pH value

pH value definition :

  • The meaning of pH value “Sörenson” states that the pH is equal to the negative (base 10) logarithm of the concentration of the ion H+, or pH = – log [H+].
  • The pH value fluctuates by one unit for every ten-fold variation in the H+ ion concentration. This demonstrates how crucial it is to have accurate pH measurement to the tenth of a unit (or even a hundredth of a unit in critical cases).

Below figure is pH Scale (Ref.,

pH Scale
pH Scale (Ref.

Related: Calibration of pH Meter, Why are pH values mostly in A Range of 0.0 to 14.0?

How can we convert pH to mV?

  • The millivolts (mV) to pH formula were first revealed by Dr. Jerry Tennant.
  • pH Voltage: To measure the manually any one can measure by making difference of 57.14 mV in 1 pH difference.
  • Example:
    • If 7.0 pH have 0 mV reading than ideally 8.0 pH will be -57.14 mV and 6.0 pH will be +57.14 mV

The below table enlist the pH value and pH voltage in mV

0 pH+400mV
1 pH+342.86 mV
2 pH+285.71 mV
3 pH+228.57 mV
4 pH+171.43 mV
5 pH+114.29 mV
6 pH+57.14 mV
7 pHzero mV
8 pH-57.14 mV
9 pH-114.29 mV
10 pH-171.43 mV
11 pH-228.57 mV
12 pH-285.71 mV
13 pH-342.86 mV
14 pH-400 mV
pH value and mV value

What is offset value in pH meter?

  • The offset error, which can be as high as 25.0 mV, is the difference between the electrode’s actual reading and 0 mV. In other words, the output (or reading) will be referred to as the offset when the electrode is not in measurement mode or in pH 7 buffer solution.

Process of Regeneration of pH Electrode

  1. Check the solution inside the electrode. It should be filled with suitable solution.
  2. Use cotton wool soaked in acetone (Take care during using Acetone as it is “HAZARDOUS SUBSTANCE”) or soap solution to remove oil from the membrane. Electrodes with plastic bodies shouldn’t be cleaned with acetone.
  3. Overnight membrane soaking in 0.1 M HCI
  4. If previous measurements on pH meter have been made in samples with protein, remove these deposits by soaking the pH electrode bulb in 0.1 M HCl and pepsin solution beaker.
  5. Immerse the electrode in an ammonium bifluoride regeneration solution.
  6. If all these fails, the pH electrode should be changed with a brand new electrode


pH meter – Wikipedia

Mettler Toledo and HACH.

Read More:

You cannot copy content of this page