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.[20] This compound
is hard and extremely tenacious, exceeding in this respect any other
alloy of the two metals. The addition or subtraction of 1 or 2 parts of
tin materially impairs the tenacity of the alloy. It is constituted of
8 atoms of copper and 1 of tin.
[Footnote 20: See a very excellent essay on the alloy of copper and tin
by M. Dussaussoy, in the Annales de Chimie & Physique. 5--113.]
(_b_). _Alloy for edge tools, printers’ cylinders, &c._ The best
proportion for this compound seems to be 100 parts copper and 15 or
16 tin. When hammered and tempered duly it is fit for making edge
tools not inferior to some kinds of steel. It is a compound of greater
density than the preceding, though containing more tin; the grain
is fine and the metal free from blisters and suited for turning in
the lathe. It seems to be the best alloy of the kind for printers’
cylinders; but an analysis which I lately made of some turnings from
one of these cylinders gave me much less tin than the above proportion.
The alloy (_b_) is constituted of 6 atoms of copper and 1 of tin.
(_c_). _Alloy for the Chinese gong, cymbals, &c._ An alloy formed of
100 parts copper and 23 tin, appears from Dussaussoy’s experiments to
form the compound of minimum density. It is used for making cymbals;
and nearly accords with the composition of the Chinese gong. It is
formed of 4 atoms of copper and 1 of tin. The Chinese gong analysed by
Klaproth was composed of 100 copper and 28.2 tin; that by Dr. Thomson
of 100 copper and 23.4 tin.
(_d_). _Common bell-metal used for casting bells._ This alloy is
commonly made of 3 parts copper and 1 of tin; but to be in due
proportion for 3 atoms of copper and 1 of tin, it should be formed of
100 copper and 31 tin. It is hard, of a white colour, less malleable
than the preceding alloys, and more sonorous. A specimen I analysed
consisted of 100 copper and 36 tin. The exact proportion of 100 copper
and 31 tin is not essential to produce a sonorous alloy.
(_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.[21]
[Footnote 21: This author obtained the Royal Society’s gold medal for
his essay on the composition, &c. of specula for telescopes. Philos.
Transact. 1787.]
(_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;[22] or 4 parts copper and 1 of zinc by weight nearly.
[Footnote 22: An. of Philos. Vol. 12.]
(_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[23], 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.
[Footnote 23: An. de Chim. & Physique. 5--233.]
(_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[24] |
+----------------+------------------+--------------------+
[Footnote 24: The result for this last article must be considered more
uncertain than any of the previous ones, the experiment being more
complicated.]
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.[25] |
+---------------------+-----------------+-------------------------+
| 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 |
+---------------------+-----------------+-------------------------+
[Footnote 25: That is, the temperature that would be denoted by mercury
inclosed in a vessel having no expansion by heat; or else in one that
expanded in the same rate as mercury.]
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.[26]
[Footnote 26: By recent experiments I find the heat evolved in the
union of oxygen and hydrogen, would raise the temperature of the same
weight of water 6500°.]
“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.