Indian Council of Agricultural Research
(Agricultural Knowledge Management Information System)

ICAR-Central Island Agricultural Research Institute, PB No. 181, Port Blair-744101, Andaman & Nicobar Islands (
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Instrument Details
Instrument/Facility Name: pH Meter
Make                                   : HANNA
Model                                  : HI2002-02
Specification   :Serial No C0301050, Purpose- Mineral Analysis

Click to ViewpH Meter is very commonly used for the measurement of the reaction of a solution or a medium. The pH determine with help of a PH metere is based on the measurement of the electromotive force (e.m.f) of a pH consisting of an electrode sensitive to H+ ions and a reference electrode. The conventional type of pH meters have H+ sensitive glass electrode and a calomel reference electrode. The other types of H+ sensitive electrode are hydrogen gas electrode, platinum electrode, quinhydrone electrode and antimony electrode.

  Working Principles
Click to ViewA pH meter is used to determine the acidity or alkalinity of the solution. pH is the concentration of hydrogen ions in the solution. A solution containing more H+ ions remains acidic while the solution containing more OH- ions remains alkaline. pH value of solutions ranges from 1 to 14. pH electrodeSolution having pH value 1 will be the highly acidic and with pH value 14 will be highly basic. The acidity and alkalinity of any solution depends upon the concentration of hydrogen ions (H+) and hydroxyl ions (OH-) respectively. A neutral solution as pure water has pH 7. pH meter is used to determine the pH of different solutions in pharmaceuticals. It is more accurate method then the pH strip. A pH meter contains a pH probe that passes the electrical signals to the pH meter and pH meter displays the pH value of the solution. The glass pH probe contains two electrodes, a sensor electrode and a reference electrode. These electrodes are in the form of glass tubes one contains pH 7 buffer and other contains saturated potassium chloride solution. The sensor electrode bulb is made up of porous glass or permeable glass membrane coated with silica and metal salts. A silver wire coated with silver chloride is immersed in pH 7 buffer in the bulb. Another silver wire coated with silver chloride is immersed in the saturated potassium chloride solution in reference electrode . Parts of pH electrode When the probe is placed in a solution to measure the pH, hydrogen ions accumulate around the bulb and replace the metal ions from the bulb. This exchange of ions generates some electric flow that is captured by the silver wire. The voltage of this electric flow is measured by the pH meter by converting it into pH value by comparing the generated voltage with the reference electrode. Increase in acidity of solution has greater concentration of hydrogen ions that increases the voltage. This increased voltage decreases the pH reading in pH meter. In the same manner an increase in alkalinity decreases the hydrogen ions or increases in hydroxyl ions concentration also decrease the voltage and increase the pH value in pH meter. Overall pH meter principle of pH sensor and pH meter depends upon the exchange of ions from sample solution to inner solution (pH 7 buffer) of glass electrode through the glass membrane. Porosity of the glass membrane decreases with the continuous use that decreases the performance of the probe.

  User Instructions
The most delicate part of pH meter is the glass electrode. The thin walled glass blub very often breaks due to rough handling. It may also dry up when kept out of water for long. If dried, the electrode should be immersed first in 0.1 NHCl and then in distilled water for one or two days and checked again for its sensitivity. For general care attention may be paid to some tips which are as follows: 1. For checking the defect in electrode , short circuit the electrode jacks with the special strap and provide the terminal connections with the instrument. Switch on the instrument and allow 15-20 minutes for warm up. If the galvanometer reads 7.0 or can be adjusted at pH 7.0, the defect lies in electrode. Replace the electrode in such case. 2.Ensure that there is always some solid KCI in the reference (calomel ) electrode. 3. Remove the fine layer of clay gels, deposited on the electrode, if any, with the help of cotton wool and distilled water. 4. Keep a pair of glass and calomel electrode as spare for emergency use.

  Contact Us
Contact No. 03192- 250341
Email Id

  pH Meter Charges
Procedure Name
National LAB/R&D

Additional Rs 100/-towards postal charges if result are to be posted
The Demand Draft should be in favour of "The Director CIARI, Payable at Port Blair"
Letter, DD & Samples send to " ICAR-Central Island Agricultural Research Institute Post Box No# 181 Port Blair -744 101 Andaman & Nicobar Islands"