for the whole of the azote: for, 40 grains of nitric acid would be united to 37 potash; whereas we find only 21 potash with carbonic acid; and I cannot believe that an error in the estimate of carbonate of potash could exist to that amount. The fact, however, was, that the elements of 40 grains of nitric acid were found in the evolved gas, and hence we have to account for the remainder 210 grains. From this there appears to have been expelled 26 grains of oxygen, nearly 19 and 7 as related above; of which the 19 grains cannot be correctly estimated by reason of the uncertainty as to the real quantity of oxide formed during the operation: there might be some left adhering to the retort, or on the other hand there might be more than the due share, derived from former experiments. Supposing then, that 26 grains of oxygen were extracted from the nitric acid, the remaining acid would require the same to be added to re-form the nitric; but by the experiments with oxymuriate of lime it seemed to require 32 grains of oxygen. This difference wants an explanation; I believe the greater error must belong to the 26 grains; perhaps the truth might be approximated best by supposing both to be 30 grains.

When the liquid decomposed nitre is treated with any acid, a gas is instantly expelled which produces red fumes in the air; it is pure nitrous gas, which joining with the oxygen of the atmosphere, generates nitrous acid vapour. At the same time, no doubt, the subnitrous acid is disengaged from the potash, but that part of it which is real nitrous acid (1 atom azote to 2 of oxygen) is retained by the water, whilst the other part, (1 atom azote and 1 of oxygen) assumes the gaseous form. In order to be satisfied respecting this point, I made several experiments with the liquid over mercury: taking a given portion of the liquid, and sending it to the top of a graduated tube filled with mercury, I passed up as much muriatic acid as was sufficient to engage the potash; immediately there was a disengagement of nitrous gas and carbonic acid gas, and afterwards a slow evolution of gas, evidently arising from the liquid in contact with the mercury. Wishing to ascertain the quantities, I sent up 25 grain measures of liquid, and to that nearly half its bulk of muriatic acid; in 2 or 3 minutes there was,

1.1 cubic inch of gas. H. M. 1.4 in 0 45 1.5 1 5 1.7 2 45 1.75 7 45 1.78 9 45

The gas was washed in lime water, and lost .33 parts of an inch of carbonic acid; the rest, 1.45 cubic inch, was nitrous gas. It is obvious that ½ of the nitrous gas, together with the carbonic acid, was liberated instantly; the rest of the nitrous gas was due to the nitrous acid, slowly acting upon the mercury. At the end of the process, there was a little black oxide floating upon the mercury. Calculating from this, the whole quantity of nitrous gas would be 31 or 32 grains, whereas it ought to have been 48 grains to constitute 62 of subnitrous acid. It is probable that whilst a portion of the subnitrous acid is oxidizing the mercury, another portion may be forming nitric acid and dissolving the oxide.

From some trials, I have reason to think that even carbonic acid will expel nitrous gas from the liquid sub-nitrite of potash.

In the essay of Dr. Henry, already alluded to, published in the 4th Vol. of the Manchester Society’s Memoirs, a new and interesting discovery is made; namely, that a mixture of nitrous and olefiant gases, though not explosive by an electric spark, may still be exploded by the more powerful impetus of a shock from a charged jar. Dr. Henry has adduced the results obtained in this way, as corroboratory of those which shew the constitution of nitrous gas to be 1 volume of azote and 1 of oxygen united to form 2 volumes of nitrous gas. (See page 507 of the Memoirs.)

Some time ago in repeating these experiments of Dr. Henry, I found some extraordinary circumstances attending them. After determining that 1 volume of olefiant gas may be fired with from 6 to 10 volumes of nitrous, I found a shock from a jar sometimes inadequate to fire the mixture, which, however, when repeated a second or third time, succeeded. This is not a novelty; for, mixtures of olefiant gas as well as other gases and vapours, with a minimum of oxygen, frequently require several sparks before the explosion: but this case occurs at times with nitrous and olefiant gas, when they are mixed in the most favourable proportions for exploding. The most remarkable circumstance, however, was, that when a phial was filled with the mixture of the two gases in the proportion of 1 volume olefiant to 6 or 7 nitrous, (exclusive of small portions of azote), the decomposition of the nitrous gas and the combustion of the olefiant were scarcely ever perfect; and what increased the perplexity more, was, the results obtained from the same mixture scarcely ever agreed one with the other. After about 30 experiments, I was inclined to adopt the conclusion, that the uncertainty was occasioned by the oblong form of the eudiometer. The spark or shock, in my eudiometer, is imparted at one extremity of a column of air, which is often 10 times as much in length as in diameter: it mostly was found that the larger the quantity of mixture exploded at once, the more imperfect and incomplete was the combustion. I imagine the intensity of heat is not sufficient to carry on the combustion through the length of the column, owing, perhaps, to the cooling power of the sides of the tube. Hence it was, I apprehend, that in one or two instances, when a small quantity of gas was used, I got nearly complete results, as Dr. Henry reports his; but in the majority both gases were found in the residue after the explosion.

