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ing point; and, secondly, it must be deprived of a certain
quantity of heat, which exists latent in it, and maintains it in
the liquid state.

In the following table are given the points of fusion of the
several bodies named in the first column.

Table showing the Point of Fusion of various Substances in
Degrees of Fahrenheit's Thermometer.



Nimes of Substances.




Fahr.


Authorities.


Plntina
Knglish wrought iron
French do


-


3082
2912
2732


Clarke.
Pouillet and Vauquelin.


Steel desist fusible) -




2A52




(most fusible)




2372




Cast manganese




22H2




brown, fusible -




2192




very fusible
whito, fusible -




2012

2012


!> Pouillet.


very fusible
Gold, very pure




1922
22x2




money




21- ^6




Copper




1922




Brass .




18.^9


Daniell.


Bronze




1652


1 Pouillet.


Antimony -




810


3




r


700


Murray.


Zinc


]


705


Cfuyton Morveau.




I


6*0


P.millet.




c


608


Pouillet.


Lead


I


590
592


Irvine.
Guy ton Morveau.




r


509


Ermann.


Bismuth ....




505

477


Pouillet.
Irvine.




I




Crichton.




c


512


Cuyton Morveau.


Tin




446
442


Pouillet.
Crichton.




L


433


Ermann.



72



HEAT.



Names of Substances.


Fahr.


Authorities.


Alloy ft parts tin, 1 part lead


381




4 -


372




3 ;; ;; -


367




,, 2 - -


385






466




If 1 3 parts lead
Alloy 3 parts tin, 1 part bismuth -


552
392
333-9


> Pouillet.


1 -


286-2




" 4 " 1 part lead, 5 parts bis-






muth -


246




Sulphur . . . -


237
226


J
Dumas.


Iodine


225


I


Alloy 2 parts lead, 3 parts tin, 5 parts bis-
muth -


212


!> Pouillet.


5 3 i> 8 ,, -


212




,, 1 i, 1 i 4


201


J


Potash . . . . T


194
162


Gay Lussac and Thenard, Pouillet.
Gay Lussac and Thenard.




136


] Pouillet.


Phosphorus i


100


Murray.


Stearicacid


158




Wax, bleached -


154




unbleached -


14-2




r-


131




Margaric acid }


to







140







120




Stearine <


to


Pouillet.




109




Spermaceti -


120




Acetic acid - - - -


113




Tallow ....


92




Ice


32 '




Oil of turpentine -


14




Mercury .....


382





1449. Latent heat of fusion of certain bodies. The latent
heat of fusion has not been so extensively investigated.
M. Person has, however, determined it for the bodies named in
the following table. The points of fusion observed by M. Person,
for the specimens tried, are given. The unit of the numbers
expressing the latent heat is, in this case, the quantity of heat
necessary to raise the same weight of water from 32 to 33.



Names of Substances.


Points
of
Fu.ion.


Latent Heat
for t'nitv
of Weight.


Names of Substances.


Points
of
Fusion.


Latent Heat!
ofWeight.


Chloride of lime
Phosphate of soda
Phosphorus -
Bees-wax (yellow)
D'Arcet s alloy
Sulphur


83-3
97-5
111-6
143-6

204-8
239-0


82-42
98-37
8-48
7832
1073
16-51


Tin -
Bismuth
Nitrate of soda
Lead -
Nitrate of potash
Zinc - -


455-0
518-0
f>90-9
629-6
642-2
793-4


25-74
22-32
1 13-36
9-27
83-12
49-43



1450. Facility of liquefaction proportional to the quantity of
latent heat. The different quantities of latent heat peculiar
to different bodies, explain the different degrees of facility with



LIQUEFACTION AXD SOLIDIFICATION. 73

which they are liquefied. Ice liquefies very slowly, because its
latent heat is considerable. Phosphorus and lead, on the other
hand, whose latent heat is small, melt very rapidly. Ice cannot
be liquefied until it lias received as much heat as would raise its
own weight of water 142-65; while lead and phosphorus are
liquefied by as much heat as would raise their own weight of
water 9. Hence it will be understood why it is that glaciers
and vast depths of snow continue on mountain ridges, such as
the Alps, in spite of the heat imparted to them during the
hottest summers ; such heat, however considerable, being only
sufficient to liquefy a portion of their superficial strata, which
descends the declivities, and feeds the streams and rivers of
which they are the sources.

