82
THE NATURE AND
[■SECT. II.
Body.
Specific gravity
of the gas, air
being unity.
Specific gravity of
liquid, water
being unity.
Temperature.
Force in
atmospheres.
Mechanical power
of equal weights
of the gases.
Carbonic acid gas
1-527
32°
36
Sulphuric acid gas
2-777
1-42
45
■ 2
426
Sulphuretted hydrogen gas
1-192
0-9
50
17
630
Euchlorine gas
2-365
Nitrous oxide
1-527
45
50
Cyanogen
1-818
0-9
45
3-6
395
Ammonia
0-5962
0-76
50
6-5
1057
Muriatic acid gas
1-285
50
40-
Chlorine
2.496
1-33
50
4-
440
Steam of water
0-48
1-000
212
1-
1711
These are the principal researches that have been made on the force of vapours
at different temperatures, when in contact with liquids; but, in order to render
the subject more complete, we must consider the force when not in contact with
the liquids which generate them, and also their density and volume.
Of the Elastic Force of Vapour separated from the Liquids from
which they were generated.
118. It has been remarked, that the elastic force of steam or vapour produced
by increase of temperature ceases to follow the same law where it is not in
contact with the liquid from which it was formed. (Art. 87.) The density of the
steam no longer increases, the force being solely that which prevents it expanding,
and is measured from the quantity it would expand if unconfined. The expansion
by the same increase of temperature having been found to be the same in all
gases and vapours, and the density as the compressing force, as far at least as
60 atmospheres, it becomes an easy task to compute this species of force within
that range of compression.
This will also be further useful in determining the volume occupied by steam
of a given density and temperature as far as about 60 atmospheres: higher we
need not attempt to go for useful purposes; and if we did, our rules would fail, for
there is not even a probable chance of the law, of the density being as the force,
extending to very high degrees of compression.
119. The quantity a gas or vapour expands under a constant pressure, is
found by the following rule.
Rule. To each of the temperatures before and after expansion, add 459. Then
divide the greater sum by the less, and the quotient multiplied by the volume at
the lower temperature will give the volume at the higher temperature.
Or let t be the temperature with the volume v, and t' any other temperature,
then