Determination of pH by colorimetric method

A colorimetric method of pH determination is presented to measure the pH of a liquid/aqueous solution with the accuracy of pH unit 0-01. It is emphasized that the apparent pH measured by the sulfonphthalein indicators is not the same amount as that obtained electrometrically. The advancement of glass electrodes, involved in the pH meter, has made the electrometric method the most common way of measuring pH.

As it can be applied in a very dilute solution, colloids and colored solution, where the indicators are inconvenient, in addition to these particular cases, the indicators bring certain advantages, and it seems to us a mistake to consider that the electrometric method is a method standard, and always the most accurate. The simple comparator is used, a reproducibility unit of about 0-01 pH is easily provided by an indicator.