Page 50 - Pharmaceutical Analytical Chemistry II - Pharm D- 02-06-07102

- Reference electrode --- works as anode (left half-cell)
- Voltmeter to measure the potential difference between the

indicator electrode and the reference electrode

Potentiometric Cell

Equation for direct potentiometry
Ecell = Eindicator − Ereference

REFERENCE ELECTRODES

Ideal reference electrode:
- It has well defined, stable, and reproducible potential
- Its potential is stable at all temp
- Its potential is insensitive to the composition of the analyte

solution
- Easily constructed, Inexpensive and safe
Examples

- Standard Hydrogen electrode
- Calomel reference electrode
- Silver/silver chloride reference electrode

Calomel Electrodes

A calomel electrode can be represented as:
HgHg2Cl2 (sat’d) , KCl (xM)
Three concentrations of KCl are common, 0.1 M, 1M, and
saturated (4.6 M)
The electrode potential is determined by:

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