1451. Other bodies besides ivater may continue liquid below
the point of solidification. The circumstance of water con-
tinuing in the liquid state below its freezing point, when kept
free from agitation, is not peculiar to that liquid. Tin fused in
a crucible was cooled by Mr. Crichton 4 below its melting
point, and yet remained liquid ; and similar phenomena have
been observed with other metals. In all such cases, the moment
solidification commences, the liquid, as in the case of water,
suddenly rises to its point of fusion ; and the same causes in all
cases favour solidification.

1452. Refractory bodies. Bodies which are difficult of
fusion are called refractory bodies. Among these, one of the
most remarkable is carbon or charcoal, one form of which is the
precious stone called the diamond. No degree of heat, as yet
attained, has reduced this substance to the liquid state ; indeed,
diamond being crystallized charcoal, it is probable that if the
fusion of charcoal could be effected, diamonds could be fabricated.
Among the most refractory bodies are the earths, such as lime,
alumina, barytes, strontia, &c. Of the metals, the most refractory
are iron and platinum, but both of these are fused by the oxy-
hydrogen blowpipe, as well as by the galvanic current.

1453. Alloys liquefy more easily than their constituents. It
is found that alloys composed of the mixture of two or more
metals, in certain proportions, frequently liquefy at a much
lower temperature than either of their constituents. Thus a
solder composed of 4 parts of lead and 6 of tin fuses at 336.
An alloy composed of 8 parts of bismuth, 5 of lead, and 3 of tin,
liquefies at a temperature below that of boiling water ; and an

II. E



74 HEAT.

alloy composed of 496 bismuth, 310 lead, 177 tin, and 26
mercury, fuses at 162-5. If a thin strip of this alloy be dipped
into water that is nearly boiling hot, it will melt like wax.

1454. Some bodies infusing pass throuyh different degrees of
fluidity. Some bodies, like water, pass from the complete solid

to the complete liquid state without passing through any in-
termediate degrees of aggregation ; while others, like wax,
tallow, and butter, become soft at temperatures considerably
below those at which they are liquefied ; and there are others,
like glass and some of the metals, which never, at any tem-
perature, attain absolute fluidity.

1455. Singular effects manifested by sulphur. Sulphur also
presents some curious exceptional circumstances in its state of
aggregation at different temperatures. If heat be gradually and
slowly imparted to it, it will be fused, and become very fluid at
302. If the supply of heat be continued, it will change its
colour and become red and viscous and considerably less fluid.
At length, heat being further supplied, and its temperature being
raised from 430 to 480, it will become altogether red, opaque,
and acquire the consistency of a thick paste.

1456. Points of congelation lowered by the solution of foreign
matter. The freezing points of liquids are generally lowered
when solids are dissolved in them. Thus, when salt is dis-
solved in water, the freezing point of the solution is always
below 32, and its distance below it depends on the quality and
quantity of salt in solution.

1457. Points of congelation of acid solutions. The strong ]
acids generally freeze at much lower temperatures than water ; j
and if they be mixed with water, the freezing point of the
mixture will hold an intermediate position between those of j
water and the pure acid. The freezing points of the acids them- ]
selves vary with their strength, but not according to any known 1
or regular law.

1458. Sudden change of volume accompanies congelation. j
When a liquid passes into the solid state by the absorption of \
heat, a sudden and considerable change of dimensions is fre- J
quently observed. This change is sometimes an increase and 1
sometimes a diminution, and in some cases no change takes
place at all. When mercury is cooled to its freezing point,
which is 39, it undergoes an instantaneous and considerable
diminution of bulk as it passes into the solid state. An
effect exactly the reverse takes place with water. When this



LIQUEFACTION AND SOLIDIFICATION. 75

liquid cools down to 32, it passes into the solid state, and in
doing so undergoes a considerable and irresistible expansion.
So great is this expansion, and so powerful is the force with
which it takes place, that large rocks are frequently burst when
water collected in their crevices freezes. It is a common oc-
currence that glass bottles containing water, left in dressing-
rooms in cold weather, in the absence of fire are broken when
the water contained in them freezes, the expansion in freezing
not being yielded to by any corresponding dilatation in the glass.
An experiment was made at Florence on a brass globe of con-
siderable strength, which was filled with water, and closed by a
screw. The water was frozen within the globe, by exposure
to a cold below 32, and in the process of freezing the water
burst the globe. It was calculated that the force necessary to
produce this effect amounted to about 28,000 Ibs.