In pursuing this enquiry into the decomposition of nitrous gas by combustible gases, I found that it might be effected by any combustible gas or vapour: at least it succeeded in all I tried. The method I pursued, and which was suggested by the known properties of phosphuretted hydrogen, is this: it has been shewn (page 181) that a mixture of phosphuretted hydrogen and nitrous gas exploded by an electric spark, the former gas being completely burned in case the proportions are duly adjusted; now, it occurred to me, that as the above combustible gas is usually a mixture of pure phosphuretted hydrogen and of hydrogen, and that the latter of these is also burned as well as the former, the effect must be produced through the heat occasioned by the combustion of the former. Having some old phosphuretted hydrogen by me, at the time, which on examination, I found to be 91 per cent. combustible gas, and 9 azote; and the 91 combined with 156 of oxygen, consequently was 74 pure, and 17 hydrogen; I tried this mixture with nitrous gas, when it exploded by the spark, as usual; but on trying it with an excess or defect of nitrous gas, the spark was inefficient, but the shock instantly fired the mixture. As there did not appear to be any of the pure hydrogen left unburned in these experiments, I proceeded to mix the old phosphuretted hydrogen with hydrogen; and then this new mixture with nitrous gas. The first experiment was made with 4 parts of old phosphuretted hydrogen + 16 hydrogen + 36 nitrous gas = 56 total. On this mixture the spark, of course, had no effect; but it exploded the first trial by the jar, and left 20 measures, of which 2 were found to be oxygen, and the rest azote. This experiment succeeding so well, I next tried mixtures of phosphuretted hydrogen, with carbonic oxide, carburetted hydrogen, and ether vapour successively, along with nitrous gas; and found that all these mixtures refused combustion by the spark, but were instantly exploded by the shock, yielding carbonic acid and water, the same as if the combustion had been effected by free oxygen. In some instances the combustion was complete, leaving neither combustible gas nor nitrous gas; but generally there was a residue of one or both of the gases.

From these experiments it may be concluded that the heat, produced by the combustion of phosphuretted hydrogen and nitrous gas or oxygen gas, disposes other gases, accidentally in the mixture, to chemical changes. In conformity with this view, I mixed phosphuretted hydrogen and oxygen, in the proportion of mutual saturation; and taking a small proportion of this mixture, and as much ammoniacal gas as would saturate the phosphoric acid to be formed, I found that causing an explosion over mercury, the phosphoric acid combined with the ammonia, and nearly the whole gas disappeared. In this case, the heat was not sufficient to decompose the ammonia. But in another experiment, with a portion of the same explosive mixture and a less proportion of ammonia, after the firing a residue of azote and hydrogen was found, amounting nearly to the quantity due from the decomposition of the ammonia. Here the heat produced, had evidently decomposed the ammonia.

ON AMMONIA.

The constitution of ammonia still remains undecided. The latest experiments on this article are those of Dr. Henry, in his essay on the analysis of the compounds of nitrogen. (Memoirs of the Manchester Society, vol. 4, 1824.) By electrifying ammoniacal gas over mercury, as carefully as could be devised, Dr. Henry found results as under:

1st experiment 44 measures became 88+ 2d 157 320 3d 60 122 4th 120 240

The evolved gases carefully analysed by combustion with oxygen, were found to consist of 3 volumes of hydrogen and 1 of azote. The analysis of ammonia was also effected by exploding it with nitrous oxide, with the requisite precautions. The results confirmed the previous ones by electricity, both in regard to doubling the volume of ammonia, and establishing the ratio of 3 to 1 in the volume of hydrogen and azote.--These experiments are highly interesting as far as regards the question of ammonia, as they exhibit the latest investigations of one who has previously shewn uncommon skill and perseverance in this kind of analysis. (See Philos. Transact. 1809, &c.)

Dr. Henry’s analysis of ammonia, in 1809, has been adverted to in our article on the subject, vol. 1, page 429. The results of that Essay are given in a tabular form; and the mean of six experiments was nearly as we have stated, namely, that ammonia consists of 27¼ measures of azote, and 72¾ hydrogen. To this it may be proper to add, that the two extremes were, 26.1 azote and 73.9 hydrogen, and 28.2 azote with 71.8 hydrogen; also that a small error has crept into the table, which being corrected, the average results are reduced to 27 and 73, very nearly. Subsequently, both Dr. Henry and Sir H. Davy concurred in assigning 26 and 74 for the most approximating numbers. (See Nicholson’s Journal, 25, page 153). The true quantity of gases procured by the decomposition of ammoniacal gas by electricity, was concluded by both these authorities, to be 180 for each 100 of ammonia, when the requisite precautions were taken, as we have related in vol. 1.

