
55-16 Chemical Variables
e proportionality factor D is called the diusion coecient. At the electrode surface, the ux must be
eq
ual
to t
he
n
umber
o
f
m
oles
N c
onverted
p
er
u
nit
o
f
t
ime
a
nd
s
urface
a
rea
b
y
t
he
e
lectrode
r
eaction:
j t
N
t
( , )0 =
d
d
(5
5
.24
)
e
f
aradaic
c
urrent
i
f
is related to dN/dt according to
i
nFA N
t
f
d
d
=
(5
5
.25
)
where
n i
s
t
he
n
umber
o
f
e
lectrons
i
nvolved
i
n
t
he
r
eaction
o
f
a si
ngle
a
nalyte
p
article
F i
s
t
he
F
araday
c
onstant
a
nd
A i
s
t
he
s
urface
a
rea
o
f
t
he
w
orking
e
lectrode
e Ne
rnst diusion layer
mo
del
as
sumes
th
at
wi
thin
a la
yer
of th
ickness
δ, th
e
an
alyte
co
ncentration
de
pends
li
nearly
on th
e
di
stance
fr
om
th
e
el
ectrode