Cell constant:

To a given cell, l and A are constant, and the quantity (l/A) is called the cell constant (k).

K_cell   = L/A

Substitute this value in Eq. (4.5)

κ =  G K_cell                                                                              ... (4.6)

Conductivity = observed conductance × cell constant

To obtain the value of the cell constant, it is not essential to determine l and A directly. Instead, it is measured by a solution of known conductivity. Potassium chloride solutions are invariably used for this purpose, since their conductances have been measured along with enough accuracy in cells of known dimensions. A provided explanation of potassium chloride of conductivity κ ′ is placed in the cell and its resistance R' is measured. The cell constant is then equal to κ ′ R'. Therefore,

Kcell = κ ′ R'

Cell constant = conductivity KCl solution × measured resistance

Conductance is an additive property, example for. In an aqueous solution containing several electrolytes, the whole conductance is

G(total)   =   ΣGi   +  G (water)       ... (4.7)

where the summation is to be contained over all the electrolytes present in the solution and G (water) is an conductance of water, which is utilized for making the solution.

G (water) is often negligible in comparison to ΣGi as repeatedly distilled water (known as conductivity water) of very low conductance is employed for making the solutions.