From what is stated above, it is evident the subject is one which requires extraordinary skill and attention. This I can attest from my own experience, which has been frequently renewed and varied; but the results have not been sufficiently accordant to yield me satisfaction.

About ten years ago, I made several experiments on the decomposition of ammonia, which, though they are not convincing, deserve, perhaps, to be recorded in their results.--Some more recent experiments are incorporated with them.

Decomposition of ammonia by nitrous oxide.--I made many experiments, by exploding mixtures of nitrous oxide and ammoniacal gases over mercury. The excess of gas was mostly on the side of ammonia, but the proportions were varied in the different experiments, from 10 vol. nitrous oxide to 11 ammonia or to 5, which are about the extremes capable of being fired by the electric spark.

When 10 parts nitrous oxide and 5 of ammonia are exploded over mercury, the residuary gas contains some free oxygen and some nitrous acid derived from the decomposition of the excess of nitrous oxide used; with 6 parts of ammonia there is rarely any free oxygen. When 10 parts of nitrous oxide, and 7 of ammonia are fired, I never found any free oxygen or hydrogen; but when the ammonia is at or near 8 parts, I find from ¹/₂₀ to ⅒ of the hydrogen from the ammonia in the residuary gases. The two gases appear to be completely decomposed; the oxygen of the nitrous oxide, as far as it can, unites with the hydrogen of the ammonia, without forming any portion of nitrous acid or of free oxygen, and the residue contains the azote of both gases, and the unburnt hydrogen from the ammonia, as Dr. Henry first observed. This continues to be the case till the ammonia becomes 11 parts, when the hydrogen amounts to about ⅓ of the whole quantity which the ammonia yields.

From the above it would seem that the proportions for mutual saturation must be 10 nitrous oxide with from 7 to 8 parts of ammonia. This agrees with the deduction in Dr. Henry’s first essay that 13 nitrous oxide require 10 of ammonia; or that 10 require 7.7: but according to the theory of volumes 10 would require 6⅔; and Dr. Henry recommends in his late essay 10 nitrous oxide to 7.7 or 8⅓ parts of ammonia, in order to secure a small excess of the last, and consequently some free hydrogen after the explosion. The former of these proportions would have nearly ⅐ of the residue hydrogen, and the latter nearly ⅕, supposing the gases pure originally. This gives more hydrogen than I have ever found; but the azote in my experience nearly agrees with the doctrine of multiple volumes.

Decomposition of ammonia by nitrous gas.--About 30 experiments carefully made on mixtures of nitrous gas and ammoniacal gas gave very discordant results. At one time 10 parts nitrous gas with 14 ammonia gave ⅓ of hydrogen in excess, and another time 10 nitrous with 12 ammonia gave excess of hydrogen = ⁹/₂₀; generally 10 parts with 6 or less gave oxygen, and 10 with 8 or more gave hydrogen in the residue.

Decomposition of ammonia by oxygen.--The limiting proportions of oxygen and ammonia which I have fired, are 10 oxygen to 4 ammonia for the minimum, and 10 oxygen to 22 ammonia for the maximum. When 10 oxygen were fired with 4 ammonia, there were ²⁵/₃₇ of the oxygen left, and there was a deficiency of azote amounting to ¹/₁₂ of what was expected from the ammonia, owing no doubt to nitrous acid generated by the explosion. When 10 oxygen to 1.8, or from that to 2.2 ammonia are used, there is a surplus of about ¼ or ⅓ of the hydrogen contained in the ammonia, left in the residue of the gas. When the ammonia is between 13 and 14 there is usually a trace of oxygen or hydrogen as it approaches either of these limits. By the theory of volumes, 10 oxygen should saturate 13⅓ of ammoniacal gas. I have not any instance of hydrogen being left when 14 ammonia were used, though there ought to be ¹/₂₀ of the whole left; and much smaller quantities than that are appreciable by well known methods. The azote resulting from the decomposition of ammonia is usually very nearly ½ the volume of the ammonia.

On the whole the results from firing ammonia and oxygen gas appear to me more satisfactory than those obtained from nitrous oxide and nitrous gas, as they are more simple and less perplexed with any theoretic views.

It may be proper to remind the reader that when we speak of 10 parts of one gas uniting with 8, 10, or more, of another in the above and other cases, it is to be understood of gases absolutely pure; not that we ever obtain them in that state, but approximating as near as we can to it, we mix given portions of such gases as we can obtain, and then in our calculations of results deduct for the impurities.

One source of uncertainty in these experiments on firing mixtures of ammonia, is that the real quantity of ammoniacal gas operated upon is not known. If a certain measure of ammonia be transferred through mercury ever so dry, some portion of it gets entangled in the mercury, and 100 measures become perhaps 95: now in the explosion it is a question whether any part of the 5 measures absorbed is decomposed. I have marked this attentively, and am persuaded that generally speaking, little if any of that portion is decomposed; but some trace of it appears mostly afterwards in the residue as it is liberated from the pressure of its own kind of gas, and hence easily rises into the gaseous mixture. Notwithstanding, when the loss of gas by transfer amounts to 10 or 20 per cent., I have reason to believe that some part of it suffers combustion occasionally.

