What Is Back Titration?                    

Back titration is a volumetric analysis technique that is used for adding a reagent to an analyte. There are various conditions when back titration is used. In this post, we will discuss everything about back titration, including the correct back titration method.

What is titration?

Titration is a laboratory process, where one solution is added to another to create reactions under certain conditions. Titration is useful in quantitative analysis and is required to determine the concentration of analyte in acid-base reactions.

Back titration definition

The volumetric analysis of back titration is similar to titration, the only difference is that the concentrate of the analyte is reacted with a known amount of excess reagent. The proper definition of back titration can be given with reference to the Oxford Dictionary. According to the definition, given in the Biochemistry and Molecular Biology section of the Oxford Dictionary, back titration is a volumetric analysis technique where the amount of the reagent is known. The estimation is conducted by adding the known excess amount of reagent to an analyte. Using this volumetric analysis, the unreacted amount of reagent is used to determine the titration. 

Back titration example

As mentioned earlier, back titration is a titration that is performed in reverse. A suitable example of back titration is to determine the amount of acetylsalicylic acid in aspirin. In our day to day lives, back titration examples can be found in the food industry. The back titration process is used to determine the amount of salt or sugar in a food product.

Use of back titration

Back titration is performed when direct titration is not feasible. For instance, when the rate of reaction is slow and the colour change is slow, it indicates that a back titration is required for precise analysis. Moreover, in cases where the standard solution lacks stability, back titration becomes a viable choice.

Back titration method: top things to consider

There are certain principles that need to be followed to perform back titration:

1. Add the excess amount of reagent to an analyte.
2. Wait and allow the reagent to react with the analyte.
3. Titrate the remaining reagent with the second analyte.

It is very important to add a precise volume of reagent for the back titration process. Make sure the amount of reagent is known for successful back titration.

It is possible to carry out back titration of a reagent which is a common titrant. Keep in mind that prior to the back titration, you will require to perform standardization of the reagent.

In order to calculate the result of the back titration, you require to understand the stoichiometric reactions. The formula used for calculating the back titration with a blank is to subtract the volume of the equivalence point from the blank determination from the volume at the equivalence point and then multiply it with the nominal titrant concentration, titer factor of the titrant, stoichiometric ratio, and molecular weight of analyte, and divide by the weight of the sample and then multiply by 100.

What is the use of a titrator?

Back titration is a complicated procedure as it involves certain conditions and the calculations also take time. Modern day innovations have made it possible to perform back titration with utmost precision and accuracy. You can use modern titrator devices which are capable of automatic calculations. These high end devices are used in laboratories to quickly calculate the result of back titrations. Full traceability is possible in using modern titrators as they store information concerning the used variables. With the modern range of auto-titrators, the resolution of 10,000–100,000 steps can also be achieved easily.

Bottom line

To conclude, back titrations also follow the principles applied for general titrations, however, there are conditions when standard titrations are not feasible and back titrations become necessary. To calculate back titrations precisely, you need to keep the stoichiometric reactions in mind. Moreover, using a modern titrator makes the entire process of back titration and calculation hassle free. Considering the benefit of a higher range of resolutions, automated titrators are more accurate and precise as compared to manual back titration.

Also Read: Everything You Need To Know About Measuring Cylinders