Construction of pH Electrodes

1. Glass pH electrodes are Widely used pH electrodes these are composed of glass tubes ended with a small glass bubble.

2. A buffered solution of chlorides is loaded within the pH electrodes. A silver wire coated with silver chloride is steeped inside this solution.

3. The pH value of the intimate solution is ranges- for example, it can be 1.0 (0.1M HCl. or 7.0 (various buffers employed by various producers..

4. The glass bubble is the active part of the electrode.

5. The tube portion of the electrode contains a strong and thick wall, whereas the bubble contains a thin wall.

6. Both the internal and external solutions protonate the glass surface until equilibrium is achieved. The adsorbed protons charged both sides of the glass which is responsible for potential differences.

7. This potential in aid is defined by the Nernst equation and is directly equivalent to the pH variation between solutions on both surfaces of the glass.

8. Most of the pH electrodes obtainable commercially are compound electrodes that contain both glass H+ ion-sensitive electrodes and further reference electrodes conveniently installed in a single housing.

9. Separate pH electrodes and reference electrodes are still accepted for specific applications. They provide immense accuracy required sometimes for research purposes. The compound electrodes are very accurate and much more comfortable to practice.

10. The development of a compound pH electrode is in huge part determined by the processes that must take place when estimating pH. We require to estimate the variation of potentials within surfaces of glass in the glass electrode. To do so we require a closed circuit.

11. The circuit is locked within the solutions – internal and external – and the pH meter. Though for accurate and constant returns of estimations reference electrodes must be separated from the liquid so that they will not crosscontaminate – and it is not an easy job to attach and detach two solutions at an identical moment.

12. The electrode body contains a small hole which makes this connection possible. This hole is prevented by a permeable membrane or ceramic (asbestous in older models. wick.

13. The Internal liquid moves very gently through the junction, therefore such electrodes are designated as flowing electrodes. To reduce the leaking, in gel electrodes internal solution is gelled.