Volume of gases from the decomposition of ammonia.--It has been observed (vol. 1. Ammonia) that Sir H. Davy obtained 180 measures of gases, by means of electricity, from 100 of ammonia as the maximum when the operation was performed with great care, and Dr. Henry in like circumstances, produced 181, whilst I found 187 measures; since that, as has been related, Dr. Henry has found 200 measures. It is not easy to account for these differences; I am inclined to the opinion that the volume of gases is very nearly doubled, but probably rather less than more. I find the experiments on the rapid combustion of ammonia agree best with that opinion.

Decomposition of ammonia by a red heat.--A short time since I repeated the decomposition of ammonia by passing the gas through a red hot copper tube. The proportion of azote to hydrogen, due allowance being made for a minute portion of atmospheric air, was upon the average of a number of experiments, 26 of the former to 74 of the latter.

Decomposition of ammonia by oxymuriatic acid.--I have made several experiments on this mode of decomposition since the results published in vol. 1, page 435. It is well known that a solution of oxymuriate of lime decomposes ammoniacal salts; water and muriatic acid are produced, azote liberated, and the acid previously combined with the ammonia is evolved. But this is not all; an excessively pungent gas or perhaps vapour is produced, exciting sneezing, and inducing catarrh; the constitution of this vapour is not well understood; it is never formed, as far as I know, without the presence of both oxymuriatic acid and ammonia. The results of such mixtures are of course complicated and likely to be unsatisfactory; it may notwithstanding be useful to relate some of them.

When clear oxymuriate of lime solution, and a salt of ammonia are mixed together with a little excess of oxymuriate, the ammonia is mostly decomposed, the oxymuriate being converted into muriate of lime by the hydrogen of the ammonia, whilst the azote is evolved, and the acid previously combined with the ammonia is liberated; hence oxymuriatic acid gas is also liberated along with the azote; and it is required to be taken out before the azote can be estimated. This circumstance may be obviated by previously adding the requisite quantity of pure potash or soda, to engage the acid, or by leaving a little undissolved lime in the oxymuriatic solution. I could never obtain a volume of azote equal to half that of the ammonia (supposed to be in a gaseous state) though it is universally allowed not to be less than that, if the whole of the azote be evolved; on one occasion only I got so much as ¹⁴/₁₅ of that quantity. The residue of liquid has the extremely pungent smell; but the azotic gas after passing through pure water has no smell. When this experiment is made over mercury, the oxymuriatic acid acts upon it, and hence the excess of oxymuriate should be such as to leave a portion of that undecomposed at the conclusion.

When the object is to ascertain the hydrogen in ammonia, a portion of salt known to contain a given weight of ammonia is to be treated with oxymuriate of lime solution, the strength of which is accurately determined by means of green sulphate of iron, or otherwise. The ammoniacal salt in solution is then to be mixed with a moderate redundance of the oxymuriate liquid, and with a few drops of caustic potash, and the mixture must be repeatedly agitated for some time. At length the liquid must be tested by the green sulphate of iron, and hence the quantity of acid spent upon the ammonia will be determined. I have mostly found the hydrogen this way below the common estimate, allowing the ammoniacal salts to be correctly determined.

SULPHURET OF CARBON.

Since the article at page 462, vol. 1, was written, an excellent essay on the sulphuret of carbon has been published in the Philosophical Transactions, (1813) by Professor Berzelius and Dr. Marcet. After an extensive series of experiments, they infer the atom of the sulphuret to consist of 2 atoms sulphur and 1 of carbon. The investigation did not seem to warrant their including hydrogen in the atom. I have made several experiments on the combustion of the vapour of sulphuret of carbon in oxygen gas by electricity. My method generally was, to vapourize a given portion of atmospheric air over mercury, taking care that the vapour was below the maximum for the temperature; this is easily effected by putting the liquid into a phial of air, drop by drop, and inverting it over mercury till the liquid is evaporated. This vapourized air, I find may be transferred through mercury with very little loss, and even through water several times, without a total condensation of the vapour. The vapour of ether is much more condensible by water than that of sulphuret of carbon. A given portion of this vapourized air is to be mixed with oxygen gas, in Volta’s eudiometer, and then exploded by the electric spark over mercury. One volume of vapour combines with nearly 3½ of oxygen, and therefore requires 4 or 5 times its bulk of that gas before firing, in order that the combustion may be complete. The results of the combustion are carbonic acid and sulphurous acid; and I suspect a small portion of water; though Professor Berzelius and Dr. Marcet could not detect any.

