338
DOC.
15
COMMENT ON DOC.
13
Doc.
15
Comment
on My Paper:1
"A
Relationship
between
Elastic Behavior..."
by
A.
Einstein.
[Annalen
der
Physik
34
(1911): 590]
In the
paper
cited above I
mentioned Sutherland
as
the discoverer of the connection
between the
elastic
and
optical
behavior of
solids.
It
escaped
my
notice
that
[3]
E.
Madelung
was
the
first to draw
attention
to this
fundamentally important
connection.2
Madelung
found
a
quantitative relationship
between the
elasticity
and
(optical) proper
frequency
of diatomic
compounds
that
corresponds
exactly
to
the
one
that
I
derived for
monatomic
substances and
that
shows
quite
satisfactory
agreement
with
experience.
It
should be
especially
emphasized
that
Madelung is
able to arrive at his
relation
only by
assuming
that the forces
acting
between the
atoms
of
a
molecule
are
of the
same
order
[4]
of
magnitude as
the
forces
acting
between
like atoms
of
adjacent molecules;
in
other
words,
the molecular bond does
not
seem
to
persist
in
the
solid state
of the
substances
investigated by Madelung;
these
substances
seem
to
be
completely
dissociated. This
[5]
agrees totally
with
the
pictures
to which
the
investigation
of molten
salts has led.
Zurich,
January 1911. (Received
30
January
1911)
[1]
[2]
1
A.
Einstein,
Ann.
d.
Phys.
34
(1911):
170 ff.
2
E.
Madelung,
Nachr.
d.
kgl.
Ges.
d.
Wissensch.
zu Göttingen. Math-phys.
Kl.
(20
Feb. 1909 and
29
Jan.
1910);
Physik.
Zeitschr.
11
(1910):
898-905.