DOC.
55
FEBRUARY
1915 67
55.
To Michael Polányi
[Berlin,]
10 February 1915
Dear
Colleague,
We
are now
just
dealing
with the
case
that
absolute
zero
is
attainable
through
finite
repetitions
of
your
process,[1]
We
would
like
to arrive at
A.
Well,
you
say:
Now
we
enlarge
V
more
adiabati-
cally
until
we
have arrived at B.
Af-
ter this,
isothermally
until
C,
then
adiabatically
to
B, etc.
The conclu-
sion
thus
is
that the
isotherm B
C
corresponds
no more
to
an
entropy
difference
than the adiabat
C B
does,
q.e.d.
CAB
This
proof applies
in
the
case
that the adiabats
A
B
or
C B
actually
exist.
E.g.,
in
the
case
of
a
change
in volume
of
a
solid
body,
it
is
difficult
to
doubt
the
existence
of
that
zero-adiabat. But whether such kinds of
adiabats
always
exist
is
very questionable.
Then
the
petitio
principii
lies
in the
assumption
of
the
existence of
the
zero-adiabat. There
are cases
in which
this
existence
(in
principle)
is
highly improbable.
Think
of
a
fixed
solution,
in which
the
[...][2]
An adiabatic
re-
versible
change
in
volume of solution
V
at
absolute
zero
obvi-
ously
does
not
exist
here in principle.[3]
Volume
=
V
semipermeable membrane
Solution
Pure
solvent
Solvent
This
is
suspicious,
anyway,
in all
cases
where
the adiabats
touch
the
(T
=
0)-
axis
at
angles
other than
0
[degrees].
With
greetings
from
your
colleague
A.
Einstein.
I wish
you
luck
in
performing your military
service.