Application of Coulometry:

The basic relationship used in calculating the amount of the substance in a solution is given through

m = M_r ×/96500×

where M_r is the associative molar molar mass of the substance to be electrolyzed and n is the number of electron moles included within the electrode reaction, m is the mass of the substance generated or consumed in an electrolysis including Q Coulomb (Q = I × t, where I is the current in amperes and t is the time is seconds).

Generally, coulometry is of two types same to electrogravimetry:

1.         Coulometry along with controlled potential of the working electrode.

2.         Coulometric analysis with constant current.

Within the first case, the substance of interest must reacts with 100 % current efficiency at a working electrode, a potential of that is controlled. The completion of the reaction is denoted through the current decreasing to practically zero and the amount of substance produced or consumed at the electrode is determined from the reading of a coulometer in series with the cell or with the help of a current-time integration device.

Within the second method, i.e. coulometery at constant current, a solution of the substance to be determined is electrolyzed with constant current until the reaction is completed as determined with the help of a suitable indicator in the solution, or using amperometric, potentiometric or spectophotometric techniques.

Quantity of the electricity passed Q = current (amperes) × time (seconds).

Time could be measured accurately either along with an accurate electric stop-clock or a slow inertia integrating moter-counter unit