Determination of PH of Water

Aim

To determine the p^H of the given water sample.

Apparatus

Burette, p^H paper, p^H meter, Glass Beaker, Buffer tablets.

Reagents

Standard Buffer solutions

Theory

p^H is defined as the negative logarithm of hydrogen ion concentration or logarithm of reciprocal of hydrogen ion concentration. Measurement of p^H is one of the most important and frequently needed tests in water and waste water engineering. Practically every phase of water supply and wastewater treatment, for example acid base neutralization, water softening, coagulation, disinfection and corrosion control is p^H dependent. p^H of drinking water should be in the range of 6.5 to 8.5.

Procedure

1. . By p^H Paper Method

Tear off a piece of p^H paper from the p^H paper book. Dip this paper in a test tube filled with the given water sample. Allow this paper to dry and develop color. Compare the colour with the standard colour printed on the cover of the p^H paper book and record the p^H. This  method  is  an  approximate method only.

1. . By p^H meter Method (Electrometric method)
2. Check the inside of the electrode of the p^H Meter to ascertain whether it contains sufficient level of saturated KOH solution. The two electrodes are always immersed in distilled water.

    

3. Set the temperature to 25°C (room temperature). Switch on the p^H Meter and allow the meter to warm up for about 15 minutes.

    

4. Take out the electrodes from the distilled water, rinse it and clean with a tissue paper and immerse them in standard buffer solution of say p^H 4. Press the knob to adjust it to read p^H position using the calibrating knob.

    

5. Repeat the procedure with the second buffer solution. If the meter shows the correct reading directly, the instrument is calibrated

    

6. Place the electrodes in the given water sample and record the p^H directly.

Observation