Determination of pH.

 Dear Students,

This post discuss the pH determination by colorimetric method. Two videos are attached for easy understanding.

Determination of pH:

pH determination measures the acidity or alkalinity of a solution using pH paper, indicators, or a pH meter to find hydrogen ion concentration. 

Methods: 

Electrometric Method (pH Meter): This is the most accurate method, utilizing a glass electrode to detect electromotive force (EMF) generated by hydrogen ions, often utilizing two- or three-point calibration with buffer solutions.

Colorimetric Method (pH Paper/Indicators): A less precise method involving pH paper or universal indicators that change color, which is then compared against a standard chart.

Working Principle:

The pH is measured by noting the various colour changes in this method. A universal indicator (e.g., B.D.H. universal indicator) and various buffer solutions in the pH range 3 to 11 are prepared. A drop of universal indicator is added to each buffer solution and the colour change is noted. Then, few drops of universal indicator are added to the solution of unknown pH. The colour of this solution is compared with the suitable buffer solution and the pH may be determined. Comparators are employed for the matching of colour tints. Hellige comparator is generally used in water analysis.