20
normal to the current flow (A):
Therefore, conductivity equals conductance multiplied by the cell constant.
Example: For an observed conductance of 100 micro mhos (100 microsiemens) and a cell
constant of 0.1/cm
= k
K
= 100 mho
0.1 / cm
= 10 mho / cm
ℵ
×
×
µ
µ
In SI units, the cell constant K=0.1/cm would become K=10/m, and the same conductivity would
be expressed:
Cell Constant
The cell constant (K) is used to determine the resistivity or conductivity of a solution. It is
defined as the ratio of the distance between
electrodes (d) to the area normal to the
current flow (A). Cells with constants of
1.0/cm or greater normally have small, widely-
spaced electrodes, while cells with constants or
0.1/cm or less have larger electrodes that are
closely-spaced.
Cell Constant = K =
d
A
ℵ
ℵ
ℵ
ℵ
= k
K
×
ℵ
×
×
= k
K
= 100 S
10 / m
= 1 S / m
µ
m
