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0-147*9
0-19145


1620-5
1188-9


239-18
237-63


Mean "'- -


-


-


233-40


Chlorides volatile, R 2 C1 6 .
Chlorate of arsenic ....
,, of phosphorus ...


0-17604
0-20922


2267-8
1720-1


399-26
359-86


Mean. -




-


379-51


Bromates, R^Br".
Bromate of potassium -
of silver -


0-11322
0-07391


1468-2
2330-0


166-21
173-31


Mean ....
Bromate of sodium ....


0-13842


" 1269-2 "


169-76
175-63


Bromates, RBr ! .
Bromate of lead ....


0-05326


2272-8


121-00



CALOR1METRY.



Gl



Names of Substances.


Specific Heats.


\toraic Weights.
(Oxygen =- 100.)


Products.


lodates, R2R
lodate of potassium ....
of sodium -
Prot-iodate of mercury -
of silver - - - -
of copper - ...

Mean -


0-08191
0-08684
0-03949
0-06159
0-06869


2f68-2

I8<>9-2
4100-3
2929-9
2369-7


169-38
1 -2-30
162-34
180-45


167-45


lodates, RP.
lodate of lead -
of mercury -

Mean -


0-04267
0-04197


2872-8
2844-1


122-54
119-36


120-95


Ftuorates, RFR
Fluorate of calcium - - - -


0-21492


489-8


105-31


Nitrates, Az-O 5 +R-O.
Nitrate of potash - - - -
of soda -
of silver -

Mean ....


0-23875
C-27821
0-14352


1266-9
1067-9
2128-6


302-49
97-13
305-S5


301-72


Nitrates, Az 2 O 5 +RO.
Nitrate of barytes -


0-15228


1633-9


248-83


Chlorates, C1 2 O 5 + R 2 O.
Chlorate of potash -


0-20956


1532-4


321-04


Phosphates, P2Q'+2R 2 O (Pyrophosphates).
Phosphate of potash - ...
of soda -

Mean ....


0-19102
0-22833


2072-1
1674-1


395-70
382-22


389-01


Phosphate, FK)5+2 RO.
Phosphate of lead -


0-08208


3681-3


302-14


Phosphate, P-O^-fRO.
Phosphate of lime -


0-19923


1248-3


248-64


Phosphate, P2Q s +3 RO.
Phosphate of lead ....


0-07982


4985-8


397-96


Arsenites, AsO 3 +R"O.
Arsenite of potash ....


0-15631








Arsenites of lead, As-O'+3 PbO.
Arsenite of lead ....


0-07280


56235


409-37


Sulphates, SO 3 +R*O.
Sulphate of potash -
of soda - - - -

Mean -


0-19010
0-23115


1091-1
8921


207-40
206-21


206-80


Sulphates, SO 3 +RO.
Sulphate of barytes -
of strontium ...
oflead -
of lime - - - -
of magnesia -

Mean ....


0-11285
0-14279
008723
0-19656
0-22159


1458-1
1148-5
1895-7
857-2
759-5


164-54
164-01
165-39
16840
168-30


166-15


Chromates.

Chrom ate of potash -
Bi-chromate of potash -


0-18505
18937


12417

18935


229-83
358-67


Borate of potash - - ~


0-21975


1461-9


321-27



HEAT.



Names of Substances.


Specific Heats.


Uomic Weights.
(Oxy K en=100.)


Products.


Borate of soda ....


0-23323


1262-9


30 0-88


Mean -


- . -


-


Jaii-of "


Borates,WO+RO.
Borate of lead -


0-11409


2266-5


258-60


Borafes, B 2 O<:+2 R 2 O.
Borate of potash ....
of soda -


0-20478
0-25709


1025-9
826-9


219-52
212-60


Mean






216-06


Borales, BO 6 +2 RO.
Borate oflead


0-09046


1830-5


164-54


Tungstates.
Wolfram - -


0-09780


M





Silicates.
Zirconia


0-14548


,,





Carbonates, CO2+R2Q.
Carbonate of potash -
ofsoda ....


0-21623
0-27275


865-0
666-0


187-04
181-65


Mean -


-


-


181-35


Carbonates, CQ2+RO.
Carbonate of lime (Iceland spar) -
(Arragonite) -
Marble, white


0-20858
0'208f)0
0-21585
0-209^9


631-0
631-0
631-0
631-0


131-61
131-56
136-20
132-45


Chalk, white
Carbonate of barytes ....
of strontium ...
of iron ....