By evaporating a given weight of the sulphuret of carbon, in a given volume of atmospheric air, at the temperature of 60°, I find the specific gravity of the vapour to be 2.75 nearly, air being 1. Now if we assume the atom of vapour to be nearly of the same volume as that of hydrogen, and to consist of 1 atom hydrogen, 2 sulphur, and 1 carbon, it will require 7 atoms of oxygen to form water, sulphurous acid, and carbonic acid, which will accord very well with my experience. When vapourized hydrogen gas is electrified for some time, there is no change of volume, though there is some appearance of decomposition. Probably the hydrogen of the sulphuret is liberated. It is difficult to conceive how so volatile a liquid as the one in question, could be constituted out of sulphur and carbon without the addition of hydrogen.

POTASSIUM, SODIUM, &c.

Two views of the nature of these bodies have been given in vol. 1, (see pages 260, and 484, &c.). In the former they are considered as simple metals; in the latter, as compound bodies resulting from the abstraction of oxygen from the hydrates of potash and soda; or as being constituted of 1 atom of hydrogen united to 1 atom of pure potash or soda respectively. Those who have had the most experience on these elements, Sir H. Davy, and M. M. Gay Lussac and Thenard, seem now to concur in the former view, and it has been adopted by most chemists. Part of the objections which we made to this view have been obviated, it should seem, by establishing the fact, that oxymuriatic gas and hydrogen gas united, form muriatic acid gas. There are still, however, difficulties to remove before this view can be considered perfectly satisfactory; but they are not greater perhaps than would attach to any other explanation of the facts connected with the subject. Besides potassium and sodium, experience as well as analogy would seem to render probable, if not to establish, the existence of barium, strontium, and calcium as metals, of which barytes, strontites, and lime are the protoxides, as potash and soda are of the other two metals; (other oxides of potassium and sodium are stated, see page 55-57); barium has a deutoxide, and probably calcium likewise. The rest of the earths, as magnesia, alumine, silex, &c. are by analogy considered by most chemists as oxides of particular metals, but the proportions of their elements have not been determined.

ALUM.

At page 531, vol. 1, we have given the constitution of this important salt, as under: since that time Mr. R. Phillips has announced another view of it; and Dr. Thomson has published one differing from both of these. They are as follow:

Dalton-- 1 atom sulphate of potash. 4 atoms sulphate of alumine. 30 atoms water.

Phillips-- 1 atom bisulphate of potash. 2 atoms sulphate of alumine. 22 atoms water.

Thomson-- 1 atom sulphate of potash. 3 atoms sulphate of alumine. 25 atoms water.

Notwithstanding these differences, there is a near approximation in all three, in regard to the quantities of acid, alumine, potash, and water in the salt. This is accounted for partly in the different relative weights of the atoms, as estimated by the different analysts, but chiefly in that of alumine.

Some very curious results occurred to me about 10 years ago in analysing alum; they were new to me, but I have since found they had been previously discovered by Scheele. (See his essay on silex, clay, and alum, 1776.) As his observations are not to be found in any of our elementary books that I have seen, I shall give the particulars of my own experiments here.

I take 24 grains of alum and dissolve them in water; of these 8 grains may be allowed for sulphuric acid, ⅕ of which = 1.6 grain = 1.1 grain of lime = 880 grains of lime water, such as I commonly use. To the solution of alum I put 880 grains of lime water; a slight precipitate appears which soon becomes redissolved almost completely. The liquid is then acid by the colour test.

To this liquid I put 880 more of lime water, and agitate; a copious precipitate appears and continues; after subsidence the clear liquid is still acid by the colour test.

Another 880 grains are added, and the whole is then well agitated; the agitation is repeated two or three times after the precipitate has partly subsided, so as to diffuse it equally again through the liquid; finally, the clear liquid is found to be neutral by the colour test, and to contain no alumine; for, lime water produces no precipitate when poured into it.

Another 880 grains being added, and the whole stirred well, the clear liquid after the subsidence of the precipitate is still neutral by the colour test.

The fifth portion of 880 grains being then added, and the mixture well agitated, a considerable portion of the precipitate will evidently disappear, and the mixture become semitransparent; after a time the clear supernatant liquid is found strongly alkaline; a little of it touched with an acid becomes milky, and adding more acid clears it again. The liquid is now 1.0025 sp. gr., or a little heavier than lime water.

The sixth portion of 880 grains being now added to the whole mixture, and agitated, the precipitate rather diminishes, and an increase of specific gravity takes place in the liquid; it is now 1.003.

The seventh and last portion of 880 grains being added to the mixture, and agitation being continued for some time, a dense bulky precipitate is formed, which falls with great celerity, carrying with it the greatest part of the acid, the alumine and the lime, and leaving the liquid of the sp. gr. 1.0012. It is a subsulphate into which acid, potash, lime and alumine enter, as will be shewn.

These phenomena appear to me to be best explained by adopting a constitution of alum, such as to make it consist of 1 atom bisulphate of potash and 3 atoms of sulphate of alumine; after which the following explanation will apply.

