Boric Acid Titration Curve: Understanding The Basics

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Boric acid is an important chemical compound used in a variety of industries, including pharmaceuticals, cosmetics, and agriculture. It is also commonly used in the laboratory as a reagent for analytical purposes. One of the most important analytical techniques used to determine the concentration of boric acid in a solution is titration.

What is Titration?

Titration is a process used to determine the concentration of a solution by adding a known volume of another solution of known concentration until the reaction is complete. At the point of completion, the concentration of the unknown solution can be calculated using the stoichiometry of the reaction.

Titration Curve of Boric Acid

When titrating boric acid, the pH of the solution changes as the titrant is added. This change in pH can be plotted against the volume of titrant added to create a titration curve. The titration curve of boric acid is unique because it has two inflection points, which are caused by the presence of two acid dissociation constants (pKa) for boric acid.

Inflection Points

The first inflection point occurs when the solution reaches the pH of the first pKa of boric acid, which is 9.24. At this point, the majority of boric acid has been converted to the borate ion. The second inflection point occurs at a pH of 12.46, which is the pH of the second pKa of boric acid. At this point, all of the boric acid has been converted to the borate ion.

Tips for Accurate Titration

To ensure accurate titration results, it is important to use high-quality reagents and equipment. The titrant should be added slowly and with constant stirring to ensure homogeneous mixing. The endpoint of the titration should also be clearly defined, either by using an indicator or by monitoring the pH of the solution.

Applications of Boric Acid Titration

Boric acid titration is commonly used in the pharmaceutical industry to determine the concentration of boric acid in eye drops, which are used to treat eye infections and inflammation. It is also used in the analysis of natural waters and in the production of fertilizers.


In conclusion, boric acid titration is an important analytical technique used to determine the concentration of boric acid in a solution. The unique titration curve of boric acid, with its two inflection points, requires careful attention to detail to ensure accurate results. With proper technique and equipment, boric acid titration can be a valuable tool in many industries.