0-2 '585
11038
014483
0-19345


631-0
1231-9
9223
714-2


185-87

13519
133 58
138 16


Mean -

Carbonate of lead -


~ 0-08596 "
0-21743


" 1669-5 "
582-2


134-40
14355
126-59



Specific Heats of different Bodies determined by M. Rcgnault.



Names.








Srecific Heat*.


Densities.










0" 26085




Charcoal -








024150




Coke of cannel coal








0-20307




of small coal








0-20085




Welsh anthracite coal








0-20171




Phila.lelphian








0-20100




Graphite, natural








0-20187




of smelting furnaces








0-19702




of gas retorts -
Diamond -








0-20360
0-14687




Turpentine








0-4672




Camphildne








0-4656




TerJbilSne








0-45^0




Terebene -








4518




Lemon juice
Orange juice








0-4879
0-J8S6




Gin ...








0-4770




Petroleum - -








0-46R4
O'l 165


7"8f09


tempered








0-1175


7-7982


Metal of acute cymbals -








0-0858


8-57!i7


of soft cymbals, tempered








00862


8-6343


' ' annealed -


-




-


0-1937





LIQUEFACTION AND SOLIDIFICATION.



Names.


Specific Heats.


Densities.


Sulphur naturally crystallized




.


0-1776




melted for two years
,, for two months




-


0-1764
0-1803




recently -






0-1844




Water










Spii it of turpentine
Solution of chlorate of calcium




-


0-4160
0-6448




Spirit of wine, common at 36




_


0-6588




of higher degree
of still higher




-


0-8413
0-9402




Acetic acid concentrated, not crystallized


06501





Specific Heats determined by M. Eegnault.







Specific Heats.






From*0 o 15.


From 15 to 10.


From 10 to 5.


Distilled water








Spirit of turpentine -
Solution of chlorate of calcium


0-6462


0-6389


0-6423


Spirit of wine, common, No. 1.


0-6725


0-6651


0-6588


weaker, No. 2.


0-8518


08429


0-8523


still weaker, No. 3. -


0-9752


0-9682


0-9770


common


0-6774


0-6S40


0-6465


Acetic acid


0-6589


06577


0-1.609


Mercury


o-o-.-to


0-0283


0-0282


Terebene -


0-4267


0-4156


0-4154


Lemon juice - -


0-45 1


0-4424


0-4489


Petroleum -


0-4342


04325


0-4321


Benzine -


0-3932


0-3865


0-3999


Nitrobenzine -


0-3499


03478


03524


Chlorate of silicium -


0-1904


1904


1914


of titanium -


0-1828


0-1802


0-1810


Chloride of tin


01416


0-1402


0-1421


Prntochlorate of phosphorus


0-1991


0-1987


0-2017


Sulphate of carbon


0-2206


0-2183


0-2179


Ether - -


0-5157


0-5158


05207


sulphydric


04772


0-4653


0-4715


io.lhydric


0-1584


0-1584


1587


Spirit of wine - -


0-6148


0-6017


0-5987


Ether, oxalic -


0-4554


0-4. -i21


0-4629


Spirit of wood -


0-R009


0*5S68


0-5901


Ether, iodhydric
bromhydric


0-1569
0-2153


0-1556
02135


0-1574
0-2164


Chlorate of sulphur -


0-2038


0-2024


02048


Acetic acid, crvsUllizable


0-4618


04590


0-4587



CHAP. VII.

LIQUEFACTION AND SOLIDIFICATION.

1431. Thermal phenomena attending liquefaction. It has
been already explained, that when heat is imparted in sufficient
quantity to a solid body, such body will at a certain point pass
into the liquid state ; and when it is abstracted in sufficient
quantity from a liquid, the liquid at a certain point will pass
into the solid state.



64 HEAT.

1432. Certain thermal phenomena of great interest and im-
portance are developed in the progress of these changes, which
it will now be necessary to explain.

Let us suppose that a mass of ice or snow, at the temperature
of 20, is placed in a vessel and immersed in a bath of quick-
silver, under which spirit-lamps are placed. Let one thermo-
meter be immersed in the ice or snow, and another in the mer-
cury. Let the number and force of the lamps be so regulated,
that the thermometer in the mercury shall indicate the uniform
temperature of 200. The mercury imparting heat to the vessel
containing the ice, will first cause the ice to rise from 20 to
32, which will be indicated by the thermometer immersed in
the ice ; but when that thermometer has risen to 32, it will
become stationary, and the ice will begin to be liquefied. This
process of liquefaction will continue for a considerable time,
during which, the thermometer will continue to stand at 32 ;
at the moment that the last portion of ice is liquefied, it will
again begin to rise. The coincidence of this elevation with
the completion of the liquefaction may be easily observed, be-
cause ice, being lighter bulk for bulk than water, will float on
the surface, and so long as a particle of it remains unmelted it
will be visible.