The first portion of lime water saturates the excess of acid.

The second portion throws down a correspondent portion of alumine. The clear liquid is acid, because it contains sulphate of alumine, which is essentially acid by the colour test, because alumine is not an alkaline element.

The third portion throws down another portion or atom of alumine; but by continued agitation the two atoms of alumine liberated, join the remaining atom of sulphate of alumine, and the whole compound falls down, being then the common subsulphate of alum. Hence the liquid, containing nothing but sulphate of lime and sulphate of potash, is neutral by the test, and yields no alumine by the addition of lime water.

The fourth portion of lime water being put in and duly agitated, the atom of sulphuric acid is drawn from the subsulphate to join the lime, and then the floating subsulphate of alumine becomes pure alumine, and the clear liquor is still neutral.

The fifth portion of lime water tries to decompose the sulphate of potash, but is unable of itself; however, the floating alumine assists it, and by double affinity the potash leaves the acid to join the alumine, and the lime takes the acid. Hence as ⅓ of the alumine enters into solution with the potash, the precipitate is less copious, and the liquid is alkaline; a small portion of acid put into the clear liquid engages the potash, and liberates the alumine, but a larger portion redissolves the alumine also.

The sixth portion of lime water seems to complete the effect which the fifth commences, and hence the density of the liquid increases, whilst the precipitate rather diminishes.

The seventh portion of lime, together with the sixth, after due agitation and some time, unite the lime with the alumine, one atom of each, and form a precipitate which would fall together, were no other compound present, as I found, and Scheele before me; but if sulphate of lime be present, each compound atom of lime and alumine, unites with one of sulphate of lime, and the whole descends together, forming a subsulphate resembling that of alum, only two atoms of lime are found as substitutes for two atoms of alumine. This subsalt is very little soluble in water.

According to this view, if 2 atoms of alum were decomposed, 4 atoms of subsulphate would be formed, each consisting of 1 acid, 2 lime, and 1 alumine; also 2 compound atoms of potash and alumine, and 6 atoms sulphate of lime. But in the final arrangement, it would seem, that 2 atoms of sulphate of lime are again decomposed, and sulphate of potash formed, the 2 atoms of lime combining with the 2 of alumine, and then two more atoms of subsulphate are formed, and the final arrangement is 6 atoms subsulphate precipitated, and 2 atoms sulphate of potash, and 2 sulphate of lime remain in solution.

The facts above stated appear to me to place the constitution of alum in a clearer point of view than any other I have seen. They make no difference in the weights of the several elements in 100 grains of the salt, from what we have given in Vol. 1; only the weight of the atom of alumine is here taken to be 20 instead of 15, and we have 3 atoms of it in 1 of alum, instead of 4, as in the former account.

ON THE PRINCIPLES OF THE ATOMIC SYSTEM OF CHEMISTRY.

It is generally allowed that the great objects of the atomic system are, 1st to determine the relative weights of the simple elements; and 2d to determine the number, and consequently the weight, of simple elements that enter into combination to form compound elements. The greatest desideratum at the present time is the exact relative weight of the element hydrogen. The small weight of 100 cubic inches of hydrogen gas, the important modifications of that weight by even very minute quantities of common air and aqueous vapour, and the difficulties in ascertaining the proportions of air and vapour in regard to hydrogen, are circumstances sufficient to make one distrust results obtained by the most expert and scientific operator. The specific gravity of hydrogen gas was formerly estimated at ⅒ that of common air; it descended to ¹/₁₂.₅, which is the ratio we adopted in the Table at the end of Vol. 1. it is now commonly taken to be ¹/₁₄.₅, and whether it may not in the sequel be found to be ¹/₁₆.₅ is more than any one at present, I believe, has sufficient data to determine. The other factitious gases have mostly undergone some material alterations in their specific gravities in the last twenty years, several of which I have no doubt are improvements; but when we see these specific gravities extended to the 3rd, 4th, and 5th places of decimals, it appears to me to require a credit far greater than any one of us is entitled to. In the mean time, it may be thought a fortunate circumstance, that the weight of common air has undergone no change for the last thirty or forty years; 100 cubic inches bring estimated to weigh 30.5 grains at the temperature of 60°, and pressure of 30 inches of mercury: (whether this is exclusive of the moisture I do not recollect.) It is also a fortunate circumstance, (provided it be correct) that this weight is nearly free from decimal figures. I may be allowed to add, that according to my experience, the weight of 100 cubic inches of air is more nearly 31 grains than 30.5. I apprehend these observations are sufficient to shew that something more remains to be done before we obtain a tolerably correct table of the specific gravities of gases; the importance of this object can not be too highly estimated.

The combinations of gases in equal volumes, and in multiple volumes, is naturally connected with this subject. The cases of this kind, or at least approximations to them, frequently occur; but no principle has yet been suggested to account for the phenomena; till that is done I think we ought to investigate the facts with great care, and not suffer ourselves to be led to adopt these analogies till some reason can be discovered for them.

