Question

Discuss the method used to measure the electrolytic conductivity of a solution.

Answer 1

The electrolytic conductivity or specific conductivity, kappa (κ), of a solution is measured using a conductivity cell and a Wheatstone bridge arrangement or conductivity meter.

1. Conductivity cell: A glass cell with two platinum electrodes coated with platinum black is used. The electrodes are placed at a fixed distance apart and dipped in the solution.  It is determined using a standard solution (usually KCl of known conductivity). The cell constant is defined as

Cell constant = `"Distance between electrodes"/"Area of cross section of electrodes"`

= `l/A`

It is determined using a standard solution (usually KCl of known conductivity).

2. Wheatstone Bridge: Alternating Current (AC) is used (not DC) to avoid electrolysis and polarisation. The conductivity meter measures the resistance (R) of the solution. 

Once resistance (R) and cell constant are known, conductivity is calculated as

κ = `"Cell constant"/R`