248 DOC.
9 CRITICAL OPALESCENCE
component
from the second
to
the first container.
This
work
is composed
of the
following
three
parts:
dk
" "
Wp
0^0
(work
of
removal from
the
second
container)
RT
\o
P"
M-
RTa
lg
-
(isothermal
compression
to
the
partial pressure
in
the
first
container)
Po"
dk
" "
+
p
v
M"
(work
of
input
into the
first
container).
The volume of the
liquid
is
neglected
here
compared
with
the
volume
of the
gas.
M"
is
the molecular
weight
of the second
component
in
the
vapor phase.
Since
the
first and
the third
terms cancel out
according
to
Mariotte's
law,
we
get
RT
dty
=
-dk
lgE-it
M"
*p{".o
The function
t|r
can
thus
be
calculated
directly
from the concentrations
and
partial
pressures.
Now
we
have to find
cPtyldv2
for the
state
we
denoted
by
the
index "0."
We
have
lg
n
=
ig
i
+
P
-
Po
//
Po
//
=
lg (1
+
7t)
=
71
-
J
2
• •
where
it
is
the
relative
pressure
change
of the
second
component
with
respect
to
the
original
state.
From the
last two
equations
there
follows
3i|r
_
RT0
di
~
~M"
it
-
it2
1
dv
dk
Differentiating
one more
time with
respect
to
v,
and
considering
that
d_
dv
d_
dk
dv
dk,
we
obtain,
if
we
set
n
=
0 in
the
result,
32i|i
dv2
RT,0
dn
dk
RTo
0
M"
dvs2
dk
M"
1 dp"
y~dk
dv
dk
Taking
this into
account, along
with
the
fact
that