Due to the presence of iodiniodometry and iodimetry are often confused. These words are often used in iodine titrations to determine the concentration of an analyte under examination. The main difference between iodometric and iodimetric titration is that iodometric titration is a method of indirect titration, whereas iodimetric titration is a method of direct titration.

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Titration

Titration is the process of determining how much of a material is present in a known volume of a substance. Titration may be defined as the process of changing the colour of a substance that has been dissolved in a liquid and then determining the concentration of the substance based on the colour change.

Types of Titration

• Acid-base titration

• Redox titration

• Gas-phase titration

• Complexometric titration

• Zeta potential titration

• Assay

Note- iodometric and iodimetric titrations are types of redox titrations. 

To understand the difference between Iodometric and Iodimetric titration, it is imperative to know what each term means. 

Iodometric Titration

Iodometric titration is an indirect titration method in which the amount of iodine used is measured, which was used prior to the redox titration, through the means of a separate titration. 

The iodometric titration experiment is done to figure out how much analyte is utilised to make iodine. When the amount of oxidising agents in a body of water has to be measured, this experiment is fairly popular.

Iodides react with another oxidising agent in an acidic or neutral media in iodometry. Iodide (which we add in the form of KI) oxidises iodine during this reaction, while the other species are reduced by iodide. The released iodine can then be titrated using another species. The titrating species is a common reducing agent solution capable of converting iodine to iodide form. For this, we usually utilise a normal thiosulphate solution. For example, if we wish to determine the quantity of chlorine soluble in a mixture, we can use the iodometric titration technique.

To begin, we must transfer a known volume of the mixture (in which chlorine is soluble) to a titration flask. The volume consumed may then be determined by titrating it with a known KI solution.

The redox reaction will take place in the reaction flask after that.

2 Cl– + I2 —> Cl2 + 2I–

Then, using the same combination, we should conduct another titration to measure the amount of iodine released. To do so, we can use a normal thiosulphate solution to titrate the combination. To ascertain the reaction’s endpoint, we’ll need to add starch as an indication. The combination will seem dark blue when there is iodine in it, but once all of the iodine has been used up, the dark colour will fade away.

I2 + 2 S2O32− → S4O62− + 2 I–

We can calculate the quantity of Cl2 using the results of the two titrations above.

Iodimetric Titration

Iodimetry is a type of direct titration, the reducing agent has to be an analyte.  Only a good indicator should be used for titration using a standard iodine solution.

Iodimetry is a technique that involves titrating free iodine with a reducing agent. As a result, iodine decreases to iodide and oxidises other species.

Because a free iodine solution is difficult to obtain, we must combine iodine with potassium iodide and KI3 solution to get the needed solution. For iodometric titrations, a standard solution of this is employed.

KI+I2    →   KI3

When titrating, the following response occurs. We may also utilise starch as an iodometric titration indicator. 

I2 + reducing agent → 2 I

Iodometric and Iodimetric Titration: Difference 

Iodometric and Iodimetric Titration: Primary Differences

1. Iodometry is a titration in which the reducing agent is utilised to titrate the iodine formed in the preceding redox reaction, whereas iodimetry is a titration in which the reducing agent is used to titrate the iodine solution directly.

2. Iodometry is a method of indirect analysis, whereas iodimetry is a form of direct analysis.

3. Iodometry involves two redox reactions, whereas iodimetry only requires one.

4. In iodometry, the iodine is oxidised first and subsequently reduced by the reducing agent, but in iodimetry, the iodine is instantaneously reduced.

5. Iodometry is used in many experiments, whereas iodimetric titrations are used less frequently.

6. Quantifying oxidising compounds is done with iodometry, whereas quantifying reducing agents is done with iodimetry.

Conclusion

Although the names iodometry and iodimetry seem similar, they represent two distinct analytical chemistry methods. The main distinction between iodometry and iodimetry is that iodometry may be used to measure oxidising agents whereas iodimetry can be used to measure reducing agents.