502 DOC. 50 BROWNIAN MOTION

and

of Planck's

theory

of

black-body

radiation

are

close to the value

given by

Einstein here

(see,

for

e.g.,

Meyer,

O. E.

1899,

p.

337,

and

Planck

1901b).

This

is

the first time

in

his

papers

on

Brownian motion that Einstein noted this dis-

crepancy.

[7]

For

a

determination

of

molecular

dimen-

sions from data

on

diffusion that

is

based

on

an

argument

similar to Einstein's,

see

Sutherland

1905.

[8]

This

assumption

is

the main

simplification

in this

paper compared

to

Einstein's

previous

work

on

Brownian

motion,

in which the

dis-

placements

are

determined

by a probability

dis-

tribution

(see

Einstein

1905k

[Doc. 16], p. 556,

and Einstein 1906b

[Doc. 32], p. 377).

[9]

The

correct

expression

is

"VT2."

[10]

This

equation was

first derived

in

Einstein

1905k

(Doc. 16),

p.

559.

[11]

Einstein 1907c

(Doc. 40).

[12]

The value for the

viscosity

of

water is

ac-

tually given

for the

temperature

9.5°C

(as

in

Ein-

stein

1905j [Doc. 15], p. 21).

The

particle

size

is that assumed in Einstein 1905k

(Doc. 16),

p.

559.

[13]

See note

6.

[14]

The

same

value for the diffusion

constant

was

used in Einstein

1906c

(Doc. 33),

pp.

305-

306.

[15]

For the size

of

a sugar

molecule,

see

also

Einstein

1905j

(Doc. 15).

[16]

This sentence should be:

"Für

Ionen kön-

nen

wir

A

aus

ihrer

Wanderungsgeschwindigkeit

l...."

For

a contemporary

discussion

of

the

concept

of

migration velocity

of

ions,

see

Nernst

1898,

pp.

352-353; for

a comprehensive ac-

count,

see Bredig

1894.

[17]

This

equation

follows from

Faraday's law;

for

a contemporary survey

of

its

history

and

of

its

applications,

see

Ostwald

1893,

pp.

579-

592.

[18]

The units

of

k

are dynes.

[19]

In

Landolt and

Börnstein

1905,

p.

763,

the

migration velocity

for

hydrogen

at

18°C is

given

as

318,

and that for

potassium

at

the

same

tem-

perature as

64.7.

The

migration velocity

for

the

"Diisoamylammoniumion"

at 25°C is listed

in

Bredig 1894,

p.

228,

as

24.2.