Now, it is evident that during this process, the mercury
maintained at 200 constantly imparts heat to the ice : yet from
the moment the liquefaction begins until it is completed, no in-
crease of temperature is exhibited by the thermometer immersed
in the ice. If during this process no heat were received by the
ice from the mercury, the lamps would cause the temperature
of the mercury to rise above 200, which may be easily proved
by withdrawing the vessel of ice from the mercurial bath
during the process of liquefaction. The moment it is with-
drawn, the thermometer immersed in the mercury, instead of
remaining fixed at 200, would immediately begin to rise, al-
though the action of the lamps remained the same as before;
from which it is obvious that the heat, which on the removal
of the ice causes the mercury to rise above 200, was before
imparted to the melting ice.

1433. It is evident, therefore, that the heat which is received
by the melting ice during the process of liquefaction is
latent in it, being incapable of affecting the thermometer or the
senses.



LIQUEFACTION AND SOLIDIFICATION. 65

If the hand be plunged in the ice at the moment it begins to
melt, and at the moment that its liquefaction is completed, the
sense of cold will be precisely the same, notwithstanding the
large quantity of heat which must have been imparted to the
ice during the process of liquefaction.

1434. Quantity of heat rendered latent in liquefaction.
The quantity of heat which is absorbed and rendered latent in
the process of liquefaction, can be directly ascertained by the
calorimeter of Laplace and Lavoisier (1409). To ascertain this
in the case of ice, it is only necessary to place a pound of water
at any known temperature in the apparatus, and observe the
weight of ice it will dissolve in falling to any other tempera-
ture. In this way it will be found, that hi falling through 142 0> 65
it will dissolve a pound of ice ; and in general, any proposed
weight of water, in falling through this range of temperature,
will give out as much heat as will dissolve its own weight of
ice.

1435. Hence it is inferred, that when ice is liquefied, it ab-
sorbs and renders latent as much heat as would be sufficient to
raise its own weight of water from 32 to 32+142-65 =
!74-65.

1436. The latent heat of water has for the last half century
been estimated at 135, that having been the result of the ex-
perimental researches of Lavoisier and Laplace. Dr. Black's
estimate was 140, and that of Cavendish 150. A series of ex-
periments have lately been made, under conditions of greater
precision, by MM. de la Provostaye and Desains, from which
the above estimate has been inferred.

Dr. Black, who first noticed this remarkable fact, inferred
that ice is converted into water by communicating to it a
certain dose of heat, which enters into combination with it in a
manner analogous to that which takes place when bodies combine
chemically. The heat thus combined with the ice losing its
property of affecting the senses or the thermometer, the phe-
nomenon bears a resemblance to those cases of chemical combi-
nation, in which the constituent elements change their sensible
properties when they form the compound.

1437. Latent heat rendered sensible by congelation. If it be
true that water is formed by the combination of a large quantity
of heat with ice, it would necessarily follow, that, in the recon-
version of water into ice, or in the process of congelation, a cor-



66 HEAT.

responding quantity of heat must be disengaged. This fact
can be easily established, by reversing the experiment just
described.

Let us suppose that a vessel containing water at 60 is im-
mersed in a bath of mercury at the temperatui-e of 60 below
the freezing point. If one thermometer be immersed in the
mercury, and another in the water, the former will gradually
rise, and the latter fall, until the latter indicates 32. This ther-
mometer will then become stationary, and the water will begin
to freeze; meanwhile the thermometer immersed in the mercury
will still rise, proving that the water while it freezes continually
imparts heat to the mercury, although the thermometer im-
mersed in the freezing water does not fall. When the congela-
tion is completed, and the whole quantity of water is reduced
to the solid state, then, and not until then, the thermometer
immersed in the ice will again begin to fall. The thermometer
immersed in the mercury will rise without interruption, until
the two thermometers meet at some temperature below 32.

1438. It is evident from this, that the heat which was latent
in the water while in the liquid state, is gradually disengaged
in the process of congelation ; and since the temperature of the
ice remains the same as that of the water before congelation, the
heat thus disengaged must pass to some other object, which in
this case is the mercury.

When congelation takes place under ordinary circumstances,
the latent heat which is disengaged from the water which
becomes solid is in the first instance imparted to the water
which remains in the liquid state. When this water passes into
the solid state, the heat which is disengaged from it is transmit-
ted to the adjacent water which remains in the liquid state;
and so on.

