Intermediate Topic 603 of 1102 Acids, Bases & Electrochemistry
pH Meter
Measures potential across a glass electrode to give pH.
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In-depth explanation of pH Meter
A pH meter measures the potential difference between a glass electrode, whose potential depends on hydrogen ion activity, and a reference electrode of constant potential. The response is close to the Nernstian value of about 59 mV per pH unit at 25 C, so the meter converts millivolts into pH. Because the electrode response drifts with time and temperature, the meter must be calibrated with buffer solutions of known pH before measurement. Temperature correction is also needed for accurate results. pH meters are used in laboratories, water treatment and industrial process control.
Going deeper: pH Meter
Key ideas: A glass electrode (thin H+-sensitive glass bulb) and a reference electrode (Ag/AgCl) measure the potential difference, E = const - 0.0592 pH at 25 C, so each pH unit gives 59.2 mV. Calibrate with two or three buffers (such as 4.01, 7.00, 10.01); slope should be 95 to 105 percent of ideal. Keep the bulb hydrated in storage solution.
Common mistakes and connections: Mistakes: not calibrating near the sample pH, ignoring temperature compensation, dry storage, and the alkaline error above pH 12 (Na+ interference) and acid error below pH 1. Contaminated junction gives drift. The reading reflects activity of H+, not concentration. A sample at 0.1 M ionic strength shifts the reading slightly.
Visualization of pH Meter
A glass electrode responds about 59 mV per pH unit at 25 C; the meter converts this potential to pH after calibration with buffers. The interactive lesson shows this as a live animation or chart.
Worked example and use case
A pH meter should be calibrated with pH 4, 7 and 10 buffer solutions before measuring an unknown sample.
Frequently asked questions about pH Meter
What is pH Meter?
Measures potential across a glass electrode to give pH.
Is pH Meter a beginner, intermediate or advanced topic?
pH Meter is a intermediate topic in Acids, Bases & Electrochemistry. It builds on the vocabulary of beginner topics in this area.
What should I learn before pH Meter?
Study these earlier topics in Acids, Bases & Electrochemistry first: Pourbaix Diagram, Latimer and Frost Diagrams, Ion-Selective Electrodes.
What comes after pH Meter?
The next topics in Acids, Bases & Electrochemistry are Hydrogen Production by Electrolysis and Acid Rain.
Can I practise pH Meter with quizzes?
Yes. The interactive lesson includes a self-check question on pH Meter, and the Acids, Bases & Electrochemistry quiz draws on every topic in this area.
Where pH Meter fits in Acids, Bases & Electrochemistry
pH Meter is topic 93 of 105 in Acids, Bases & Electrochemistry.