The 2d object of the atomic theory, namely that of investigating the number of atoms in the respective compounds, appears to me to have been little understood, even by some who have undertaken to expound the principles of the theory.

When two bodies, A and B, combine in multiple proportions; for instance, 10 parts of A combine with 7 of B, to form one compound, and with 14 to form another, we are directed by some authors to take the smallest combining proportion of one body as representative of the elementary particle or atom of that body. Now it must be obvious to any one of common reflection, that such a rule will be more frequently wrong than right. For, by the above rule, we must consider the first of the combinations as containing 1 atom of B, and the second as containing 2 atoms of B, with 1 atom or more of A; whereas it is equally probable by the same rule, that the compounds may be 2 atoms of A to 1 of B, and 1 atom of A to 1 of B respectively; for, the proportions being 10 A to 7 B, (or, which is the same ratio, 20 A to 14 B,) and 10 A to 14 B; it is clear by the rule, that when the numbers are thus stated, we must consider the former combination as composed of 2 atoms of A, and the latter of 1 atom of A, united to 1 or more of B. Thus there would be an equal chance for right or wrong. But it is possible that 10 of A, and 7 of B, may correspond to 1 atom A, and 2 atoms B; and then 10 of A, and 14 of B, must represent 1 atom A, and 4 atoms B. Thus it appears the rule will be more frequently wrong than right.

It is necessary not only to consider the combinations of A with B, but also those of A with C, D, E, &c.; as well as those of B with C, D, &c., before we can have good reason to be satisfied with our determinations as to the number of atoms which enter into the various compounds. Elements formed of azote and oxygen appear to contain portions of oxygen, as the numbers 1, 2, 3, 4, 5, successively, so as to make it highly improbable that the combinations can be effected in any other than one of two ways. But in deciding which of those two we ought to adopt, we have to examine not only the compositions and decompositions of the several compounds, of these two elements, but also compounds which each of them forms with other bodies. I have spent much time and labour upon these compounds, and upon others of the primary elements carbone, hydrogen, oxygen, and azote, which appear to me to be of the greatest importance in the atomic system; but it will be seen that I am not satisfied on this head, either by my own labour or that of others, chiefly through the want of an accurate knowledge of combining proportions.

NEW TABLE OF THE RELATIVE WEIGHTS OF ATOMS.

At the close of the last volume, the weights of several principal chemical elements or atoms were given; but as several additions and alterations have been educed from subsequent experience, it has been judged expedient to present a reformed table of weights.

SIMPLE ELEMENTS.

Weights. Hydrogen 1 Azote 5±, or 10? Carbone 5.4 Oxygen 7 Phosphorus 9 Sulphur 13, or 14 Calcium 17? Sodium 21 Arsenic 21 Molybdenum 21, or 42? Cerium 22? Iron 25 Manganese 25 Nickel 26 Zinc 29 Tellurium 29, or 58? Chromium 32 Potassium 35 Cobalt 37 Strontium 39 Antimony 40 Iridium 42 Palladium 50 Uranium 50, or 100? Tin 52 Copper 56, or 28? Rhodium 56 Titanium 59? Gold 60± Barium 61 Bismuth 62 Platina 73 Tungsten 84, or 42? Silver 90 Lead 90 Columbium 107? 121? Mercury 167, or 84?

SIMPLE OR COMPOUND?

Weights. Fluoric Acid 10? 15? Magnesia 17 Alumine 20 Glucine 23? 34? Lime 24 Oxymuriatic Acid (chlorine) 29, or 30 Muriatic Acid} 30, or 31 Gas} Zircone 45 Silex 45? Yttria 53? 36? 18?

COMPOUND ELEMENTS.