1439. Other methods of determining the latent heat of water.
The latent heat of water may be further illustrated experi-
mentally as follows. Let two equal vessels, one containing a
pound of ice at 32, and the>other containing a pound of water
at 32, be both immersed in the same mercurial bath, maintained
by lamps or otherwise at the uniform temperature of 300, and
let thermometers be placed in the ice and the water. The ice
will immediately begin to melt, and the thermometer immersed
in it will remain stationary. The thermometer immersed in the
water will, however, at the same time begin to rise. When the



LIQUEFACTION AND SOLIDIFICATION. 67

liquefaction of the ice has been completed, and the thermometer
immersed in it just begins to rise, the thermometer immersed in
the water will be observed to stand at 174-65. It follows
therefore, supposing the ice and the water to receive the same
quantity of heat from the mercury which surrounds them, that
as much heat is necessary to liquefy a pound of ice as is suffi-
cient to raise a pound of water from 32 to 176 0> 65, which is
142 0- 65; a result which confirms what has been already stated.

1440. The following experiment will further illustrate this
important fact.

First let a pound of ice at 32 be placed in a vessel, and let
a pound of water at 174 '65 be poured into the same vessel.
The hot \vater will gradually dissolve the ice, and the tempe-
rature of the mixture will rapidly fall ; when the ice has been
completely dissolved, the water formed by the mixture will have
the temperature of 32. Thus although the pound of warm
water has lost 142 0> 65, the pound of ice has received no increase
whatever of temperature. It has merely been liquefied, but re-
tains the same temperature as it had in the solid state.

That it is the process of liquefaction alone which prevents the
heat received by the ice when melted from being sensible to the
thermometer, may be proved by the following experiment.

Let a pound of water at 32 be mixed with a pound of water
at 174'65, and the mixture will have the temperature of 103,
exactly intermediate between the temperatures of the compounds.
But if the pound of water at 32 had been solid instead of
liquid, then the mixture would have had, as already explained,
the temperature of 32. It is evident, therefore, that it is the
process of liquefaction, and it alone, which renders latent or in-
sensible all that heat which is sensible when the pound of water
at 32 is liquid.

1441. Liquefaction and congelation must always be gradual
processes. It was formerly supposed that water at 32 would
pass at once from the liquid to the solid state, on losing the
least portion of heat ; and that, on the other hand, a mass of ice
would pass instantly from the solid to the liquid state, on re-
ceiving the least addition of heat. What has been just explained,
however, shows that this sudden transition from the one state to
the other cannot take place.

1442. When a mass of water losing heat gradually is reduced
to 32, small portions of ice are formed, which give out their



68 HEAT.

latent heat to the surrounding liquid, and for the moment
prevent its congelation. As this liquid parts with its heat to
surrounding objects, more ice is formed, which in like manner
disengages its latent heat, and communicates it to a portion of
the water still remaining liquid, thus tending to raise its tem-
perature and keep it in the liquid state. The rapidity of the
congelation will depend on the rate at which the uncongealed
portion of the water can impart its heat to the surrounding air
and other adjacent objects.

The same principles explain the gradual process of the lique-
faction of ice. A small portion of ice first receives heat from
some external source, and having received as much heat as
would raise its own weight of water through 142'6o of the ther-
mometric scale, it becomes liquid. Then an additional portion of
ice receives the same addition of heat, and is likewise rendered
liquid ; and so the process goes on until the whole mass of ice is
liquefied.

1443. Water may continue in the liquid state below 32. It
is possible, under certain circumstances, to maintain water in the
liquid state below the freezing point. If a vessel of water be
carefully covered up, free from agitation, and exposed to a tem-
perature of 22, it will gradually fall to that temperature, still
remaining in the liquid state ; but if it be agitated, or a particle
of ice or other solid body be dropped into it, its temperature
will suddenly rise to 32, and a portion of it will be converted
into ice.

1444. Explanation of this anomaly. To explain this sin-
gular fact, it must be considered that the portion of the liquid
which is thus suddenly solidified disengages its latent heat,
which is communicated to that part of the water which still
remains liquid, and raises it from 22 to 32, and the remainder
of the heat thus disengaged becomes sensible, instead of being
latent in the ice itself, whose temperature it raises from 22
to 32.

It follows, from what has been already explained, that the
entire quantity of latent heat disengaged in this case would be
sufficient to raise as much water as is equal in weight to the
ice which has been formed through 142'6o, or, what is the
same, it would raise 14^ times this quantity of water through
10. Now, in the present case, the whole quantity of water in
the vessel, including the frozen part, has in fact been raised



LIQUEFACTION AND SOLIDIFICATION. 69

10, and it would follow, therefore, that the frozen portion
should constitute one part in 14^ of the whole mass.

