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Measuring

FAQ | Measuring
Questions Answers
Should you stir during the ph measurement or not? What are the pros and cons? This depends on the electrode you use. Electrodes with platinum diaphragms do not show any or only a very minor stirring effect; therefore, they influence the measured potential. Electrodes with ceramic diaphragms show a higher stirring effect. The advantage (pro) is the better mixing of the measuring medium. In order to keep this increased influence on the diaphragm as low as possible, shortly stir to mix the solution and then perform the measurement without stirring.
Why should the refill opening of the electrode be open during ph measurement? The open refill opening causes a pressure balancing. The KCl solution can flow out through the diaphragm into the measuring solution. At the same time, it prevents the submersion of the measuring solution through the diaphragm. This keeps the potential of the inner electrolyte unchanged.
Do I have to calibrate at the same temperature that I am measuring at? The calibration and measurement should be performed at the same temperature for the most precise result.
Which buffers should be used for calibration? It is impossible to achieve a higher accuracy than the accuracy of the buffer solutions. Therefore, the user must determine which accuracy is required for his measurement and then adapt the buffer solutions for the calibration. STATEMENT?
What do I have to watch out for with an electrode, so that it measures properly (opening the air supply, discolorations, diaphragm, replacing the inner electrolyte)? Regular calibration to verify whether the electrode is still measuring correctly. Visual inspection of the diaphragm for discoloration, the refill opening must be open for the measurement, replace the inner electrolyte if it has crystalized or discolored.
Which buffers are the best ones to use for the calibration? Buffer solutions in the acidic or neutral range, as alkaline buffer solutions quickly change their buffer value due to picking up CO2 contained in the air and can thus lead to miscalibrations.
Why temperature indication with ph in spite of temperature compensation? Why is T-Cal = T Meas? The temperature compensation of the measuring devices can only be calculated with the temperature dependency of the "Nernst factor", as the temperature dependency of the sample is usually unknown.