Traditional pH electrode

As illustrated in Fig, 1, when two solutions with different pH values are separated by a pH-sensitive glass membrane, a potential difference develops that can be measured by chemical half-cells as a voltage change across the membrane. The reference half-cell, usually composed of mercury/mercurous chloride (calomel) housed in a compartment filled with potassium chloride solution, supplies a constant reference voltage. The measuring half-cell is a Sanz electrode, usually composed of a silver/silver chloride substance embedded within a pH 6.840 buffer chamber. A contact bridge consisting of a potassium chloride solution completes the electronic circuit.

Fig. 1 Basic principles of the pH electrode: (a) a voltage develops across pH-sensitive glass when pH is unequal in the two solutions; (b) chemical half-cells used as measuring and reference electrodes; (c) the pH electrode system completed by a device measuring voltage changes. (Reproduced with permission from Shapiro et al. (.,19.94),)

The relationship between the potential difference Eu - Ek and the pH values of the known (pHk) and unknown (pHu) solutions is defined by the Nernst equation:

Was this article helpful?

0 0
Sleep Apnea

Sleep Apnea

Have You Been Told Over And Over Again That You Snore A Lot, But You Choose To Ignore It? Have you been experiencing lack of sleep at night and find yourself waking up in the wee hours of the morning to find yourself gasping for air?

Get My Free Ebook

Post a comment