This test of the quantity of latent heat of water was applied
with complete success, experimentally, by Dr. Thomson, who
showed, that when water cooled without congelation to 22 was
suddenly agitated, a portion was congealed, which bore the
proportion to the whole quantity just mentioned, that is to say,
10 parts in 142-65 of the entire mass. He found, likewise,
that the same result was obtained when the water was cooled
to any other temperature below 32 without congelation. Thus,
when water cooled to the temperature of 27 without congelation
was agitated, it was found that 28'5 part of the whole mass was
congealed. In this case, the whole mass was raised through 5 ;
and since the heat developed by the frozen portion would be
sufficient to raise 28 times this portion through 5, it follows
that the frozen portion must be the 28 - 5 part of the whole
mass.

1445. Useful effects produced by the heat absorbed in lique-
faction and developed in congelation. The great quantity of
heat absorbed by ice when it melts, and given out by water
when it freezes, subserves to the most important uses in the
economy of nature. It is from this cause that the ocean, seas,
and other large natural collections of water are most powerful
agents in equalizing the temperature of the inhabited parts of
the globe. In the colder regions, every ton of water converted
into ice gives out and diffuses in the surrounding region as
much heat as would raise a ton of liquid water from 32 to
!74-65; and, on the other hand, when a rise of temperature
takes place, the thawing of the ice absorbs a like quantity of
heat : thus, in the one case, supplying heat to the atmosphere
when the temperature falls ; and, in the other, absorbing heat
from it when the temperature rises. Hence we see why the
variations in climate are less on the sea-coast and on islands,
than in the interior of large continents.

The temperature of the air under the line does not vary
much more than 4, and that of the water varies not more
than 1.

1446. Heat absorbed and developed in the liquefaction and
solidification of other bodies. The thermal phenomena ex-
plained above with reference to water belong to a general class,



70 HEAT.

and are common, with certain modifications, to all solids which
are transformed into liquids by the addition, and to all liquids
which are transformed into solids by the abstraction, of heat.
Thus, if a mass of tin have its temperature raised by the addition
of heat until it attain the temperature of 442, it will then
become stationary, notwithstanding it receive further increments
of heat ; but the moment it becomes stationary, its fusion will
begin, and it will continue steadily at the temperature of 442
until it be completed ; but the moment the last particle of tin
has been melted, its temperature will begin to rise.

In the same manner, if lead be submitted to an in 'Tease of
temperature, it will begin to liquefy when it reaches the tem-
perature of 594; and notwithstanding the additional quantities
of heat imparted to it, its temperature will not rise above 594,
until its fusion is completed. In a word, all metals whatever,
and in general all solids which by elevation of temperature
are fused, undergo, during the process of fusion, no elevation
of temperature ; the heat imparted to them during this process
becoming latent in them, since it does not affect the ther-
mometer.

1447. Latent heat of fusion. This heat is called the latent
heat of fusion, and its quantity for each body is determined by
means similar to those already explained for water.

1448. Points of fusion. Different solids are fused at different
temperatures, but the same solid is always fused at the same
temperature, which temperature is called its point of fusion.
This point of fusion constitutes, therefore, a specific character
of the solid. The quantity of heat rendered latent during the
fusion of different metals is different, but always the same for
the same metal. This quantity is estimated or expressed by
the number of degrees which it would raise the same weight of
the same body, supposing it not to undergo the change from
the solid to the liquid state. In the same manner, all liquids
which, by the loss of heat, are converted into solids, have a
certain point, the same for each liquid, but different for different
liquids, at which they pass into the solid form. This point is
called their point of solidification, or their freezing point. It
is customary to apply the latter term only to such bodies as at
common temperatures are found in the liquid state.

The point at which a body in the liquid state solidifies, is the



LIQUEFACTION AND SOLIDIFICATION.



71



same as that at which the same body in the solid state is liquefied ;
the points, therefore, of solidification or congelation are the
same as the points of fusion or liquefaction for the same bodies.
Thus the point of fusion for ice is the same as the freezing
point for water.

Two conditions are therefore necessary to the fusion of a
solid body : first, its temperature must be reduced to the point
of fusion ; and, secondly, it must receive a certain quantity of
heat, called its heat of fusion, which will become latent in it
when the fusion has been completed.

In like manner two conditions are necessaiy to the congelation
or solidification of a liquid : first, it must be reduced to its freez-



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