DOC.
639
OCTOBER
1918 681
Temperature throughout
15-15.5.
The
specif.
wt.
of
anhydrous
CuCl2
is
indicated
as 3.05;
the
sp. w.,
derived from
CuCl2
+
2
H2O
in
the
same way as
for
Na2SO4
from
Na2SO4
+ 10
H2O,
comes
out to be
3.85.- From
the
former
specif.
wt.
figure
follows
a
molecular volume
of:
0.328,
[from
the
latter,
0.286].[11]
But from
the
increase
in
volume for
the
solution
follows
a
mol.
vol.
of
only
0.12-0.23
(an average
of
0.17).
From
the
friction
(K
=
5),
0.35-0.5
(on
average
0.41)
results.
If
the
volume
resulting
from
the
specif.
wt.
is
inserted for v' in
the
formula,
the n's then
become
substantially
smaller
than the
observed
values;
this
is
even
more
the
case
when
the
observed volume differences
are
used.
However,
if
one
makes
the
assumption
that,
in
solution, CuCl2
adds
1 or
2
water
molecules,
resp.,
then
the
n' figures
following
from
the thus
enlarged
volume
correspond very
much
better
with observations.
Depending on
whether
one
proceeds
from
the
specif.
wt.
of
CuCl2
+
2
H2O
(2.4)
or
from
that
of
anhydr.
CuCl2 (3.05),
the
resulting spec.
wt. for
CuCl2
+
H2O
is either
2.87
or
2.67.
The
following
table contains
the
figures
found in this
way,
whereby
n'2.67
incorporates
those volumes
following
from the
assumption
of
a CuCl2
+
H2O
of
spec.
wt.
2.67.
CuCl2
+
H2O CuCl2
+
2
H2O
%
n'2.67
n'2.87
n'H2O
n'obs.
2 51.1
51.0
51.7
51.0
4
53.3 53.1 54.4 52.7
6
55.6
55.2 57.3 55.0
10
60.3
59.8 63.2 59.6
14 65.5 64.5 69.6
64.7
16 68.1 67.1 73.0 68.5
20 74.0 72.5 79.9 75.0
30
90.7 88.2 100.9 97.3
40 109.3 105.8 124.5
151.0
For
2-20%
the
observed fric-
tion
is
in
very
tolerable
agree-
ment
with
the
calculation
fol-
lowing
from the
assumption
of the addition
of
1 H2O
molecule;
at
30%
the
observed
n'
lies closer to
the
figure
fol-
lowing
from
the addition
of
2
H2O
molecules.
n'
at
40%
is
completely
out of
place; per-
haps
some
material
remained
undissolved there.
From
the
specif.
wt.
of
CuCl2
+
H2O,
0.37 and
0.35
result, resp.,
as
the
mol.
vol.,
which
agrees very
well
with
0.40
following
from
n'
for
the
2-20%
solutions;
although
the
mol.
vol.
of
CuCl2
+
2
H2O
agrees
with
it
even
better:
0.41.
g CuCl2
Water
Solution
Vol.
n'obs.
2
98
ca.
98
51
4 96
ca.
96.5 52.7
6 94
ca.
95 55.0
10 90
ca.
91.5 59.6
14 86
ca.
88.25
64.7
16 84
ca.
86.75 68.5
20 80
ca.
83.75 75.0
30 70
ca.
75 97.3
40 60
ca.
69 151.0