DETERMINATION OF PH OF A SUBSTANCES

DETERMINATION OF PH

Introduction

pH determination is one of the test most frequently carried out on water samples. The PH determination of water is a relatively reliable indication of its acidic of alkaline tendency. It is not the measure of the quantity or acidity or alkalinity in a water sample. A PH value of less than 7 shows a tendency towards acidity while a value greater than 7 shows a tendency towards alkalinity. PH is represented on the PH universal scale of numbers 1 – 14 shown below.

1	2	3	4	5	6	7	8	9	10	11	12	13	14

←Increasing Acidity                  Neutrality                    Increasing Alkalinity→

Definition

PH is the negative logarithm of the Hydrogen ion concentration

PH     = -log(H⁺)

Scope

This test method covers the determination of PH by electrometric measurement using the glass electrode the sensor.

APPARATUS

• ·     pH meter

• ·        Beaker

• ·        Buffer solution

Fig 2.5: PH Meter

PROCEDURE

•       Calibrate the PH meter with buffer 4, 7, and 10 solutions.

•         Rinse the electrode with distilled water each time before   dipping it in the buffer solution.

•         Dip the glass electrode in the sample.

•         Take your reading on the meter as indicated by the pH meter.

•    Record the reading of the pH meter indicating the temperature.

Precautions

•        Calibrate the instrument before usage.

•          Rinse the electrode properly with distilled water before usage.

•           Do not use expired buffer solutions for calibration.