PH's principle of electrical measurement:
The basic principle of measurement
The traditional measurement of pH of aqueous solutions with glass electrode as indicator electrode and calomel electrode as reference electrode, when the hydrogen ion concentration in the solution (strictly speaking is the activity that) the pH value of the solution changes, generated between the glass electrode and calomel electrode potential with the change of the relationship and potential changes in accordance with the following formula:
Delta E=-0.1983T Delta pH.
The E said the potential changes in MV units (mV).
PH said: the change of pH value of solution.
T - the temperature of the measured solution (centigrade).
The commonly used indicator electrodes are glass electrodes, antimony electrodes, fluorine electrodes, silver electrodes and so on, among which glass electrodes are the most widely used. PH glass electrode head is made of special sensitive films, it is sensitive to hydrogen ion, when it is inserted into the measured solution, its potential is changed with the hydrogen ion concentration and temperature in the solution. When the temperature of the solution is 25 C, each change of 1 pH, the electrode potential changes 59.16mV. This is the theoretical slope coefficient that is often described as the electrode. Commonly used as reference electrode and calomel electrode, the electric potential with hydrogen ion concentration in the solution was changed. The essence of the pH measurement is to measure the potential difference between the two electrodes. When a pair of electrodes is in the solution
When the potential difference is equal to zero, the pH value of the measured solution is zero potential pH, which is related to the solution in the glass electrode. The instrument is composed of a composite electrode consisting of a glass electrode and a Ag-AgCl electrode, with a zero point position of 7 + 0.25pH.