394 - C H E M I 
are produced. The interior fpace or vacancy, is formed 
by an iron grating upon the fupports of the fame metal j 
here it is that the bodies fubjefled to experiments are to 
be placed. The top of this cavity is clofed by means of a 
cover: the middle fpace next to this is deiigned to con¬ 
tain the ice which furrounds the interior compartment: 
this ice is fupported and retained by a grate upon which 
a cloth is fpread ; in proportion as the ice melts, water 
flows through the grate and the cloth, and is collected 
in a veffel placed underneath. Laftly the external place 
or compartment of the apparatus contains ice, intended 
to prevent tl\e effeft of the external heat of the atmofphere. 
To ufe this machine, the middle or fecond fpace is filled 
with pounded ice, as is alfo the cover of the internal 
fphere: the fame thing is done with regard to the exter¬ 
nal fpace, as well as to the general cover of the whole 
machine: the interior,ice is fuffered to drain; and when 
it ceafes to afford water, the covering of the internal 
fpace is raifed to introduce the body, upon which the 
experiment is intended to be made: the covering is to be 
put on immediately, and the whole apparatus remains 
untouched until the included body has acquired the 
temperature of 32°, or the freezing temperature of water, 
which is the common temperature of the internal capa¬ 
city: the quantity of melted water afforded by the melt¬ 
ing ice is then weighed; and this may be conlidered as an 
accurate mealure of the caloric or matter of heat difen- 
gaged from the body, becaufe the fufion of the ice is the 
effefl of this heat only. Experiments of this kind lalt 
fifteen, eighteen, or twenty, hours. 
It is of great confequence, that in this machine there 
fliould be no communication between the middle, or fe¬ 
cond, and the external fpace. The air of the room fhould 
not be lower than 32, becaufe the ice would then receive 
a degree of cold lower than that temperature. 
It is extremely eafy, with this apparatus, to determine 
the phenomena which occur in operations where caloric 
is either difengaged or abforbed. If we vvifh, for in fiance, 
to afcertain the quantity of caloric which is difengaged 
from a folid body in cooling a certain number of de¬ 
grees; let its temperature be firft raifed to 212 0 , it is 
then placed in the interior cavity ffff, fig. 2 and 3, of 
the calorimeter, and allowed to remain till we are certain 
that its temperature is reduced to 32 0 ; the water pro¬ 
duced by melting the ice during its cooling is collected, 
and carefully weighed; and this weight, divided by the 
volume of the body fubmitted to experiment, and mul¬ 
tiplied into the degrees of temperature which it had 
above 32° at the commencement of the experiment, 
gives the proportion of fpecific caloric. 
Fluids are contained in proper veffels, whofe fpecific 
'beat, or caloric,.has been previoufly afcertained, and are 
operated upon in the machine in the fame manner as di¬ 
rected for folids, taking care to dedu£t, from the quan¬ 
tity of water melted during the experiment, the propor¬ 
tion which belongs to the I'pec.ific heat of the containing 
veffel. If the quantity of caloric difengaged during the 
combination of different fubftances is be determined, 
thefe fubftances are to be previoufly reduced to the freez¬ 
ing degree, by keeping them a fufficient time furrounded 
with pounded ice ; the mixture is then to be made in 
•the inner cavity of the calorimeter, in a proper veffel like- 
wife reduced to 32°; and they are kept inclofed till the 
temperature of the combination has returned to the fame 
degree: the quantity of water produced is a meafure of 
the caloric difengaged during the combination. 
