DOC.
12
COMMENTS ON
EÖTVÖS'S
LAW
407
[2]See Eötvös 1886.
The
difference
between
t
and the critical
temperature is
about
6°
for
most
substances.
See,
e.g.,
Freundlich
1922, pp.
43-45,
for
more
details. Eötvös's
law
and the
experi-
mental work
bearing
on
it
are
also reviewed in Nernst
1893,
which is
mentioned in Einstein's
Scratch Notebook
(Appendix
A),
[p.
20].
[3]This
assumption,
which
is
sometimes called
Guldberg's
rule,
is
only
valid
if
the critical
pressures
of the
compared
substances
are
not too
different; see,
e.g.,
Kamerlingh
Onnes and
Keesom
1912, p.
932.
[4]See
Nernst
1909,
pp. 277-279,
for
a
discussion of Trouton's
rule
(also
in
connection with
Guldberg's
rule).
[5]Ds
is
the molar heat of
evaporation.
[6]See
also Einstein
1901
(Vol.
2,
Doc.
1),
p. 514,
for Einstein's earlier
use
of the linear
dependence
of
y
on
the
temperature.
See
Freundlich
1922,
pp.
38-40,
for
a
discussion of the
temperature dependence
of the surface tension.
[7]Uf should
be
Uf.
[8]See,
e.g.,
Van
der
Waals
1894,
which contains calculations similar
to
the
ones
that lead
to
the
expression
for
Uf
below. A reference to
this
paper,
which also discusses Eötvös's
law,
appears
in
Einstein's Scratch Notebook
(Appendix
A),
[p.
20].
[9]N
is
Avogadro's
number.
[10]A
factor
of
1\2
is missing
in
the
right-hand
side.
[11]The
expression
for
K2
corrects
a
mistake
in
Einstein
1901
(Vol. 2,
Doc.
1).
See note
1.
[12]In
a
letter
to
Einstein of
1
February 1912,
Richard Swinne
pointed
out
that, in
fact,
there
might
be
no
contradiction between
eqs. (1b)
[or
(1c)]
and
(2)
since
experimental investigations
seemed
to
indicate that
in
(1b)
the factor
y2/3
should
be
replaced
by
vs
(see, e.g.,
Walden
1909).
Swinne also noted
that
experiments
had shown that
yu2/3
was
not
a
linear function of
tempera-
ture
under
all
circumstances
(see, e.g.,
Walden
1911).
[13]Validity of
eq. (2)
implies
that
eqs.
(1),
(1a),
and
(1b) are
linear
in
vs,
and thus
in
M,
the
molecular
weight.
Since
the denominator of
(1b)
is
linear
in
M
as well,
M would
drop
out
of
the
quotient.
[14]In
a
review
of Einstein's
paper,
Sackur remarked
that
this
assumption
is
clearly not
valid for
all fluids
(Sackur 1910,
p.
16).
[15]The
molecular model introduced
here-the
lattice
picture together
with the
assumption
that
only neighboring
molecules
interact-is
applied
to
solids
in
Einstein
1911b
(Doc.
13),
which
immediately
followed the
present paper
in
the
same
issue of
the Annalen
der
Physik.
[16]Georg
Bredig (1868-1944)
was
Professor of Physical Chemistry and Electrochemistry at
the ETH.
[17]n
should
be
1/n
in
the
sentence
beginning,
"Es
ergibt
sich."