1459. This expansion in the case of water not identical with
that which takes place below the point of greatest density.
This sudden expansion of water in freezing is a phenomenon
distinct from the expansion already noticed, which takes place
as the temperature is lowered from 38-8 to 32. The latter ex-
pansion is gradual and regular, and accompained by a gradual
and regular decrease of temperature ; but, on the other hand,
the expansion which takes place when water passes from the
state of liquid to the state of ice is sudden and even instantaneous,
and is accompanied by no change of temperature, the solid ice
having the temperature of 32, and the liquid of which it isformed
having had the same temperature just before congelation.

1460. The quantity of expansion produced in congelation is
the same for the same liquid, at ivhaterer temperature conge-
lation takes place. When water is cooled below 32 without
freezing, the expansion which took place from 38 0- 8 to 32 is
continued, and the liquid continues to dilate below 32 : when it
is afterwards solidified by agitation, or by throwing in a crystal
of ice, a sudden and considerable expansion takes place
as already described, but this expansion is always less than
would take place if it solidified at 32, by the quantity of. ex-
pansion which it suffered in cooling from 32 to the temperature
at which it was solidified. It is observed, that the expansion
which water suffers in being solidified at 32 amounts to about
one-seventh of its bulk. If it be solidified at a lower tempera-
ture, it will suffer a less expansion than this ; but the expansion



76 HEAT.

which it suffers in solidification under these circumstances, added
to the expansion which it suffers in cooling from 32 down-
wards previous to solidification, will always produce a total
amount equal to the expansion w r hich it would suffer in solidi-
fying at 32. Hence the total expansion which water under-
goes, from the temperature of greatest density (38'8) until it
becomes solid, is always the same, whatever be the temperature
at which it passes from the liquid to the solid state. The same
observations will be likewise applicable to other liquids similarly
solidified.

1461. Phosphorus and oils in general contract in congealing.

If a quantity of liquid phosphorus, at the temperature of
200, be gradually cooled, it will be observed to suffer a regular
contraction in its dimensions, according to the general laws
observed in the cooling of bodies. When it is cooled to the
temperature of about 100, it passes into the solid state, and in
doing so undergoes a sudden and considerable contraction.
Oils generally undergo this sudden contraction in the process
of freezing.

1462. Some bodies expand, and some contract, in congelation.

It may be assumed as generally true, that bodies which
crystallise in freezing undergo a sudden expansion, and that
bodies that do not crystallize in freezing, for the most part
suffer a sudden contraction. Sulphuric acid, however, is an ex-
ample of a liquid which passes from the liquid to the solid state,
and vice versa, without any discoverable expansion or contrac-
tion. Most of the metals contract in passing from the liquid
to the solid state, the exceptions being cast iron, bismuth, and
antimony, all of which undergo expansion in solidifying.

1463. Why coin is stamped, and not cast. It is evident that
a metal which contracts in solidifying cannot be made to take
the exact shape of the mould. It is for this reason that money
composed of silver, gold, or copper cannot be cast, but must be
stamped. Cast iron, on the contrary, as it dilates in solidifying,
takes the impression of a mould with great precision, as do also
certain alloys used in the arts.

1464. Contraction of mercury in cooling. The most strik- J
ing instance of sudden contraction in cooling is exhibited in the
case of mercury. This was first observed in the case of a ther- ?
mometer, which when exposed to a temperature about 40 below
zero, was observed to fall suddenly through a considerable range



LIQUEFACTION AXD SOLIDIFICATION. 77

of the scale, and in some cases the mercury was precipitated
into the bulb. It was observed that the thermometer being
exposed to a temperature lower than 40, the mercury gra-
dually falls until it arrives at about 38, and that then a great
and sudden contraction takes place at the moment the metal is
solidified.

This contraction, however, must not be understood as indi-
cating any real fall of temperature, as is the case with all the
previous and regular contractions which take place before the
solidification of the metal.

1465. Substances which soften before fusion. Substances
which soften before they melt, and which pass by degrees
from the solid to the liquid state, are mostly of organic origin,
and their point of fusion is below the temperature of boiling
water. Some of these, which are of most general utility in the
arts, are the following :

Colophany begins to melt at 275
Brown wax 110

White wax 124

Tallow 104

Pitch 91

1466. Weldable metals. The metals capable of being
welded soften before they are fused ; and the heat at which
they soften is called a welding heat. The metals which most
readily admit of being welded, are platinum and iron. At an
incipient white heat (2372) they become soft ; and, in this
state, pieces of the metal may be intimately united when
submitted to severe pressure, or when passed under the
hammer.