Weights. Ammonia 6? 12? 13? Olefiant Gas 6.4? 12.8? Carburetted Hydrogen or Pond Gas 7.4 Water 8 Phosphuretted Hydrogen 10 Nitrous Gas 12, or 24? Carbonic Oxide 12.4 Sulphuretted Hydrogen 15 Deutoxide of Hydrogen 15 Nitrous Oxide 17 Nitrous Acid 19, or 38? Carbonic Acid 19.4 Sulphurous Oxide 21 Phosphoric Acid 23 Sulphurous Acid 28 Protoxide of Arsenic 28 Soda 28 Hydrate of Lime 32 Protoxide of Iron 32 Protoxide of Manganese 32 Protoxide of Nickel 33 Sulphuric Acid 35 Sulphuret of Arsenic (native) 35 Hydrate of Soda 36 Oxide of Zinc 36 Carbonate of Magnesia 36.4 Protosulphuret of Iron 39 Deutoxide of Manganese 39 Oxide of Chromium 39 Muriate of Magnesia 39 Protosulphuret of Nickel 40 Protosulphuret of Lime 41 Carbonate of Lime 43.4 Protoxide of Cobalt 44 Strontites 46 Muriate of Lime 46 Chromic Acid 46 Protoxide of Antimony 47 Carbonate of Soda 47.4 Hydrate of Potash 50 Muriate of Soda 50 Sulphate of Magnesia 52 Sulphuret of Antimony 54 Sulphate of Alumine (simple) 55 Oxide of Palladium 57 Sulphate of Lime 59 Protoxide of Tin 59 Carbonate of Potash 61.4 Hydrosulphuret of Antimony 62 Nitrate of Magnesia 62 Sulphate of Soda 63 Protoxide of Copper 63 Muriate of Potash 64 Deutoxide of Tin 66 Protosulphuret of Tin 66 Oxide of Gold 67 Barytes 68 Muriate of Lime 69 Oxide of Bismuth 69 Deutoxide of Copper 70 Nitrate of Soda 73 Sulphuret of Gold 74 Protosulphuret of Bismuth 76 Sulphate of Potash 77 Oxide of Platina 80? Nitrate of Potash 87 Carbonate of Barytes 87 Muriate of Barytes 90 Oxide of Silver 97 Protoxide of Lead 97 Minium 98 Sulphate of Barytes 103 Deutoxide of Lead 104 Protosulphurets of Lead and Silver 104 Nitrate of Barytes 113 Protoxide of Mercury 174? Deutoxide of Mercury 181? Protosulphuret of Mercury 181 Alum 277

ADDENDA.

STEEL.--Since writing the article at page 214, I have had an opportunity of analysing the crystalline steel, formed by Mr. Macintosh’s process of cementation by means of coal gas. I dissolved 21 grains of this steel in sulphuric acid, with only a very slight excess of acid. The whole was dissolved except about ⅒ of a grain of silvery-like particles. The gas obtained amounted to 29.6 cubic inches. It yielded no trace of carbonic acid. When fired with oxygen it yielded 3 per cent. upon the volume of hydrogen of carbonic acid; and this arose, as I ascertained, from the hydrogen containing 3 per cent of carburetted hydrogen gas: it contained no carbonic oxide. Supposing the carbone to have been combined with the iron, it would amount only to about ⅝ of a grain, to 100 grains of iron. Whether such a quantity can be deemed an essential or an accidental ingredient of steel, may be a subject of consideration.

By a mistake of the Printer, the following paragraphs were omitted after page 308.

EXAMPLE.

According to the following values of the different specific gravities, (of the accuracy of some of which there may be doubts) and referring to my essay on oil gas (Manchester Memoirs, Vol. 4, new series, page 79,) we may take the oil gas, which, when the incombustible portion was abstracted would be nearly .812 sp. gravity, and

100 pure gas give 152 carb. acid and take 248 oxygen;

Here w = 100, a = 152, g = 248, S = 1.458, ∫ = .555, c = .972 s = .0694 and C = .812. The value of u reduces to the following form;

u = 4.7916a - 1⅔g + 1.875w - 6Cw -------------------------------------------- = 24.5 .625

hydrogen per cent. of pure combustible gas.

Hence we have 75.5 volumes left for the 3 other ingredients = w of the formula; and abstracting 12 + from the oxygen on account of the hydrogen, g = 236, and a = 152 as above.

Whence x = Superolefiant = 38¼ y = Carb. hydrg. = 30.2 and z = Carb. oxide = 7+ ----- 75.5

These results differ considerably from those deduced in the above essay; probably in part from errors in the above estimates of the specific gravities of one or more of the gases.

EXPANSION OF LIQUIDS BY HEAT.

I am not aware of any particular labour that has recently been given to the enquiry how far pure liquids accord with each other in the law which I announced as derived from the experiments on water and mercury, and corroborated by those upon several other liquids. See Vol. 1, Table of temperature, page 14; also page 36, and following.

Perhaps all liquids should be considered as pure that are subject to uniform congelation at certain temperatures on the one hand, and on the other are capable of being distilled by heat without any alteration in their constitution. Water and mercury will rank in the first place; alcohol of .82 specific gravity and ether of .72; concentrated sulphuric acid; nitric acid of 1.42 specific gravity: naphtha and oil of turpentine, &c. will probably be thought to claim the next place. It is desirable that the temperatures at which these liquids congeal should be ascertained; also whether any decomposition is effected by the operation. If these expand proportionally to a scale of square numbers for certain given equal or unequal intervals of temperature, it may point out something relative to the collocation of the ultimate particles in liquids. The apparent coincidence of this rate of expansion in liquids, with the geometrical progressive force of steams or vapours creates an additional interest. It may be that most or all of these supposed relations are accidental, and only approximative like that of the rate of expansion of air and mercury, between the temperatures of -40° and 212°; but I cannot think this probable. Even should they be only approximations, they are of sufficient utility to be kept in view.

FINIS.

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