Synthetic Inorganic Chemistry

(^42) QUANTITATIVE ASPECTS OF CHEMISTRY
when the pressure is constant and T stands for the absolute
temperature; when the volume is held constant the pressure
must vary as the absolute temperature, or
Pi=Ti
T
The equations for the laws of Boyle and Charles can be com-
bined into one equation for use when pressure, volume, and tem-
perature vary.
or
P1V1
Piston. J^
S3 Reservoiri - Water
(^111) *" GaugePressure
Dalton's law describes the behavior of mixtures of gases as
follows: When two or more gases are contained in the same vessel
each one exerts the same pressure as if it occupied the whole vessel
alone at that temperature. The
actual measured pressure is the
sum of the partial pressures of
the gases present.
Since we frequently have to
measure gases which are con-
fined over water in the measur-
ing vessel, and are consequently
mixed with water vapor, we are
especially interested in applying
cylinder-^ Dalton's law to water vapor.
A gas may be mixed with any
amount of water vapor up to the
saturation point, and the satura-
tion point depends solely on the
At Pump temperature. We need only to
be sure that the gas is saturated
with water vapor in order to cal-
culate the effect of the latter.
FIG. 14 Saturated Water Vapor. In
order to help us make clear the
properties of saturated water vapor, let us make use of the some-
what idealized apparatus shown in Fig. 14,
I