Determination of PH of Water

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Aim

To determine the pH of the given water sample.

Apparatus

Burette, pH paper, pH meter, Glass Beaker, Buffer tablets.

Reagents

Standard Buffer solutions

Theory

pH is defined as the negative logarithm of hydrogen ion concentration or logarithm of reciprocal of hydrogen ion concentration. Measurement of pH 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 pH dependent. pH of drinking water should be in the range of 6.5 to 8.5.

Procedure

  1. . By pH Paper Method

Tear off a piece of pH paper from the pH 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 pH paper book and record the pH. This  method  is  an  approximate method only.

  1. . By pH meter Method (Electrometric method)
  2. Check the inside of the electrode of the pH 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 pH 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 pH 4. Press the knob to adjust it to read pH 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 pH directly.

Observation

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