Titration is a common method in chemistry to determine the concentration of an unknown solution by using a known solution. A burette is used to add the known solution to the unknown solution until a neutral pH or a color change is observed. The process is repeated multiple times to obtain accurate results.
Titration is a method commonly used in chemistry laboratories and classrooms, which uses a solution of known concentration to analyze and determine the unknown concentration of a second solution. Often the solution whose properties are known is a base, i.e. it has a pH value higher than 7, while the unknown solution is an acid, i.e. its pH is lower than 7. A typical example involves the gradual addition of base to the acidic solution, until a neutral pH of 7 is reached, or until a pH indicator takes on a certain colour, indicating that some other known pH has been reached. This can only be done with aqueous solutions of compounds.
A textbook setup for an acid-base titration has the solution of known strength, called the titrant, suspended in a burette over a flask containing the unknown solution, or titrand. The burette is a vertical calibrated tube with a stopcock at the bottom to regulate the flow of titrant into the flask. The stopcock on the burette is opened, allowing titrant to drip into the flask. When this is closely monitored, it is easy to tell at what point the pH indicator in the acid changes colour, marking the end of this stage of the experiment.
The first time the process is done it is something like a test run, to roughly determine the volume of titrant needed to change the color of the indicator. This volume is recorded, but will not be taken into account in the final results. At this point three more experiments are performed, this time taking into account the amount that was required the previous time to obtain the desired result. It’s best to do this slowly and carefully, to ensure that the results of the experiment are as accurate as possible.
Sometimes, it is helpful for the person performing the test to record the volume displayed on the burette when they think they have reached their endpoint, then test the effect of another drop of titrant to see if the indicator changes color further. If it does, it means it passed the endpoint and its first value was correct, or it may not change color, meaning more titrant may still be needed. After each of these three trials, the burette readings are recorded, indicating the volume required to titrate the solution in the flask. These values are averaged together to receive the result of the experiment, which can then be used to mathematically derive the concentration of the solution in the flask.
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