Titration is the most popular quantitative and volumetric laboratory technique for determining the unknown concentration of an analyte by comparing it to the known concentration of a solution in the presence of an indicator. There are several types of titrations, such as acid-base titrations, redox titrations, precipitation titrations, and complexometric titrations, depending on the goals and process.
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Complexometric titration, also known as chelatometry, is a type of volumetric analysis in which the endpoints are determined by colored substances. In these titrations, an indicator is employed to indicate the titration's endpoint, which is based on the development of a complex between the solute and the titrant.
An example of complexometric titration is the determination of water hardness using EDTA and Eriochrome Black-T as indicators. Direct, back, replacement, and indirect complexometric titration are several types of complexometric titration.
What is back titration?
Back titration is a minimal two-step process in which the titrand is reacted with a specific, excess amount of titrant whose concentration is known. Rather than titrating the original sample, a known excess of the standard reagent is added to the solution, and the titration is performed. The standard titrant will then react with the solute, and the excess remains in the sample solution. The remaining amount of standard reagent can be determined using a back-titration.
“Back titration is a kind of titration that is performed in reverse and is also known as an indirect titration”
Back titration example:
Determination of acetylsalicylic acid in aspirin and determination of phosphate concentration by titration of excess silver nitrate with potassium thiocyanate are examples of back titration.
When is a back titration used?
- Back titration is performed when the reaction between the analyte and the titrant is slow or the analyte is in an insoluble solid
- When the molar concentration of an excess reactant is known but the strength or concentration of a molecule is unknown
- When the acid or base is an insoluble salt
- While determining the endpoint of a direct titration can be difficult, for example, titration of a weak acid and weak base
- When a standard titration fails to find an endpoint, back titration is used
How is a back titration performed?
A back titration usually takes place in two steps: the volatile analyte reacts with an excess reagent first, and then a titration is performed on the remaining quantity of the known solution. It is a way of measuring the amount consumed by the analyte, by calculating the excess quantity.
What is direct titration and back titration?
A back titration involves adding an excess of standard titrant to the solute and titrating the excess titrant to determine how much is in excess, whereas a direct titration directly measures the concentration of the unknown compound, which involves adding a standard titrant to the analyte until the endpoint is reached.
What is back and blank titration?
Back titration is a titration that is carried out in reverse and is also known as an indirect titration, whereas a blank titration is a titration performed on a solution that is identical to a sample solution except that the analyte is not present, which is used to detect and correct systematic analysis errors.
What is the difference between titration and back titration?
In a titration, we normally add a chemically equal amount of standard solution to the analyte, while in a back titration we add an excess amount of standard solution to the analyte. Back-titrations are similar to normal titrations in that they follow the same general principles.
Advantages of back titration:
- It does not need any special chemical or apparatus.
- It can offer correct results.
- It is advantageous when trying to figure out the amount of acid or base is in a non-soluble solid.
- The process is easy to perform, similar to normal titration.
- If the reverse titration endpoint is easier to identify than the normal titration endpoint, this method is useful.
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