The key difference between pH and titratable acidity is that the pH measures the concentration of free protons in a solution whereas titratable acidity measures the sum of free protons and un-dissociated acids in a solution.
The acidity of a solution measures the ability of that solution to neutralize a base. This is because acids contain dissociable protons (H+ ions) and bases can release OH- ions. When the acid reacts with the base, the H+ ions and OH- ions react with each other to form water molecules (H2O). Hence, it is a neutralization reaction.
CONTENTS
1. Overview and Key Difference
2. What is pH
3. What is Titratable Acidity
4. Side by Side Comparison – pH vs Titratable Acidity in Tabular Form
5. Summary
What is pH?
The pH is a measurement of the concentration of free protons (H+ ions) in a solution. These protons are the H+ ions that dissociate from acids. Therefore, by measuring the pH of a solution, we can measure the acid strength of a solution. It means that we can measure the capability of that solution to neutralize a base. If a solution is acidic, the pH value is less than 7. But if the solution is alkaline, the pH of that solution is above 7.
Figure 01: pH Scale
We consider the pH 7 as the neutral pH value. We can measure the pH of a solution using a pH meter. The equation for the calculation of pH using the free proton concentration is as follows;
pH = -log [H+]
What is Titratable Acidity?
Titratable acidity (TA) is a measure of the total acidity as an approximate value. It means that the titratable acidity gives the sum of free protons and un-dissociated acids in a solution. But, it is an approximation of total acidity because it cannot measure all the acidic species in the solution (total acidity is a more accurate measurement).
The unit of measurement of this parameter is grams per litre (g/L). Further, this acidity gives the total concentration of protons in a solution that can react with a strong base to neutralize the base. Ex: NaOH is a strong base which is commonly used in the measurement of TA.
What is the Difference Between pH and Titratable Acidity?
pH is a measure of the concentration of free protons (H+ ions) in a solution and this parameter is unit-less. Whereas, titratable acidity (TA) is a measure of the total acidity as an approximate value. The unit of measurement for this parameter is grams per litre (g/L). This is the main difference between pH and titratable acidity.
Summary – pH vs Titratable Acidity
pH and titratable acidity are very important parameters in determining the soil quality using a soil solution. The difference between pH and titratable acidity is that the pH measures the concentration of free protons in a solution whereas the titratable acidity is a measure of the sum of free protons and un-dissociated acids in a solution.
Reference:
1. “Titratable Acidity.” Milk The Funk Wiki. Available here
2. “PH.” Wikipedia, Wikimedia Foundation, 2 July 2018. Available here
Image Courtesy:
1.’Power of Hydrogen (pH) chart’By Hans Kirkendoll – Own work, (CC0) via Commons Wikimedia