1467. Freezing mixtures. It may be taken as a physical
law of high generality, that a solid cannot pass into the liquid
state without absorbing and rendering latent a certain quantity
of heat. This heat may be, and often is supplied from some
other body in contact with that which is liquefied. But if no
such external supply of heat be present, and if, nevertheless, any
physical agency cause the liquefaction to take place, the body
thus liquefied will actually absorb its own sensible heat. While
it is liquefied, it will therefore fall in temperature to that extent
which is necessary to supply its latent heat of fluidity at the
expense of its sensible heat.

To render this more clear, let us imagine a pound of ice at



78 HEAT.

the temperature of 32 to be mixed with a pound of liquid
having the temperature of 103, and let this liquid be sup-
posed to have the property of dissolving the ice. When the
liquefaction is completed, the temperature of the mixture will
be 103. Now the liquid, which is here supposed to be the
solvent, neither imparts heat to the ice nor abstracts heat from
it. The ice therefore, now liquefied, contains exactly as much
heat as it contained before liquefaction, and no more. But, to
become liquid, it was necessary that 142'6o of heat should be
absorbed by it, and become latent in it. This 142 0< 65 has there-
fore been transferred from the sensible to the latent state in.
the ice itself.

This principle has been applied extensively in scientific
researches and in the arts for the production of artificial cold,
the compounds thus made being called freezing mixtures.

In all freezing mixtures, two or more substances are com-
bined, one or more of which are solid, and which have chemical
properties in virtue of which, when intimately mixed to-
gether, they enter into combination, and, in combining, liquefy.
The operation is so conducted, that no heat is supplied either by
the vessel in which the liquefaction takes place, or from any
other external source. Such being the case, it follows that
the heat absorbed in the liquefaction must be supplied by the
substances themselves which compose the mixture, and which
must therefore suffer a depression of temperature proportional
to the quantity of heat thus rendered latent.

The cold produced will be increased by reducing the tempe-
rature of the substances composing the mixture before mixing
them. Thus, let A and B be the substances mixed. Before
being combined, let them be reduced to 32 by immersing them
in snow. Let them then be mixed, and let the latent heat of
fusion be 32. The mixture will fall to zero, since the 32 3 of
sensible heat will be absorbed. But if, at the moment of mixing
them, their temperature had been 64, then the temperature of
the mixture would become 32.

The substances which may be used to produce freezing
mixtures on this principle are very various.

If equal weights of snow and common salt at 32 be mixed,
they will liquefy, and the temperature will fall to 9.

If 2 Ibs. of muriate of lime and 1 Ib. of snow be separately re-
duced to 9 in this liquid and then mixed, they will liquefy,
and the temperature will fall to 74.



LIQUEFACTION AND SOLIDIFICATION. 79

If 4 Ibs. of snow and 5 Ibs. of sulphuric acid be reduced to
74 in this last mixture, and then mixed, they will liquefy,,
and the temperature will fall to 90.

If a pound of snow be dissolved in about two quarts of
alcohol at 32, the mixture will fall nearly to 13. If
the same quantities of snow and alcohol, being reduced in
this mixture to 13, be then mixed, the temperature of the
mixture will be reduced to 58; and the same process being
repeated with like quantities in this second mixture, a further
reduction of temperature to 98 may be produced ; and so on.

1468. Apparatus for producing artificial cold. Freezing
mixtures are used for the artificial production of ice in hot
climates. The most simple apparatus for this purpose is repre-
sented \r\jig. 440., and is composed of a tin bucket B, having a
slightly conical form, in the bottom of which is a circular hole,
a little less in diameter than the bottom. In this hole is sol-
dered the mouth of another tin bucket, G E F H, also conical, but
with its smaller end upwards. A space w is thus left between





Fig. 441.

the two tin buckets, in which the water or other substance to
be cooled is placed.

The freezing mixture is placed in another vessel, IKLM,
jig. 441., similar in form to the bucket ABCD. This vessel
IKLM ought to be made of some non-conducting material.

E 4



80



HEAT.



Common glazed earthenware would answer the purpose.
When the freezing mixture is placed in it, the vessel A B c i> is
immersed in it, as represented in Jig. 440. ; so that the cold
liquid is not only in contact with the external surface of the tin
bucket AB c D, but also with the inner surface of G E F H. The
water w, or whatever other substance it is required to cool, is
therefore quickly reduced in temperature.

If it be not convenient to provide a vessel sucli as i K L M in
earthenware, a tin vessel thickly coated with woollen cloth may
be used.