To determine the quantity of caloric difengaged dur¬ 
ing combuftion, and during animal refpiration, the com- 
buftible bodies are burnt, or the animals are made to 
breathe, in the interior cavity, and the water produced 
is carefully collected. Guinea-pigs, which have the fa¬ 
culty of very eminently refilling the effects of cold, are 
extremely well adapted for this experiment. 'As the con- 
tiziual renewal of air is abfolutely neceffary in luch ex- 
S T R Y. 
periments, we blow frefli air into the interior cavity of 
the calorimeter, by means of a pipe cleftined for thafc 
purpofe, and allow it to efcape through another pipe of 
the fame kind ; and that the heat of this air may not 
produce errors in the refults of the experiments, the 
tube which conveys it into the machine is made to pafs 
through pounded ice, that it may be reduced to 32 0 be¬ 
fore it arrives at the calorimeter. The air which efcapes 
muft likewife be made to pafs through a tube furrounded 
with ice, included in the interior cavity of the machine, 
and the water which is there produced ninft make a part 
of what is collected, becaufe the caloric difenged from 
this air is part of the product of the experiment. 
It is fomewhat more difficult to determine the fpecific 
caloric contained in the different gaffes, on account of 
their fmail degree of denfity; for, if they are only placed 
in the calorimeter in vefiels like other fluids, the quan¬ 
tity of ice melted is fo fmail, that the refult of the ex¬ 
periment becomes at beft very uncertain. For this fpe- 
cies of experiment, the air muft pals through tv/o metal¬ 
lic worms, or fpiral tubes; one of thefe, through which 
the air paffes, and becomes heated in its way to the ca¬ 
lorimeter, is contained in a veffel full of boiling water ; 
and the other, through which the air circulates within 
the calorimeter to difengage its caloric, is placed in the 
Interior cavity of the machine. By means of a fmail 
thermometer placed at one end of the fecond worm, the 
temperature of the air, as it enters the calorimeter, is de¬ 
termined ; and its temperature in getting out of the in¬ 
terior cavity, is found by another thermometer placed 
at the other end of the worm. By this contrivance we 
are enabled to afcertain the quantity of ice melted by 
determinate quantities of air or gas, while lofing a cer¬ 
tain number of degrees of temperature, and, confequent- 
ly, to determine their feveral degrees of fpecific caloric. 
The fame apparatus, with fome particular precautions, 
may be employed to afcertain the quantity of caloric dif¬ 
engaged by the condenfation of the gafes or vapours of 
different liquids. 
The various experiments which may be made with the 
calorimeter do not afford abfolute conclufions, but only 
give us the meafure of relative quantities; we have there-* 
fore to fix a unit, or ftandard point, from whence to form 
a fcale of the feveral refults. The quantity of caloric 
neceffary to melt a pound of ice has been cholen as this 
unit; and, as it requires a pound of water of the tempe¬ 
rature of 167° to melt a pound of ice, the quantity of 
caloric expreffed by the unit, or ftandard point, is what 
raifes a pound of water from 32 0 to 1^7°. When this 
unit is once determined, we have only to exprefs the 
quantities of caloric difengaged from different bodies, by 
cooling a certain number of degrees, in analogous va¬ 
lues : the following is an eafy mode of calculation, given 
by Lavoilier for this purpole, and applied to one of his 
earlieft experiments. He took 7 lb. 11 oz. 2 gros 36 grs. 
of plate-iron, cut into narrow flips, and rolled up, or ex- 
prefling the quantity in decimals, 77070319 lbs. Thefe 
being heated in a bath of boiling water to about 207-5°, 
were introduced into the interior cavity of the calori¬ 
meter. At the end of eleven hours, when the whole 
quantity of water melted from the ice had thoroughly 
drained off, he found that 1-109795 pounds of ice were 
melted. Hence, the caloric difengaged from the iron by 
cooling 175-5°, having melted 1-109795 pounds of ice, 
how much would have been melted by cooling 135 0 ? 
This queftion gives the following ftatement in direct pro¬ 
portion, 175-5 : 1-109795 : : 135 : ^"0-85384- Dividing 
this quantity by the weight of the whole iron employed, 
viz-. 77070319, the quotient 0-1109 is the quantity of ice 
which would have been melted by one pound of iron 
while cooling through 135° of temperature. 
Fluid fubftances, luch as fulphuric and nitric acids, 
&c. are contained in a matrafs, having a thermometer 
adapted to the cork, with its bulb immerfed in the liquid. 
The 
