16 DOCUMENT
6
FEBRUARY 1903
and additions. The
first
slip probably
constitutes what
is
presented
here
as
the first three
para-
graphs
of
the document, set
off
by an
asterisk. The other
two slips
constitute what
are
presented
here
as
enclosures
to
the document.
[1]The
preceding
document.
[2]Einstein's
request
that Besso
not pay Maja
Einstein's
salary
is
discussed
in
the
preceding
document.
[3]Bernardo
Ansbacher
(1845-1914),
a
lawyer.
The Ansbachers
were
close friends of the
Einstein
family
in Milan.
[4]Angelo
Battelli
(1862-1916);
Annibale Stefanini
(1855-?);
Battelli and
Stefanini 1899.
[5]The
parameter i
was
introduced
by
Jacobus van
't
Hoff
(1852-1911) in
his
theory
of
os-
motic
pressure to
account
for the difference between the actual osmotic
pressure
of
a
solution
and the ideal
gas
law. Thus,
the osmotic
pressure
p
for
n
moles of solution
in
a
volume
V
fol-
lows from
pV
=
inRT
(see
Van 't Hoff
1885). In 1887
Arrhenius made
a
connection between
the
parameter
i
and the number of
ions in
which
a
molecule of
an
electrolyte
is
dissociated
(see
Arrhenius
1887).
[6]I.e., through
the determination of the
freezing point.
[7]Frangois
Marie Raoult
(1830-1901);
Svante
Arrhenius
(1859-1927).
Raoult
1888a,
Raoult
1888b,
Arrhenius 1887, Arrhenius 1888a, Arrhenius 1888b.
[8]Gustav
Tammann
(1861-1938); Tammann 1887.
[9]I.e.,
through
the determination of the
boiling point.
[10]Ernst
Beckmann
(1853-1923);
Beckmann
1890.
[11]Wilhelm
Ostwald
(1853-1932);
Ostwald 1887.
[12]Friedrich
Kohlrausch
(1840-1910);
Kohlrausch 1879.
[13]Max
Roloff; Roloff 1902.
[14]William Sutherland
(1859-1911) proposed
an
explanation
for osmotic
pressure
in which
a
semipermeable
barrier
was
represented
as a
mesh that holds back the molecules of the solute
because
of
their size,
while the
(smaller)
solvent molecules
can
pass freely
(see
Sutherland
1897).
[15]Einstein's
interest in
semipermeable
membranes shows
in
Einstein 1902a
(Vol. 2,
Doc.
2),
in
which
he
mimics their effects with external conservative forces.
[16]See
the
two
enclosures.
[17]Jacobus
van
't
Hoff
postulated
that
in
solid solutions the solute exerted
an
osmotic
pres-
sure, analogous
to
the osmotic
pressure
in
fluid solutions
(see
Van 't Hoff 1890).
The observed
phenomenon
of
the
diffusion of
the
solute into the solid seemed
to
support
this idea.
See
Nernst
1898,
pp.
167-170 for
a
contemporary
discussion of solid solutions.
[18]A
possible
relation between
gravitational
and molecular forces
was
also
a
topic
of
spec-
ulation
in
Einstein's first
published paper
(see
Einstein
1901
(Vol. 2,
Doc.
1),
p.
523). See
Vol.
2,
the editorial
note,
"Einstein
on
the Nature of Molecular
Forces,"
p.
6
for
more
details.
[19]Ostwald's
dilution
law,
which
predicts
a
simple
relation between the
degree
of ionization
of
an
electrolyte
and
the molar
density
of the
solute,
proved to
be valid
only
for weak electro-
lytes.
As
a
possible explanation
of this failure it had been
postulated
that the ions of
the
solute
combined with solvent molecules
to
form various kinds of
aggregates ("hydration").
This
hy-
pothesis
was
not
undisputed
at
the
time;
see, e.g., Bousfield
1905 for
a
contemporary
discus-
sion.
When
in 1905
Einstein
wrote
his dissertation
on
the determination of molecular dimensions
(Einstein 1905j
(Vol.
2,
Doc.
15)),
the method
he
chose
(a
determination of the effect of the
size of the solute molecules
on
the
viscosity
of
a
solution)
allowed him
to
conclude that
hy-
dration did indeed take
place.
He later claimed that
a
solution of the
hydration
question
had
been
a
motivating
factor
in
his choice of
viscosity
as a
tool
to study
the size of molecules
(see
Doc.
186).
For
more
details,
see
Vol.
2,
the editorial
note,
"Einstein's Dissertation
on
the De-
termination of Molecular
Dimensions,"
pp.
170-182.
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