1469. Table of freezing mixtures. There are a great
variety of bodies which, by combination, serve for freezing
mixtures. The following table has been collected from the
results of the researches of Walker and Lowitz. The substances
are indicated by letters as follows :



Water -
Snow, or ice
Sulphate of ammonia

,, soda

Muriate of ammonia

soda
lime
Carbonate of soda



W

I

SA
SS
MA
MS
ML
CS



Nitrate of potash

ammonia
Sulphuric acid
Nitric acid
Hydrochloric acid
Dilute -
Crystallized



- NP

NA
SA
NA

HA

d



The figures prefixed indicate the proportion by weight in
which the ingredients are mixed. Thus, 6ss + 4>iA -f- 2NP + 4dNA
signifies a mixture of 6 oz. of sulphate of soda, 4 oz. of muriate
of ammonia, 2 oz. of nitrate of potash, and 4 oz. of dilute nitric
acid.









Cold








Cold




From


to


dSced.




From


to


pro-
duced.


I5MA+5 NP+16W


+50


+ 10


40


I2I45MS+5NA


X


25




5 MA+5 NP+8 SS+








3I+2dSA


+32


23


55


16 W -


+50


+4


46


8 1+5 HA - -


+32


27


59


1 NA+1 W - -


+50


+4


4G


7 1+4 dNA


+32


30


62


1 NA+1 CS+1 W -


+ 50


7


57


4 1+5 ML -


+3-2


40


72


3 SS+2 dNA - -


+ 50


3


53


2 1+3 cML - -




50


82


6 SS+4 MA+2 NP+








3 1+4 NP -


+3i


-51




+4 dNA -


+50


-10


60


5 PS+3 NA+4 dNA





31


34


6SS+5 NA+4dNA


+50


-14


64


3I+i!dNA





46


46


9 PS+4 dNA - -


?50


12


62


8 1+3 dSA+3dNA -


10


56


46


9 PS+G NA+4 dNA


+50


21


71


11+ldSA - -


20


-60


40


8 SS+5 HA


+50





50


3 1+4 ML -


+20


-48




5 SS+4 dSA


+50


+3


47


2 1+3 ML -


15


68


53


2 1 + 1 MS -


X


5




1 !+> cML - -





66


66


51+2MS+1MA -


X


12




1 1+3 cML - -


-40


73


33


24 1+10 MS+5 MA+








8I+10dSA


68


91


23


5NP -


X


18












1470. Extraordinary degrees of artificial cold produced by


Thirolier and Mitehel. Thirolier produced a powerful freezing



LIQUEFACTION AND SOLIDIFICATION. 81

mixture, by solidifying carbonic acid, and mixing it with sul-
phuric acid or sulphuric ether. A temperature 120 below zero,
and therefore 152 below the freezing point, was thus produced.
Mi toh el, repeating the experiment, produced a still more in-
tense cold. He exposed alcohol of the specific gravity of 0'798
successively to the temperatures of 130 and 146. He
states that at the former temperature it had the consistency of
oil, and at the latter resembled melting wax.

1471. Alcohol probably congeals at about 150. If these ex-
periments can be relied on, it may be inferred that the freezing
point of alcohol, so long and hitherto so vainly sought, is pro-
bably about 150, or 182 below the freezing point of water
and 110 below that of mercury.

1472. Precautions necessary in experiments with freezing
mixtures. To ensure success in experiments on extreme
cold produced by freezing mixtures, the salts used must not
have lost their water of crystallization, because in that case they
quickly absorb water, and converting it into ice liberate caloric
and obstruct the cooling. The salts and ice used should be pul-
verized so as to dissolve quickly. When extreme cold is re-
quired, the vessel containing the freezing mixture should be
immersed in another vessel, containing also a freezing mixture,
so as to retard the mixture under experiment from receiving
heat from the vessel which contains it, and a sufficient quantity
of the ingredients forming the freezing mixture should be used.

1473. Greatest natural cold yet observed. The greatest
natural cold of which any record has been kept, was that ob-
served by Professor Hanstean between Krasnqjarsk and Nishne-
Udmiks in 55 N. lat., which he states amounted to 55
(Reaum. ?) = -91-75 F.

At Jakutsk, the mean temperature of December is 44^ F.
In 1828, from January 1 to January 10, the mean tempera-
ture of that place was 58.

In the expedition to China, in December 1839, the Russian
army experienced for several successive days a temperature of
-41-8 F.

1 474. Principle ofjluxes. Examples of their application.
The same principle which explains the effect of freezing mix-
tures, is also applicable to the phenomena attending fluxes in
metallurgy. Fluxes are certain bodies which, when mixed
with others, cause them to fuse at lower temperatures than their



82 HEAT.

proper point of fusion. It is by this means that certain metals
and metallic ores are fused, when exposed to the operation of



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