Laboratory Experiments of B.Sc. II Sem BT/FS/CBZ - Experiment: 3

 Laboratory Experiments of B.Sc. II Sem BT/FS/CBZ

 

Dr. Navdeep Sharma
Institute of Sciences
SAGE University, Indore (M.P.)

 

Experiment 3


Objective:

To calibrate a pH meter using standard buffer solutions of known pH values.

Apparatus and Materials Required:

  • Digital pH meter
  • Standard buffer solutions (pH 4.00, pH 7.00, and pH 9.20 or 10.00)
  • Distilled water
  • Beakers (3) – 50 mL each
  • Wash bottle
  • Tissue paper or filter paper
  • Glass rod
  • Measuring cylinder

Theory:

A pH meter measures the hydrogen ion concentration (acidity or basicity) of a solution. Calibration ensures accurate and reliable readings by setting the pH meter to known pH values before use. Buffer solutions with known pH values are used for calibration. Usually, a 2-point or 3-point calibration is performed.

Procedure:

  1. Preparation:
    • Switch on the pH meter and allow it to warm up for 5–10 minutes.
    • Rinse the electrode with distilled water and blot dry using tissue paper (do not rub).
  2. Calibration with pH 7 Buffer:
    • Pour a small amount of pH 7.00 buffer solution into a clean beaker.
    • Dip the electrode into the buffer solution and wait for the reading to stabilize.
    • Set the meter to read exactly pH 7.00 using the calibration knob.
  3. Calibration with pH 4 or pH 10 Buffer:
    • Rinse the electrode with distilled water and blot dry.
    • Pour pH 4.00 (for acidic range) or pH 10.00 (for basic range) buffer solution into a clean beaker.
    • Dip the electrode into the solution and allow it to stabilize.
    • Adjust the second calibration knob (slope) to read exact pH value of the buffer.
  4. Verification (Optional):
    • Repeat with a third buffer (e.g., pH 9.20) to check the accuracy.
  5. Final Rinsing:
    • Rinse the electrode again with distilled water.
    • The pH meter is now calibrated and ready for use.

Precautions:

  • Always use fresh standard buffer solutions.
  • Do not wipe or rub the electrode; gently blot dry.
  • Avoid contaminating the buffer solutions.
  • Keep the electrode immersed during use and store in suitable storage solution.

Result:

The pH meter was successfully calibrated using standard buffer solutions. It can now be used for accurate pH measurements.

 

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