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P h glass electrode

The document summarizes the pH glass electrode, which is used to measure pH through the detection of hydrogen ion activity. It functions as a fast responding, hydrogen ion selective electrode. The electrode contains a lithium silicate glass membrane that forms a hydrated gel layer, allowing only hydrogen ions to penetrate and alter the electrochemical potential between the glass and reference electrode. It is able to measure pH based on the Nernst equation, with the potential changing approximately 60mV for every unit change in pH.

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pH Glass Electrode
Uses of the Glass Electrode • pH measurement • analyze foods • Cosmetics • environmental regulations • soil acidity It is fast responding and functions well in physiological systems (Biological Systems).
Construction of pH Glass Electrode + - Ag/AgCl reference electrode Glass pH electrode
Two Electrode System
The Gel Layer • The glass has a lithium silicate skeleton that forms a thin hydrated layer on both sides of the membrane. • Ions can penetrate this thin layer and alter the electrochemical potential. • Without the hydrated layer no pH measurements would be possible • The structure of the glass has been optimised so that virtually only H+ ions can enter the gel layer
Principle • H+ ion selective electrode • Nernst Equation log( aH + ) 2.303RT E=E −0 nF • the electrode measures the activity of hydrogen ions and that pH is the E = E 0 + 0.0591 pH @ 25o C negative log of the activity of hydrogen ions • The Nernst equation predicts that for every decade change in H+ ion activity (1 unit change in pH) the potential will change by about 60 mV
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