Procedure:

Numerous  pH  meters  of  various  designs  are  marketed  by  several  instrument manufactures. Common reasons pH meters are either line operated instruments that are readable to 0.05 pH battery or unit operated instruments suitable for field job. These days' digital pH meters readable to 0.01 pH unit are most popular as compared to scale-needle instruments.

With the instrument Measurement of pH of a solution (analog meter) shown in Figure can be made following the procedure given below in a step-wise manner.

1. Keep the selector switch on 'zero' position and adjust the zero position by a screwdriver if the pointer does not indicate zero.

2. Before using pH meter, remove electrodes from storage solutions (recommended by manufacturer) and rinse with distilled water. Dry electrodes by gently blotting with a soft tissue paper.

3. Mount the electrodes in the clip on the stand.

4. Connect the power cable to a 220V AC supply.  Switch on the instrument and wait for a few minutes till the instrument warms up.

5. Adjust the temperature/solution temperature value.

6. Take the standard buffer solution of desired range (e.g. buffer of pH 4 for acidic solutions) in a beaker.  An electrode assembly is immersed in the pH reference buffer and the solution is agitated gently by swirling the solution in the region of the glass electrode surface so as to bring it into pH equilibrium. It should be ascertained that the glass electrode membrane is completely immersed in the solution. The electrodes should not touch each other or the side or the bottom of the beaker.